text:
Can I make an alcohol-based stain from a pigment with an alkaline extraction process?
I'm in a situation where I don't really even know enough to know if what I want makes sense or has the kinds of problems that I think it might have, but here's the situation:
I would like to make a wood stain out of black walnut hulls. The extraction process seems to involve soaking or possibly boiling in water. Adding a base helps the pyrogallol in the hulls oxidize to brown, which is what I want. (Edit:) At the moment I am using sodium carbonate (baked baking soda) as my base, since it was easy to make and relatively safe, compared with lye or ammonia.
This will be used in combination with shellac, which must be dissolved in alcohol. I would like to either apply the stain to the wood under the shellac, or have the option of mixing the pigment into the shellac. For this it would be ideal if the pigment were in an alcohol solution to avoid diluting the shellac. Furthermore, I found one sketchy source which implied that mixing baking soda and isopropyl alcohol might release harmful gasses, so if that might be a concern, I want to avoid having any dried alkaline salts on the wood when I add alcohol-based shellac on top.
I would ideally like to do this with commonly available materials, and as benign as possible. I have denatured alcohol and everclear available, and all the normal grocery/hardware store stuff.
The specific questions I most need help with are:

Will the sodium carbonate (either dry on the wood surface or in water solution) create any harmful side products if mixed with alcohol (at least 90% ethanol in everclear or denatured alcohol)?
Is there are a way to move the pigment from a water solution to an alcohol solution?

Any advice, help, process, or warnings that I'm going to off myself with fumes would be greatly appreciated. Thanks!


text:
2D NMR of a Funky Disaccharide
Below you'll find the structure of the disaccharide and three 2D NMR spectra - COSY, HSQC, HMBC. I have to match the signals in the spectra to the nuclei that caused them. Answers to any subset of the following questions would be very helpful, but please explain like I'm 5:

How many protons would we expect the protons at A6 (highlighted in orange) to couple with?

Would we expect any coupling between the protons at A1 and B4 (in yellow)?

How many protons would we expect the protons at B6 (in green) to couple with? And are they considered axial or equatorial?

How many protons would we expect the proton at B1 (in blue) to couple with?

How do the heteronuclear spectra help us in this specific case? What is the crucial piece of information that they provide?

The structure:

COSY:

HSQC:

HMBC:

It is not helpful if an atom numbering is ambiguous (e.g., C4 left saccharide binds to an acetate, C4 right binds to an ether [glycoside]). A $|^3J_\text{H,H}|$ often is resolved (H6a, or H6b to chiral H5; either side), a $|^4J_\text{H,H}|$ (still across bonds) typically is much smaller; and both different to coupling through space (NOE). Does your instrument routinely resolve a $^4J_\text{H,H}$? Do you have «an anchor» to work through the space (Sudoku like), best if already known by an assigned precursor which was not altered by the last reaction from literature/own records (e.g., CHBr)?

@Buttonwood This is simply homework that I posted exactly as I have been given it (minus the questions and highlighting, these are my own). To be honest, I don't even understand your 2 questions as anything chemistry-related is quite foreign to me, hence the explain-like-I'm-5 plea.

Answer time!

A6a and A6b (in orange) actually give rise to two separate signals. A6a couples with A5 and A6b; A6b only couples with A6a.

We do not expect any coupling between A1 and A4 because of the O in between.

Again, B6a and B6b (in green) are two separate signals. B6a only couples with B6b; B6b couples with B6a and B5.

B1 only couples with B2.

Below is the correct assignment for COSY, with the signals from ring A and ring B highlighted, resp. Ignore the highlighting if it makes things more confusing, and ask any questions that you might have and I'll try to answer.

"How do the heteronuclear spectra help us in this specific case? What is the crucial piece of information that they provide?" Any comments? You did not show us the assignment for those spectra.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
HCN reactor design
For my diploma work, I should design a hydrogen cyanide (HCN) producing reactor.
I found that for the BMA process, overall
$$\ce{CH4 + NH3 -> HCN + 3 H2 \quad{} \Delta{}H_r = \pu{251 kJ / mol} }$$
Also, there is side reaction of ammonia decomposition.
the decomposition of ammonia is the rate-limiting step. So I should consider it to find the reactor volume. Besides Langmuir - Hinshelwood model, I also found power law rate to calculate the parameter manually. The expression is like this:
r = 2.27 * 10^23* exp (-21000/RT)*P(NH3)
Previously, I have used plug-flow design (PFR) equation which integrates dx/-r, where r is expressed in terms of x - concentration.
However, I do not know how to work with the previous equation, how to relate with conversion. And I am not sure about how to get the design parameter from it. My question is how this kind of power law rate expressions with pressure instead of concentration should be used in design equations?
Any contribution is highly appreciated. Thanks in advance

What are the units  of $r$ and of $\pu{2.27 10^{23}}$. Is $21000$ in Joules ? $\pu{10^{23}}$ is an extremely high number. Is it expressed in molecules per second and $\pu{m^3}$ ?

I will lead you to the general equation. We can relate the partial pressure of a species with conversion by using a simple stoichiometric table.

The reaction is
$$ \ce{NH3(g) + CH4(g) -> HCN(g) + 3H2(g)} $$
$$ \ce{A(g) + B(g) -> C(g) + 3D(g)} \tag{R} $$
where we defined for convenience new letters for all the species. We concentrate on $\ce{A}$.
1. Mole balance
For a PFR the volume needed to achieve a conversion $X_\ce{A}$ is
\begin{equation}
  V = \int_0^{X_\mathrm{A}} \frac{F_\mathrm{A0} \; \mathrm{d}X_\ce{A}}
                                  {-r_\ce{A}(X_\ce{A})} \tag{1}
\end{equation}
where $F_\mathrm{A0}$ is the inlet molar flow rate of species $\ce{A}$ in $\pu{mol s^-1}$
2. Rate law
We have a power law in the form of
$$ -r_\ce{A} = kp_\ce{A} \tag{2} $$
3. Stoichiometry
We set up a stoichiometric table for reaction $\ce{R}$ in terms of the molar flows. For a general species $j$ in a reaction where $\ce{A}$ is the limiting reagent, the molar flow rate of species $j$ is
$$ F_{j} = F_\mathrm{A0} (\Theta_j + \nu_j X_\ce{A}) \tag{3} $$
where $\Theta_j = F_{j0}/F_\mathrm{A0}$ is the molar relation of species $j$ with respect to $\ce{A}$ at the entrance of the reactor, and $\nu_j$ is the stoichiometric coefficient of species $j$.
For the reaction to take place, we need the presence of $\ce{A}$ and $\ce{B}$. Considering that there are no products at the reactor inlet, application of Eq. (3) to reaction $\ce{R}$ gives
\begin{align}
   F_\ce{A} &=  F_\mathrm{A0}(1 - X_\ce{A}) \tag{4} \\
   F_\ce{B} &=  F_\mathrm{A0}(\Theta_\ce{B} - X_\ce{A}) \tag{5} \\
   F_\ce{C} &=  F_\mathrm{A0} X_\ce{A} \tag{6} \\
   F_\ce{D} &= 3F_\mathrm{A0} X_\ce{A} \tag{7} \\
\end{align}
where the total molar flow rate is
\begin{align}
  F_\ce{T} &= \sum_j F_j \\
  F_\ce{T} &= F_\mathrm{A0}(1 - X_\ce{A}) + F_\mathrm{A0}(\Theta_\ce{B} - X_\ce{A}) +
              F_\mathrm{A0} X_\ce{A} + 3F_\mathrm{A0} X_\ce{A} \\
  F_\ce{T} &= F_\mathrm{A0}(1 - X_\ce{A} + \Theta_\ce{B} - X_\ce{A} +
                            X_\ce{A} + 3X_\ce{A}) \\
  F_\ce{T} &= F_\mathrm{A0}(1 + \Theta_\ce{B}  + 2X_\ce{A}) \tag{9} \\
\end{align}
Remembering that the partial pressure of species $j$ is given by
$$ p_j = y_j p = \frac{F_j}{F_\ce{T}}p \tag{10}$$
we combine Eqs. (4), (9), and (10) so that
\begin{align}
  \require{cancel}
  p_\ce{A} &= \frac{\cancel{F_\mathrm{A0}}(1 - X_\ce{A})}
                   {\cancel{F_\mathrm{A0}}(1 + \Theta_\ce{B}  + 2X_\ce{A})}p \\
  p_\ce{A} &= \left(\frac{1 - X_\ce{A}}{1 + \Theta_B  + 2X_\ce{A}}\right)p \tag{11}
\end{align}
4. Design equation
Combining Eqs. (1), (2), and (11) gives the final result
\begin{equation}
  \boxed{V = \int_0^{X_\mathrm{A}} \frac{F_\mathrm{A0} \; \mathrm{d}X_\ce{A}}
  {k\left(\dfrac{1 - X_\ce{A}}{1 + \Theta_\ce{B} + 2X_\ce{A}}\right)p}} \tag{12}
\end{equation}

References
An excellent explanation for stoichiometry for liquid-phase and gas-phase reactive systems  can be read at Chapter 3 of:

Elements of Chemical Reaction Engineering, H. S. Fogler, 5th ed., Prentice Hall (2016).

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Evolution of distillation system over time
In my example, suppose we had a system of multiple components (benzaldehyde, benzyl alcohol, methyl benzoate) and wanted to separate the mixture using fractional distillation.
If we rule out any azeotrope formation, then the components should all be separable completely if the column is good enough right?
Also, suppose we collect a fraction in a vacuum distillation at 60 °C (bath temperature) with a head (thermometer) temperature of 33 °C. We collect some of it, but after time, it would stop and we have to increase the bath temperature (lets say 65 °C) to be able to continue to collect the 33 °C fraction (which stays at 33 °C). That’s because the boiling point of the initial mixture goes up and we distill the most volatile compound off.
But if the separation is good enough, we should be still able to get out the pure product out of this fraction because the head temperature hasn’t changed and it’s the same compound right?

Rather, good enough columns lead to pure enough products (individual ones or azeotropes).

But we have to increase the bath temperature continously to get all of the same fraction (33 °C) out right? As long as the head temperature remains constant it should be the same compound/azeotrope?

Mathematically, assuming matter continuity, the purity converges to 100% for infinite number of "column trays". Practically, good enough for good enough, as above.


text:
Water is removed by distillation to speed up dehydration. Why would that not work for the dehydration of 4-methyl 2-pentanol?
I understand that due to LeChatelier's principle, the removal water forces the reaction to move forward and make more to get back to equilibrium. However, I'm not sure why this would not work for this dehydration.

You need catalytic acid to get the water to leave the 4-Me-2-pentanol before you remove it from the reaction mixture

Can you elaborate more on your reaction set up? What is the evidence that it doesn't work?

Also note that contrary to the wording of your question, removing water does not speed up dehydration. Rather, it slows down rehydration.

Physical dehydration has nothing to do with chemical dehydration, which is a change, a loss of water on the molecular level.


text:
How to regenerate indium wires for vacuum seals?
I have a setup consisting in a vessel that eventually gets at low temperatures (approximately 85K - 87K) and needs indium wire as sealant. Unfortunately, we have to frequently open and close this setup to replace the internal components under test or measurement and I was wondering whether I could recycle the used indium.
In particular, I know that a former colleague was melting it inside a vial on a flame, together with citric acid powder pre-melted in the same vial. After this melting he was remaking the wire by simple extrusion.
Now the main questions are the following: has onyone ever heard about this "in house" process? Does anyone know the role of the acid? Is it used just to avoid oxydation during the melting stage?
Also, has anyone some reference (scientific articles or reviews) on the techniques for the regeneration of used indium gaskets/o-rings (not from electronic scrapes)?
Thank you so much for any answer.

I knew people who just hand rolled them back to being fat enough to compress again. The Indium corporation used to recycle your old wire and give a credit for new wire. Not sure about these days. All depends how cheap you want to go.

Thank you Jon for your answer. Actually, we open the vessel up to 3 times a week for replacing the internal setup. At the moment we seal il with an ISO flange with viton gasket. It is great untill we do not cool down the internal argon to liquify it. At that point is very difficult to avoid that the external air leaks in the chamber and spoil the purity argon (below the ppm). So, I thought that it would be great to modify the sealing with indium instead of redesigning from scratch the entire setup.


text:
N2 HOMO-LUMO Gap calculation
I am thinking about calculating the HOMO-LUMO energy gap for $\ce{N2}$ molecule.
I thought I could model this as a particle in a box problem to find $E_\text{HOMO}$ and $E_\text{LUMO}$.
The formula I used was $E_n  =  \frac{h^2 n^2}{8 m_e L^2}$
I put in $L$ as the bond length of nitrogen. This gave me the wrong results. I hear this kind of thing works for conjugated molecules, and I thought it would work for $\ce{N2}$.
Is there a simple hack of this variety that can be used to calculate this or generate a short table of such transitions?
I think DFT is good for ground state-related affairs and besides needs a bit more setting up.
Is there also maybe a reference that does this kind of thing for $\ce{N2}$ molecule nicely with full detail? I want to use the differences to predict the wavelengths to be observed by UV spectroscopy by $\Delta E = h \frac{c}{\lambda}$.
I have to put my pride to the side and also trust that this is a nice good safe space for my code.
Here is what I have tried. I wanted to calculate the ground states, but it is not quite working. Also, I think the simple 1-d DFT only gets the ground state, so my scheme of doing E[1] - E[0] is wrong.
I probably need to upgrade this to TDDFT.
I want to plot transition probabilities vs wavelength at the end.
This code is written in Python. Can someone help with the missing pieces?
I have now attempted to generate excited states using ordinary perturbation theory from the ground states.
It generates a plot but it is not showing the trend I would expect. I expect the HOMO-LUMO Gap to fall, but it is not falling.
My code is wrong? Or my chemistry is horrible.
About the chemistry, I hacked my way to try to create an approximation of the TD DFT without time.
# Kevin Njokom
# Written completely from scratch

import numpy as np
import matplotlib.pyplot as plt
import numpy.linalg  as linear_algebra
import math as math
import periodictable as elements

# Units
# hbar = e = m = 1

# constants
# number_of_electrons = 14  # Number of electrons
size = 50 #150  # Number of grid points (increased for accuracy) # at least 4
tolerance = 1e-40  # A small epsilon
max_iterations = 100

# Constants
h = 6.62607015e-34  # Planck's constant in J s
c = 299792458       # Speed of light in m/s
au_to_joules = 4.35974417e-18  # Conversion factor from atomic units to joules
angstrom_to_meter = 1e-10  # Conversion factor from angstroms to meters

# Global lists

delta_Energy_keeper =[]
psi_ground_keeper =[]
psi_excited_keeper = []

Vectoria_2 = []
Excited_energy_2 = []

def give_me_angstroms(energy_au):
    # Convert energy from atomic units to joules
    energy_joules = energy_au * au_to_joules
    # Calculate wavelength in meters
    wavelength_meter = h * c / energy_joules
    # Convert wavelength to angstroms
    wavelength_angstrom = wavelength_meter / angstrom_to_meter
    # trying something
    return wavelength_angstrom

# Finite difference approximation for the second derivative implemented in code

def create_second_derivative_operator(size):

    # Create the main diagonal
    main_diag = np.ones(size) * -2

    # Create the sub-diagonals
    sub_diag = np.ones(size-1)

    # Construct the tridiagonal matrix
    second_derivative_operator = np.diag(main_diag) + np.diag(sub_diag, k=1) + np.diag(sub_diag, k=-1)

    return second_derivative_operator

# Definition of the Reimann Integral implemented in code

def reimann_integration(x_co_ordinate, function_to_integrate):
    finite_difference =x_co_ordinate[1] - x_co_ordinate[0]
    Integrate = np.sum(function_to_integrate * finite_difference)
    Integrated = Integrate
    return Integrated

# This normalizes a vector

def vector_normalization(vector):
    magnitude = np.linalg.norm(vector)
    normalized_vector = vector / magnitude
    return normalized_vector

# poisson equation solver
# second_derivative_operator * potential  = electron density

def poison_equation_solver( second_derivative_operator, electron_density):
    potential = np.linalg.tensorsolve(second_derivative_operator,electron_density)
    return potential

# create wave function

def create_initial_wave_function(size,number_of_electrons):
    dim = size
    initial_wave_function = np.ones(dim)
    return initial_wave_function

def single_electron_wave_function(size):
    Hamiltonian = -0.5 *create_second_derivative_operator(size)
    eigen_values, eigen_vectors = linear_algebra.eigh(Hamiltonian)
    return eigen_vectors

def single_electron_energies(size):
    Hamiltonian = -0.5 *create_second_derivative_operator(size)
    eigen_values, eigen_vectors = linear_algebra.eigh(Hamiltonian)
    return eigen_values

# each wavefunction is in an orbit
# each contributes a density
# all the densities are added and multiplied by 2
# This is the electron density

def electron_density(vector_of_vectors):
    # Square each element of the vectors and sum them up
    sum_of_element_in_vector_of_square_vectors = np.array(list(map(lambda vec: np.sum(np.square(vec)), vector_of_vectors)))
    return 2*(sum_of_element_in_vector_of_square_vectors)

# Initial electron density guess

electron_density_guess = electron_density(single_electron_wave_function(size))

# Achievement unlocked! I have independently computed the hatree potential alone from scratch! No peeking, no reference!
# Hartree potential here is computed by pseudo -inverse methods

def hartree_potential(size, number_of_electrons):
    eigen_vectors = single_electron_wave_function(size)
    vector_of_normalized_vectors = np.array(list(map(lambda vec: vector_normalization(vec), eigen_vectors)))
    new_electron_density = electron_density(vector_of_normalized_vectors)
    Apinv = np.linalg.pinv(create_second_derivative_operator(size))  # Finds pseudo-inverse
    V_hartree_potential = Apinv.dot(new_electron_density*(np.ones(size)))
    V_hartree_potential = V_hartree_potential*number_of_electrons
    return V_hartree_potential

# Exchange potential

def exchange_potential(size, number_of_electrons):
    eigen_vectors = single_electron_wave_function(size)
    vector_of_normalized_vectors = np.array(list(map(lambda vec: vector_normalization(vec), eigen_vectors)))
    new_electron_density = electron_density(vector_of_normalized_vectors)
    V_exchange_potential  = -(3. / np.pi * new_electron_density)**(1. / 3.)
    return V_exchange_potential

def complete_hamiltonian_with_interaction(size, number_of_electrons):
    kinetic_contribution = -0.5 *create_second_derivative_operator(size)
    complete_hamiltonian_with_interaction = -0.5 *kinetic_contribution + np.diagflat(hartree_potential(size,number_of_electrons)) + np.diagflat(exchange_potential(size,number_of_electrons))
    eigen_values,eigen_vectors = linear_algebra.eigh(complete_hamiltonian_with_interaction)
    return eigen_vectors

def complete_hamiltonian_with_interaction_energies(size, number_of_electrons):
    kinetic_contribution = -0.5 *create_second_derivative_operator(size)
    complete_hamiltonian_with_interaction = kinetic_contribution + np.diagflat(hartree_potential(size,number_of_electrons)) + np.diagflat(exchange_potential(size,number_of_electrons))
    eigen_values,eigen_vectors = linear_algebra.eigh(complete_hamiltonian_with_interaction)
    return eigen_values

def print_separator(character='-', length=50):
    separator = character * length
    print(separator)

def make_matrix(omega, size):
    # Create a matrix of zeros of size size by size
    mat = np.zeros((size, size))
    # Set diagonal elements to -omega
    np.fill_diagonal(mat, -omega)
    return mat

def matrix_form_solve_for_x_Ax_omega_x(vector1, vector2, vector3):
    # Perform the matrix multiplication vector1 . matrix
    Omega_number = np.dot(vector1[0], vector3[0])
    # Perform the matrix multiplication result1 . vector2^T
    Omega_number = Omega_number * vector2[0]
    return Omega_number  #Actually, this is a number

def self_consistency_loop(size, number_of_electrons, max_iterations):
    electron_density_guess = electron_density(single_electron_wave_function(size))
    nuevo_eigen_vectors = complete_hamiltonian_with_interaction(size, number_of_electrons)
    normalized_nuevo_eigen_vectors = vector_normalization(nuevo_eigen_vectors)
    nuevo_electron_density = electron_density(normalized_nuevo_eigen_vectors)
    old_electron_density = electron_density_guess
    Energetica = []
    Vectoria = []
    leading_energy_correction = []
    leading_energy_correction_2 = []
    iteration = 0

    while iteration < max_iterations:
        if abs(nuevo_electron_density[0] - old_electron_density[0]) < tolerance:
            print("new electron density" + " " + str(nuevo_electron_density[0]) + "\n")
            print("convergence achieved" + "\n")
            print("Energies" + str(Energetica) + "\n")
            print("Energy Difference" + " " + str(Energetica[1] - Energetica[0]) + "\n")
            print("tolerance to within " + str(abs(nuevo_electron_density[0] - old_electron_density[0])) + "\n")
            print("Iteration number " + str(iteration) + "\n")
            print_separator()
            leading_energy_correction = matrix_form_solve_for_x_Ax_omega_x(Vectoria,V_exchange_potential,Vectoria)
            leading_energy_correction_2.append(matrix_form_solve_for_x_Ax_omega_x(Vectoria,V_exchange_potential,Vectoria))
            sorted_Energies = sorted(Energetica)
            Excited_energy_n, Excited_state = linear_algebra.eigh(make_matrix(leading_energy_correction + sorted_Energies[0],size))
            delta_Energy = leading_energy_correction
            delta_Energy_keeper.append(delta_Energy)
            diff_now = delta_Energy_keeper[-1]
            wavelength_lambda = give_me_angstroms(diff_now)
            delta_Energy_keeper.append(delta_Energy)
            psi_ground_keeper.append(Vectoria[0])
            psi_excited_keeper.append(Excited_state[0])
            prob_trans = (np.dot(psi_ground_keeper[-1], psi_excited_keeper[-1]))**2
            wavelength_lambda = give_me_angstroms(abs(diff_now))
            return [wavelength_lambda, prob_trans, diff_now]

        # Update the electron density and energies if the convergence criterion is not met
        old_electron_density = nuevo_electron_density
        V_exchange_potential = -(3. / np.pi * old_electron_density) ** (1. / 3.)
        Apinv = np.linalg.pinv(create_second_derivative_operator(size))
        V_hartree_potential = Apinv.dot(old_electron_density * (np.ones(size)))
        V_hartree_potential = V_hartree_potential * number_of_electrons
        kinetic_contribution = -0.5 *create_second_derivative_operator(size)
        newestHamiltonian = kinetic_contribution + np.diagflat(V_hartree_potential) + np.diagflat(V_exchange_potential)
        new_Energies, nuevo_eigen_vectors = linear_algebra.eigh(newestHamiltonian)
        Energetica = new_Energies
        Vectoria = nuevo_eigen_vectors
        normalized_nuevo_eigen_vectors = vector_normalization(nuevo_eigen_vectors)
        nuevo_electron_density = electron_density(normalized_nuevo_eigen_vectors)

        print("new electron density" + " " + str(nuevo_electron_density[0]) + "\n")
        print("convergence not achieved" + "\n")
        print("Energies" + str(Energetica) + "\n")
        print("Iteration number " + str(iteration) + "\n")
        print("tolerance to within " + str(abs(nuevo_electron_density[0] - old_electron_density[0])) + "\n")
        print_separator()
        print(Vectoria)

        iteration += 1  # Increment iteration after convergence check and updates
        print("Energy  = "+ str(np.min(Energetica)) +" " + "for iteration number" + " " + str(iteration))

# Define dictionary mapping atomic numbers to element symbols
atomic_number_to_symbol = {1: 'H', 2: 'He', 3: 'Li', 4: 'Be', 5: 'B', 6: 'C', 7: 'N', 8: 'O', 9: 'F', 10: 'Ne',
                           11: 'Na', 12: 'Mg', 13: 'Al', 14: 'Si', 15: 'P', 16: 'S', 17: 'Cl', 18: 'Ar',
                           19: 'K', 20: 'Ca', 21: 'Sc', 22: 'Ti', 23: 'V', 24: 'Cr', 25: 'Mn', 26: 'Fe',
                           27: 'Co', 28: 'Ni', 29: 'Cu', 30: 'Zn', 31: 'Ga', 32: 'Ge', 33: 'As', 34: 'Se',
                           35: 'Br', 36: 'Kr', 37: 'Rb', 38: 'Sr', 39: 'Y', 40: 'Zr', 41: 'Nb', 42: 'Mo',
                           43: 'Tc', 44: 'Ru', 45: 'Rh', 46: 'Pd', 47: 'Ag', 48: 'Cd', 49: 'In', 50: 'Sn',
                           51: 'Sb', 52: 'Te', 53: 'I', 54: 'Xe', 55: 'Cs', 56: 'Ba', 57: 'La', 58: 'Ce',
                           59: 'Pr', 60: 'Nd', 61: 'Pm', 62: 'Sm', 63: 'Eu', 64: 'Gd', 65: 'Tb', 66: 'Dy',
                           67: 'Ho', 68: 'Er', 69: 'Tm', 70: 'Yb', 71: 'Lu', 72: 'Hf', 73: 'Ta', 74: 'W',
                           75: 'Re', 76: 'Os', 77: 'Ir', 78: 'Pt', 79: 'Au', 80: 'Hg', 81: 'Tl', 82: 'Pb',
                           83: 'Bi', 84: 'Po', 85: 'At', 86: 'Rn', 87: 'Fr', 88: 'Ra', 89: 'Ac', 90: 'Th',
                           91: 'Pa', 92: 'U', 93: 'Np', 94: 'Pu', 95: 'Am', 96: 'Cm', 97: 'Bk', 98: 'Cf',
                           99: 'Es', 100: 'Fm', 101: 'Md', 102: 'No', 103: 'Lr', 104: 'Rf', 105: 'Db',
                           106: 'Sg', 107: 'Bh', 108: 'Hs', 109: 'Mt', 110: 'Ds', 111: 'Rg', 112: 'Cn',
                           113: 'Nh', 114: 'Fl', 115: 'Mc', 116: 'Lv', 117: 'Ts', 118: 'Og'}

# Define lists to store wavelengths and probabilities
wavelengths = [[] for _ in range(20)]
probabilities = [[] for _ in range(20)]
Energy_differences = [[] for _ in range(20)]

# Loop through different numbers of electrons
for num_electrons in range(1, 21):
    # Call self_consistency_loop function
    result = self_consistency_loop(size, num_electrons, max_iterations)
    # Store the result
    wavelengths[num_electrons - 1].append(result[0])
    probabilities[num_electrons - 1].append(result[1])
    Energy_differences[num_electrons - 1].append(result[2])

# Plotting
plt.figure(figsize=(10, 6))
for num_electrons in range(1, 21):
    if num_electrons == 14:
        label = 'Si or N2'  # Label as carbon or nitrogen molecule for 14 electrons
    else:
        label = atomic_number_to_symbol.get(num_electrons, f"Element {num_electrons}")  # Get symbol from dictionary
    # Plot data points
    plt.plot(wavelengths[num_electrons-1], probabilities[num_electrons-1], marker='o', linestyle='', label=label)
    # Add labels for each point
    for x, y in zip(wavelengths[num_electrons-1], probabilities[num_electrons-1]):
        if num_electrons == 14:
            plt.text(x, y, label, fontsize=8, ha='right', va='bottom')
        else:
            plt.text(x, y, atomic_number_to_symbol[num_electrons], fontsize=8, ha='right', va='bottom')

plt.xlabel('Wavelength (Angstrom)')
plt.ylabel('Probability of Transition')
plt.title('Probability of Transition vs Wavelength for Different Numbers of Electrons (atoms or molecules)')
plt.legend(loc='upper center', bbox_to_anchor=(0.5, -0.15), ncol=5)
plt.grid(True)
plt.show()

print("---------------------------------")
print(delta_Energy_keeper)
print("---------------------------------")
print(psi_ground_keeper[0])
print("---------------------------------")
print(psi_excited_keeper[0])
print("---------------------------------")
print(Excited_energy_2)
print("---------------------------------")
print(Energy_differences)
print("---------------------------------")

While it is an interesting idea I suspect a 1 dimensional box is too far from the reality to get anything better than an order of magnitude estimate. But let's soldier on. Could you edit the question to show exactly the maths you did and the result you obtained; the result you  expect with a reference would be useful as well. "The wrong results" really is nowhere near enough, we need to see what you did.

For future reference: for the body of questions, answers, and comments, chemistry.se offers to use mhchem as a comfortable method to add chemical equations and report numerical values (\pu{}) including a non-breakable space.  It should not to be used in the title of a post.

Hello @IanBush , I have now shown progress thus far. I really hope this could maybe happen


text:
Does "concentration gradient" refer to the amount of all solutes, or a specific solute moving across a membrane?
I'm struggling with something that seems really simple, and I think it's because I'm stuck on the definition of concentration gradients.
If you have a solution with a moderate concentration of molecule A crossing a membrane where the other side has no A but a high concentration of molecule B, is A moving up the concentration gradient because there's a higher ratio of solute:solvent, or down because there isn't any molecule A present in that solution?
Thank you!

The concentration gradient is typically used to describe the driving force for mass transport by diffusion. It is going to be the different concentrations of species A that drives species A to move, B can have an influence but typically it is only minor.
So typically when mentioning concentration gradients it is for a specific species/molecule and not for the total concentration of species/molecules. So in your case the species will be going from a high concentration to low concentration of A, i.e. down the gradient.

The solute does not cross the membrane in osmosis. Only the solvant (water for exemple) crosses the membrane. The solute (sugar for example) is dissolved in different concentrations in both solutions. But usually it is dissolved in only one of the two solutions. The other liquid phase is pure solvant.
The membrane has plenty of tiny holes, small enough to allow tiny molecules like water molecules to pass. But the holes are not large enough to allow big molecules of solute (like sugar) to do the same. So these big molecules are partly blocking some holes. Only water can push such big sugar molecules blocking the holes and from the other side cross the membrane. As a consequence, on the long range, water is slowly flowing from the pure solvant (or diluted solution) to the second, more concentrated solution, on the other side of the membrane. And this concentrated solution gets more and more diluted.
The difference of concentration between both sides of the membrane is called the concentration gradient. It goes slightly decreasing with the time.

The question did not mention osmosis, I think you are answering something that did not get asked. Also, solutes definitely can cross membranes. It depends on the membrane and solute.


text:
Smell of orange peel travels super fast
Many years ago, my college chemistry teacher squeezed an orange peel in the front of the auditorium asking us to raise our hands when we smelled it. Hands rippled through the auditorium (at least 40 rows) very quickly.
I am trying to replicate this but it is not working. I've tried scrubbing the oranges in case they had been heavily waxed but without no luck.
How can I replicate this? Anything else with a strong (but pleasant) odor that can travel through a large theater almost very quickly?

I have done this experiment many times. The smell has always taken some seconds and  minutes to diffuse through the auditorium up to the highest row. It was fast, but never instantaneous. Your auditorium must have had some strange technical way of mixing the air.

Well, either the smell was already dispersed beforehand, or there was a strong updraft of air, or people were less than truthful. BTW smells travel mostly disperse via convection, diffusion itself is much slower.

Aside of possible artificial air convection, I would not underestimate subjective factor. When people are told what they are expected to smell,  they have tendency to smell it in advance.

By "instantaneous", I meant very, very fast, shockingly so - at least to a group of college undergrads.
The few times I've tried it this week,it is not working at all.  No one smells anything, whether asking them in advance or afterwards.

Perhaps the prof had some dedicated fans in that room.

One part of doing good repeated experiments is to control the environment. A large classroom or theatre has many elements that will influence this result so just because it worked somewhere, doesn't mean it will work for you. Perhaps the incoming air in the original theatre was behind the lecturer and blew the scent towards the audience? Perhaps it was a much smaller room? To know how fast the smell travels, you need to control those factors.

The setup confounds chemistry and physics on side (transport of molecules by «normal» air flow because a door/window, sash of a hood is open; convection by a radiator, diffusion by concentration gradient) on one side, with psychology on the other.  The former can be monitored by organisms, and machines.
The later may be more complex.  Over time, we are primed for instance by the taste of a lemon, can develop a response expectancy about the scent associated by other stimuli e.g., sound and sight.  Say you were a sparring partner for the uneven bars; after some training together, don't you equally move while the other performs the exercise -- not only for safety to promptly catch him/her if necessary?  If you usually play an instrument and go to a concert, knowing some of the passages by heart, isn't your brain equally similarly engaged except for the actual play of  the instrument, too?
Placebos play a role in medical research -- even to the degree that there are active placebos intentionally containing ingredients e.g., to cause dizziness in order to prevent de-blinding medical studies because patients can be conditioned to the presence of typical side effects the verum generates -- by the talk with the physician, the leaflet in the package, hearsay.  Why else running blinded and even double-blinded studies where neither patient, nor physician know the content of the box until the end?  Their role is even more prominent (or better, more important) in treatments which are less (or not) evidence based.
And group dynamics like «well if my dear neighbor feels sickened...»  You equally might repeat the experiment, unveil a beautiful container of tap water «I'm so glad to present you a new, exquisite parfum; the first to sense it, gets it for free».

This is a great exaplanation of how and why the effect works, both physically and psychologically.
What I am really after is how to get the audience to smell oranges within, say, 10 seconds of planting the seed in their minds that "I can get them to think of oranges".  (This is for a high school magic show.)


text:
Who is more polar: acetonitrile or methanol?
According to data dipole moment of acetonitrile is around 4 while that of methanol is 1.7 but is said that acetonitrile is more soluble in non polar solvent that methanol.
But shouldn't methanol be more soluble because it has lower dipole moment?

Dipole moment is just one of factors. More important factor is hydrogen bond between methanol molecules, similarly as for water molecules.


text:
Law of multiple proportion fitting in the notion of an atom
I have been reading about atoms. Currently, I am referring to the book "Atom : Journey across the subatomic cosmos" by Issac Asmov.
I believed that if we start dividing something so we can just keep dividing it(not atomist). To prove it to myself, I assumed that if I have the power to scale my self in negative, then I would just may be become 4*(size of item) and divide it and keep on going.
Now, I was introduced to the Law of multiple proportion and the author stated that "it fit the notion of atoms.". And yeah, I proved it to myself this way assuming that mass of element A is fixed(say x) and we take mass of element B as y and z in two reactions.
It is found that :
$$\frac{y}{z} \in Z$$
where Z is a set of Integers.
Suppose, n atoms of A interact with m atoms of B to form some compounds. This implies that y grams of B has $m / y$ atoms and no. of atoms in z grams of B would be : $$m \frac{z}{y}$$Since atoms are in integers, so z : y should be an integer. So, yeah it fits the notion of atoms.
Suppose, I don't know much more than this(I am in this time period when this was discovered).
Do you have any other notion of elements/matter which explains this law of multiple proportion.
Any recommendations on how to understand the developments in the atoms are welcome.

You may find useful reviewing of search results for
site:stackexchange.com OR site:libretexts.org OR site:wikipedia.org OR site:hyperphysics.phy-astr.gsu.edu  law multiple proportions

I suppose the quantal idea of an "atom" is not necessarily implied (the fact that an atom is not divisible into something with the same properties except quantity). A continuum of matter to infinitely small size could be possible, if difficult to explain.

@BuckThorn Can you please explain? I understood that you are talking about something that an atom can be divided into something else also but that might not have the same property as that of an atom.

Well, atoms can be divided into subatomic bits…

Issac Asimov, the professor of biochemistry in Boston,  the famous Sci-Fi writer and the author of The Three Laws of Robotics.  //  Atom: Journey Across the Subatomic Cosmos

Tbh the atomic theory is quite convincing ;) I thought I was onto an alternative but I'm no longer sure it pans out. The catch is of course the required proportionality. My argument is that solids with known properties (eg crystalline) have to exist in given proportions, according to the law, but lacking microscopic information, that proportionality might be exhibited as, for instance, interleaved sheets of elemental substances. But as soon as you start working with gases (presumably also solutions, eg saturated), the argument falters.

https://hsm.stackexchange.com/questions/83/what-were-the-dominant-non-atomic-theories-of-matter-in-the-19th-century

https://chemistry.stackexchange.com/questions/4989/when-did-the-atom-theory-become-indisputable

BTW, not all compounds fall neatly into the law of multiple proportions. If early chemist first investigated intermetallic compounds, or compounds where one element can substitute for another (e.g., alums, double sulfates: https://en.wikipedia.org/wiki/Alum), they could find confounding evidence against the law of definite proportions! Perhaps physics, such as the Millikan-Fletcher oil drop experiment, https://en.wikipedia.org/wiki/Oil_drop_experiment, led more directly to acceptance of atoms.

So, just law of multiple proportion is not enough to convince someone for an existence of atoms. Since, this just FITS the notion of atoms and also it doesn't fit everywhere.

It would be one brick consistent with an atomic theory and not consistent with a number of other theories. A related question is whether there are experiments that would have pointed to the atomic theory being false?

I did not think this way. Were there experiments that proved it false?

Dalton's theory postulated that the atom is indivisible, when in fact it has an internal structure. The existence of electrons, ions, nuclei, isotopes (an internal atomic structure) took another century to uncover.

Yeah, I studied these in school but I am digging into things this time. So, I would consider that when I will study this.


text:
Heat capacity of calorimeter
The problem is:

$\pu{30 mL}$ of water at $\pu{24.00 °C}$ were stored in a calorimeter in a laboratory experiment. Then, $\pu{40 mL}$ of water at $\pu{55.00 °C}$ were added to the calorimeter achieving thermal equilibrium when temperature reached $\pu{40.00 °C}$ in the system. Subsequently, the same calorimeter is used to dissolve $\pu{6.42 g}$ of ammonium nitrate in $\pu{110.00 g}$ of water at $\pu{23.00 °C}$. This new system reaches the thermal equilibrium at $\pu{19.05 °C}$. The specific heat capacity of ammonium nitrate can be considered as $c_\mathrm{s} = \pu{1,6643 J/°C}$. Calculate $\Delta_\mathrm{sol}H$ of ammonium nitrate and heat capacity of calorimeter.

What I did is I calculated the heat of reaction
\begin{align}
  Q_\mathrm{rxn}
  &= mC_\ce{H2O}\Delta T \\
  &= (116.42)(4.18)(19.05 - 23) \\
\end{align}
and I also know that $\Delta_\mathrm{sol}H = Q_\mathrm{rxn} + q_\text{cal}$. However, how do we calculate the heat capacity of the calorimeter?

Formulate the equation with calorimeter capacity as the unknown variable and calculate it's value, leading to the final Tc r 40.00 Deg C.


text:
Why doesn't acid dissociation always have K>1?
Acid dissociation is usually exothermic, and it has an increase in entropy, so the change in Gibbs free energy should be negative. So why isn't always  $K_\mathrm{a}>1$ in accordance with $\Delta G^\circ = -RT\ln K$? For example, when $\ce{H3PO4}$ dissolves, the change in enthalpy is $\pu{-14.2 kJ/mol}$, and the entropy presumably increases, but $K_\mathrm{a} = \pu{7.6E-3}$ (less than 1).
Edit: Apparently acid dissociation doesn't usually increase entropy, so my new question is why that is.

Dissolution and dissociation are different processes. Most of dissolved  H3PO4 is not dissociated

Right, I was trying to talk about dissociation. Edited.

"Acid dissociation is usually exothermic" reference to support this assertion, please

Well in this case it is exothermic

7/8 in the table here: https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Inorganic_Chemistry_(LibreTexts)/06%3A_Acid-Base_and_Donor-Acceptor_Chemistry/6.03%3A_Brnsted-Lowry_Concept/6.3.05%3A_Thermodynamics_of_Solution-Phase_Brnsted_Acidity_and_Basicity

It seems that the reason is that dissociation of H3PO4 doesn't actually increase entropy. But why?

Dissociation is exothermic only if ion hydration is more exothermic than the heterolytic breaking of R-H bond is endothermic.

Note: it's ΔG$^∘$=-RTln(K) not ΔG=-RTln(K).

Solvated ions have a fairly structured shell of water molecules around them which have lower entropy than bulk water. The number of water molecules involved and strength of structure will vary with ion.


text:
Is rate of effusion directly proportional to pressure
From Graham's law of effusion we know that rate of effusion is inversely proportional to square root of density of gas but if two gases are being effused at different pressures then is rate directly proportional to pressure?

Yes, it is proportional for ideal gases. For real gases, there are deviations for high pressures.


text:
Regarding Hinsberg reagent, potassium salt of primary amine soluble in base become insoluble after acidification?

Distinguish between ethylamine, diethylamine and triethylamine by using Hinsberg's reagent?
Ans. This reaction is useful for the distinction of primary, secondary and tertiary amines.
(i) Primary amine (like ethyl amine) is treated with Hinsberg's reagent (benzene sulphonyl chloride) forms N-alkyl benzene sulphonamide which dissolve in aqueous KOH solution to form a clear solution of potassium salt and upon acidification gives insoluble N-alkyl benzene sulphonamide.

(ii) Secondary amine like diethyl amine is treated with benzene sulphonyl chloride forms N,N-diethyl benzene which sulphonyl amide remains insoluble in aqueous KOH and does not dissolve in acid.

So as given in the reaction, when we react N-Ethyl benzene sulphonamide with KOH it form a potassium salt. When the potassium salt is acidified, why is the N-alkyl benzene sulphonamide insoluble when it was earlier soluble?

In what solvent?

Potassium hydroxide solution, presumably

Please substitute images with typed text. You might keep relevant images of structures but at least add typed text.

Why would you expect an organic compound like N-ethyl benzenesulfonamide to be aqueous soluble? The potassium salt is soluble because it is an ionic species, the neutral compound will not be.

@Waylander For the record the schematic reports that the K-salt is insoluble. That might be the source of the confusion.


text:
Partial derivative of the Gibbs free energy with respect to temperature at constant enthalpy
I am trying to find the expression for $\left(\frac{\partial G}{\partial T}\right)_H$ as a function of the entropy $S$, temperature $T$, $C_p$ and $\alpha=\frac1V\left(\frac{\partial V}{\partial T}\right)_p$.
So far from the definition of enthalpy $H=U+pV$ and the differential form of the internal energy equation $\mathrm dU=T\,\mathrm dS-p\,\mathrm dV$ when setting $\mathrm dH=0$ due to the process being isenthalpic, I got that $\left(\frac{\partial T}{\partial S}\right)_p=-\left(\frac{\partial V}{\partial p}\right)_S$ but from this point I got stuck trying to somehow use it in the differential form of the Gibbs free energy equation.

We differentiate the differential form of the Gibbs free energy with respect to the temperature at constant enthalpy
\begin{align}
  \mathrm{d}G &= V\mathrm{d}p - S\mathrm{d}T \\
  \left(\frac{\partial G}{\partial T}\right)_H &=
  V\left(\frac{\partial p}{\partial T}\right)_H - S \\
  \left(\frac{\partial G}{\partial T}\right)_H &=
  \dfrac{V}{\color{blue}{\left(\dfrac{\partial T}{\partial p}\right)_H}} - S \tag{1} \\
\end{align}
and we identify in Eq. (1) the Joule-Thomson coefficient. Replacing it by its known expression leads to the final result after some algebra
\begin{align}
  \require{cancel}
  \left(\frac{\partial G}{\partial T}\right)_H &=
  \dfrac{V}{\color{blue}{\dfrac{1}{C_p}
  \left[T\left(\dfrac{\partial V}{\partial T}\right)_p - V\right]}} - S \\
  &= \dfrac{V}{\dfrac{1}{C_p}
  \left[T\dfrac{V}{V}\left(\dfrac{\partial V}{\partial T}\right)_p -
  V\right]} - S \\
  &= \dfrac{V}{\dfrac{1}{C_p}(T\alpha V - V)} - S \\
  &= \dfrac{\cancel{V}}{\dfrac{\cancel{V}}{C_p}(T\alpha - 1)} - S \rightarrow
  \boxed{\left(\frac{\partial G}{\partial T}\right)_H =
  \dfrac{C_p}{T\alpha - 1} - S}
\end{align}


text:
Is the energy difference between the 2s and 2p orbital smaller than the difference between 3s and 3p?
on this website (https://physics.nist.gov/PhysRefData/ASD/levels_form.html), you can look up atomic spectra. For example, if you query "Na I", you will see that the Level (cm^-1) for the excited state of Sodium (2p63p electron configuration) is approximately 16 956, whereas for the ground state (electron configuration 2p63s) the Level is 0, of course. So far, so good.
But if you query Lithium ("Li I"), you will see that the Level of the excited state is  14 903 (electron configuration 1s22p) as compared to the ground state (electron configuration 1s22s).
Is it wrong for me to deduce that therefore the energy difference between the 2s and 2p orbital in Lithium is smaller than the energy difference between the 3s and 3p orbitals in Sodium? It confuses me because I always thought that it should be the other way around.
I really hope you can help me, thanks in advance!
Best regards
Thies

you have to be careful when making extrapolations. You have to take into account nucleus-electron attraction and electron-electron repulsions. Li has a nuclear charge of +2, and 2 electrons in the nucleus. However, Na has a nuclear charge of +11, 10 core electrons and 1 valence electron. The interactions in the two atoms are very different. You have to compare the energies of atomic configurations which correspond to the same atom.

Thanks for the answer! But I do not extrapolate anything, I just compare two numbers that are showing what I describe in the post. These numbers also explain why the light emitted from Sodium in the flame test has more energy than the light emitted from Lithium. So what I describe seems to be the case, I just do not get it, since I had learned that it should be the other way around.

The general question in the title "Is the energy difference between the 2s and 2p orbital smaller than the difference between 3s and 3p?" is different from the specific question "Is it wrong for me to deduce that therefore the energy difference between the 2s and 2p orbital in Lithium is smaller than the energy difference between the 3s and 3p orbitals in Sodium?".

The energy difference between the s and p orbitals increases with atomic number
As the atomic number increases, the nuclear charge increases and the electrons move closer to the nucleus. This reduces the energy of all orbitals, but reduces the energy of the s orbitals more than the energy of the p orbitals. This is because s orbitals penetrate further into the nucleus and have a higher electron density than p orbitals, so they are more affected by the increase in nuclear charge.
As a result of these factors, the energy difference between the s and p orbitals increases with atomic number, just as you describe for Lithium and Sodium. Another example would be that in hydrogen (Z = 1), the energy difference between the 1s and 2p orbitals is only 10.2 eV. By contrast, in fluorine (Z = 9), the energy difference between the 1s and 2p orbitals is 52.5 eV.

Thank you very much, that makes sense!

I would like to ask one more question: Does energy difference between different electron shells increase with atomic number in general? (for example energy differences between second and third shell will be higher for elements with higher atomic number)?


text:
Stability comparison between Acetylene/Ethyne (C2H2) and Nitrogen Gas (N2)
N≡N is more stable than H2N—NH2 (hydrazine)
But
HC≡CH is less stable than H3C—CH3
Why is it so? Even though the size of the corresponding compounds and hybridization is the same?
(Usually ethane is reasoned to be more stable than ethyne as : pi bonds are less stable and weaker than Sigma bonds. So hydrogenation inrpoves stability of the hydrocarbon.
But this is the opposite in case of hydrazine... Any explanations? (Perhaps the difference in bond overlap of N—H, N—N & C—H, C—C bonds?))
Why are the two cases the opposite of each other, regardless of the similarities in structures?

Stable with respect to what?

All I mean is, why is N2 more stable that hydrazine, whereas C2H2 is less stable than C2H6

If you say "whereas C2H2 is less stable than C2H4" you are almost comparing like with like and talking about stability with respect to hydrogenation. Is this what you mean?

Yes! N2 and C2H2 have similar structures. N2H4 and C2H6 have similar structures. Yet the corresponding pairs (N2, N2H4 & C2H2, C2H4) have different relative stabilities... Pretty much the opposite. Why so!?

Consider bond angles, and number of electrons involved. https://socratic.org/questions/568dc3297c014929be837991 and https://courses.lumenlearning.com/suny-mcc-organicchemistry/chapter/hybridization-structure-of-acetylene/, for example. Moral: "Like, don't get so bent outa shape and go off an' explode."

@DrMoishePippik yes! exactly my point. Both N2 and C2H2 have a linear geometry yet N2 is stable (way more than hydrazene), whereas C2H2 isn't as stable as its alkane counterpart. Why this difference!?

It's more subtle that it appears to be. An important factor is weaking of single bonds from C-C to F-F due to repulsion of electron pairs, but

@Maddy You are on the track of bond dissociation energies $\ce{N#N}$ vs. $\ce{N-N}$, and of $\ce{C#C}$ vs $\ce{C-C}$, and not stability (or reverse: enthalpy of formation) of e.g., acetylene vs ethane -- aren't you?


text:
D-d splitting in transition metal ions
Cu+2 ion has total of 9 electrons in its 3d orbital. When it undergoes d-d splitting an electronic transition can take place between t2 and e as in {Cu(CN)4}-2 complex  because of the presence of one unpaired electron and it will contribute to its colour of the complex. Ti+3 has also only one unpaired electron in its d orbital so it can also undergo transition when d-d splitting occurs.
My question is that why would Ti+3 undergo d-d splitting in the first place when it has only one electron in only one of its degenerate d orbital. I mean d-d splitting occurs because of the repulsion between electrons of the approaching ligand and electrons in the d orbital and here only one of the d orbitals has one electron other degenerate d orbitals are empty so why would d-d splitting occur in the first place??
I will be very thankful if someone answers this.

Is the Ti(III) in the gas phase? If not, what are the solvent/ligand/counterion?

With only one $d$ orbital occupied by an electron in an ocathedral Ti(III) complex the remaining $d$ orbitals are virtual states only, so to speak of splitting between them is not really proper. But we can say that because of the crystal field or ligand field effect there is some distinguishing of $d$ orbitals into which the electron may be placed. We can tell the $t_{2g}$ states from the $e_g$ states by their different energy levels; when the electron is in a $t_{2g}$ state the complex is more stable than would be predicted from a model based on spherically symmetric charge or electron distributions.


text:
Volume of gas mixture
I have inlet to a reactor formed by equimolar CH4 and NH3, I want to find the volume of this gas mixture.
First I wanted to calculate the sum of individual volumetric flow rates from V = m*rho. However, I could not find the rho values at 1 atm and 1000C for mentioned gases. My first question is that is it okay to continue with this conditions? I have found them from reliable sites, however, according to density-temperature charts, the density of these gases approach to 0 at these temperatures. Is it problem for me?
My second question is that can I find total volumetric flow rate from ideal gas law as follows?
P_total = Pa + Pb = (n_a + n_b)RT/V         ->      V = P_total/((n_a + n_b)RT)

Assuming ideal behavior, the gas density is $\rho = \dfrac {pM}{RT}$

I have inlet to a reactor formed by equimolar CH4 and NH3, I want to find the volume of this gas mixture.

In flow processes like this, it has zero value to know the volume of a mixture of gases at the entrance of any equipment. What has value is the volumetric flow rate $\dot{V}$, as you then said, which has units of $\pu{m^3 s^-1}$.

First I wanted to calculate the sum of individual volumetric flow rates from V = m*rho. However, I could not find the rho values at 1 atm and 1000C for mentioned gases. My first question is that is it okay to continue with this conditions?

When you have more than one component, you calculate the volumetric flow rate (as one), not the individual ones. Matter in that stream forms a homogeneous gas phase, and as such, unique physical properties characterise it, for instance the density $\rho$. You may imagine that if you have a pipe in which $10$ different substance travel, it will be impossible to measure the individual volumes that each one occupy.
You can calculate the volumetric flow rate as follows
$$ \dot{V} = vS =  \frac{\dot{n}}{\rho} \tag{1} $$
If you have the velocity $v$ and the cross sectional area $S$ at the reactor inlet, use the first equality. I suspect that you don't have those, so you will need to use the second equality where $\dot{n}$ is the molar flow rate in $\pu{mol s^-1}$ and $\rho$ is the molar density and $\pu{mol m^-3}$.
Since you know the conditions at the inlet you just apply an equation of state and find $\color{blue}{\rho}$
\begin{align}
  p &= f(\rho,T,y_\ce{CH4},y_\ce{NH3}) \\
  \pu{1 atm} &= f(\color{blue}{\rho},\pu{1000 °C}, 0.5, 0.5) \tag{2}
\end{align}
where the unknown variable is the density in blue. Once you have calculated, you can go back to Eq. (1) and calculate $\dot{V}$. As @Poutnik stated in the comment, just go for the ideal gas equation of state. This will be an excellent estimation, since the pressure is almost standard and the temperature is very high.

Both methane and ammonia, and mixtures of the two closely obey the ideal gas law at 1000 C and 1 atm.  The mean molecular weight for an equili-molar mixture of these gases is $$M=(16+31)/2=23.5\ gm$$   The mass density of the mixture is $$\rho=\frac{PM}{RT}$$ where P is the total pressure.  If m is the mass flow rate, then the volume flow rate is $$\dot{V}=m/\rho$$


text:
AC voltage drift
I am applying AC current to a capacitive electrode and recording the change in voltage over time. I have observed a voltage drift that does not follow any consistent pattern. Sometimes, the drift is upwards, other times it is downwards, and at times it alternates between upwards and downwards. My experimental setup involves a capacitive electrode immersed in phosphate-buffered saline, with an AC amplitude of 100µA applied. I can confirm that the electrodes are clean before the start of each experiment. There is minimal or no mechanical vibration. The electrode surface appears intact, and the solution does not seem contaminated. Additionally, there is no visible formation of bubbles. I have attached a picture for reference. Can someone please help me explain what is going on?

1/ Verify if there is any voltage drift without applied AC. 2/ Verify if AC has DC component big enough to cause the drift.

Thanks for your comment. So there is no applied DC component. In other words, the DC voltage has been set to 0V.

I mean residual DC component. Zero is zero in math, but seldom in physics.

Clearly, from the images and data, the amplitude of the alternating current (AC) is not varying, but the direct current (DC) voltage offset is. Since you state the electrodes are capacitively coupled, they could only transmit AC, not DC.
Therefore, the DC drift you observed is in the amplifier following the electrodes.

Since you're measuring AC, then the output of the amplifier should also be capacitively coupled, removing that DC offset.
A well-designed AC amplifier has DC negative feedback to increase stability. Can that be improved?
High-impedance instrumentation amplifiers can pick up currents electrostatically. Just walking past the leads can cause DC (actually, very low frequency AC) fluctuations. Shield (earth) the apparatus.
A well-designed amplifier has temperature compensation. Can that be improved?
An amplifier can be put in a temperature-controlled oven, keeping it at a stable temperature, a few degrees above ambient.


text:
Is there a name for polymer structures that resemble a foldable lattice?
I'm struggling to find the right descriptors for this, but it would look like this

I've been doing some layperson reading up on stretchy materials, and I know a lot of them work by the polymer chains unraveling (for lack of a better term), but I wondered if any such polymer could be arranged more like the pictured lattice?

It would have some rotaxanes connecting linear chains? I doubt something like that was made. In principle, it's possible, but in practice, likely pointless.

"stretchy" materials are usually 3D networks, usually not regular as you show, but with a wide distribution of mesh sizes. By swelling in what would be a good solvent for the given polymer without the network links, you can extend the chains of each mesh.

@Mithoron I agree it's likely pointless, but is there a general name for this sort of lattice structure? It's nothing like this, but layered graphene sheets at angles seem to be called a superlattice... Is there an equivalent term for the overall structure here?

@Karl yeah I imagine if it ever existed, it would be in solution, in the same way that rubber is often modeled as polymer chains in 'solution' only interactive via van der Waals forces? I'm not sure what you're saying in your second sentence... specifically 'swelling' and 'chains of each mesh'...?

If this was what I mentioned, and your post is specific enough to be sure, you could call it a mechanically interlocked molecular architecture, more precisely supramolecular polymer network

https://pubs.acs.org/doi/10.1021/cr9000622

@Mithoron yeah, MIMA and the term 'Supramaolecular' both cropped up when I went looking at related articles to your roxatanes link. I also came across Foldamer and Polymer architecture which seem like helpfully related articles.

Oh, I meant your q. is not specific enough. One could draw various analogies and a single bond can rotate better than some roxatane.

@Mithoroen the the crux of my question is, is there a name for when long chains assemble into a separate macro scale lattice where this kind of hinging/pivoting/rotating in some part of the chain lets its go from the squashed folded up version to the extended version. There may not be  catch all name, but if there's a specific name for one thing like it and not all, that's still a good answer right?


text:
Photochemistry/Physicalchemistry - Fluorescence & Solvent Form
The hint from my instructor for the answer is related to Jablonski Diagram.
The scenario: using fluorometer to measure fluorescence of a compound. How would my fluorescence results differ when dissolve analyte in water vs. water + glycerol (1:1)?
Glycerol is viscous, so the analyte will have less freedom of motion. This I got it right. But the answer is using water + glycerol would icrease intensity of my fluorescence compared to just water.
I am stuck with understanding why it increases?

Freedom of species to move and recombine before releasing energy as light?

What did you search? ChatGPT  4 provides a reasonable answer. I asked "Act as an expert in fluorescence spectroscopy " as a prompt, and then wrote "If we add glycerol to an aqueous solution of a fluorescent compound, should we expect higher fluorescence or lower?" See what answer and an equations you get.

What is being favored in water is probably the internal conversion (non-radiative decay), therefore, when going to a less polar mixture or a non-polar solvent, this pathway is less favored. Therefore, although fluorescence is not directly favored, as these two are competitive processes, the fluorescence quantum yield increases (hence its intensity as well).
Depending on what your fluorophore is, its chemical structure, polarity and the charge distribution in the excited state; different processes can occur. It is easier to rationalize it between what happens between a polar solvent and a non-polar solvent.
Polar solvents, such as water, have a high capacity to interact with polar molecules, such as fluorophores. These interactions can dissipate the energy of the excited state of the fluorophore through nonradiative mechanisms such as collisional deactivation.
It also influences what the charge distribution of your flurophore is in the excited state. In polar solvents, the solvent molecules rapidly reorient around the fluorophore in their excited state. This reorientation can generate a fluctuating electric field that perturbs the excited state of the fluorophore and facilitates internal conversion.
Additionally, if your fluorophore is very low polar, interaction with the polar solvent can increase the ground state energy of the fluorophore, reducing the energy difference between the excited state and the ground state. This lower energy difference facilitates internal deactivation by mechanisms such as internal conversion.
Since these processes are very fast, I do not think that the viscosity of the solvent plays a relevant role. Still, this parameter could be influencing the nonradiative decay constant of the solvent where the effectiveness of the collisions of the solvent and the excited state of the fluorophore are crucial.

It really is a type of trick question because the answer depends on what the fluorescing molecule is, and whether it has high/low fluorescence yield in  water/ organic solvent. Some aromatic sulphonates (e.g.ANS) have low yield in water, high in organic solvent, many other compounds hardly change yield at all with solvent. The viscosity really does not come into it unless for special cases of triphenylmethanes (malachite green for example). Glycerol it turns out is microscopically not as viscous as its bulk viscosity would suggest. A small amount of water decreases glycerol's viscosity very greatly from that in its pure state.


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Best representation of 1310384-76-9 / 1104637-53-7, a molecule with a coordination bond between nitrogen and boron
If you look up the above CAS numbers, you will sometimes find this structure:

which, I think correctly, our chemistry validation software tags as 'bad valence'.
In other websites you will find the structure without any bond between N and B:
https://www.chemspider.com/Chemical-Structure.22439675.html?rid=0012f539-17bd-4c38-b4eb-410b3a14bd7a

or some with fancy 'dative' bonds:

or some with charges on B and N:

What representation, if any of the above, or some other, is the 'recommended' one for this kind of compound?

out of curiosity, what is "our chemistry validation software"?

In this specific case, Biovia's/3DS' Pipeline Pilot. But even ChemDraw will tag B and N as problematic if I don't put the charges on.

On a side note, I would really like to know what the downvoters had to object to my question. It is based on a real life case; I am a professional cheminformatician who is asking a group of people with chemistry knowledge for advice on structural representation standards. If anyone has got problems with that, please come forward and justify your negative reaction. I've always found absolutely infuriating this vile, cowardly, completely moronic downvoting people indulge in, behind the anonymity that's unfortunately still offered by StackExchange. Either contribute or be gone already(!)

These are so-called N-methyl-iminodiacetic acid (MIDA) boronates. They were first prepared in 1986 (ref. 1) and started becoming popular after 2007 due to their use as protected boron functionalities. (ref. 2)
There is ample evidence that the B-N bond exists and is very strong, with a typical bond energy of >120 kJ/mol. Many crystals of MIDA boronates have been obtained, directly showing short B···N distances of around 1.6 Å, much smaller than the sum of the van der Waals radii of the atoms and consistent with a covalent B-N single bond. This is true in alkyl, alkenyl, alkynyl and aryl MIDA boronates.

(Visualization of a MIDA boronate structure based on crystallographic data from ref 1. Boron atom shown in pink, nitrogen atom shown in blue.)
Furthermore, NMR spectroscopic data also indicates the presence of the B-N bond in solution, and not only in the solid state. 1H-NMR data of MIDA boronates show two magnetically inequivalent proton signals for the methylene hydrogens next to the carbonyls with a typical geminal coupling constant of 15-18 Hz, meaning they do not interconvert due to restricted motion (i.e. formation of the bicyclic cage). This remains the case even at 125 °C in solution, from which lower bounds on activation energy for B-N bond scission could be established. 11B-NMR and 10B-NMR measurements can also be performed, and the boron shifts (ca. +10 ppm for 11B, relative to the $\ce{BF3.Et2O}$ standard) are consistent with tetracoordinate boron with a negative formal charge.

(Magnetically-inequivalent methylene protons in a MIDA boronate in MeCN-d3 solution, from ref. 1)
With these data in mind, the structure without any B-N bond is outright incorrect. The structure with a dative bond is also technically incorrect, because dative bonds are a deprecated concept, as they are indistinguishable from a standard covalent bond. This leaves the first and last structures you show, and both are arguably correct, as the formal charges are implicit even if not drawn.

References:
(1): Mancilla, T.; Contreras, R.; Wrackmeyer, B. New bicyclic organylboronic esters derived from iminodiacetic acids. J. Organomet. Chem. 1986, 307 (1), 1–6 DOI: http://dx.doi.org/10.1016/0022-328X(86)80169-3
(2): Gillis, E. P.; Burke, M. D. A Simple and Modular Strategy for Small
Molecule Synthesis: Iterative Suzuki−Miyaura Coupling of B-Protected
Haloboronic Acid Building Blocks. J. Am. Chem. Soc. 2007, 129 (21),
6716–6717 DOI: http://dx.doi.org/10.1021/ja0716204.

Thanks! A very comprehensive and knowledgeable answer. I am just puzzled by the sentence "the formal charges are implicit even if not drawn". No chemistry drawing or validation software I have ever used professionally accepts structures where a nitrogen atom has 4 bonds and no charge on it. So if I had to choose I would at least put the charges on, not because I particularly insist on that, but because otherwise our software rejects the molecule :D

Yeah If I had to pick one correct answer then it would be with the formal charges. The software complains because it can't be sure you drew what you wanted, it needs to call the error in order to cover other situations where you actually may have incorrect bonding. In a sense, the structure with the implicit charges is "human-readable but not machine-readable".

I see... OK so I will change the representation in our system to the one still with the B-N bond, but with the required charges. Thanks again for looking into this!


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How to safely add a lithiated reagent (R-Libenzene) to another flask using the NE-1002X syringe pump?
I would like to do a murahashi coupling (lithium coupling) between 1,4 dibromo benzene and 2,6-dinaphtalene-4-tertbutyl-iodobenzene.
I am trying to copy the exact procedure from this article:
Giannerini, M., Fañanás-Mastral, M. & Feringa, B. Direct catalytic cross-coupling of organolithium compounds. Nature Chem 5, 667–672 (2013). https://doi.org/10.1038/nchem.1678
Once 1,4 dilithium benzene obtained, I would like to add it to another flask where the catalyst and the other reagents are (as described in the original protocol).
I have never used a syringe pump before but we have the NE-1002X syringe pump. Gas tight syringes do not fit in it and thus require plastic syringes. Is there a possibility that the syringe may clog during the addition? Plastic syringes are not gas tight so any air could react with the lithiated specie and cause problem.
Hence has anyone ever done a similar reaction and could explain how to proceed safely?
Are there other types of syringe pumps which allow to use gas tight syringes to remain in an air free water free environment?
Thank you!

I have only ever done these kind of reactions by hand syringe or pressure-equalised dropping funnels, but rigid temperature control of the reaction mixture is key to getting a good yield. The dilithio benzene very easily decomposes with just a few degrees of warming

If I presume you have access to a Schlenk line, an alternative approach may be a cannula transfer.
After the separate preparation of reagent(s) A in solution in flask A, a light additional pressure is used to transfer it to reagent(s) in flask B:

(with light edit, image credit to schlenklinesurvivalguide.com)
The connection between the two flasks usually is established with a transfer cannula.  In contrast to the needles on the (injection) syringes, these double tip to pierce two septa, steal inox needles are available as wide bore/bigger inner diameter, can be baked out like your glass ware, and still are somewhat flexible for a gentle elbow.  There equally is one form where the two tips are joined with flexible tube between the two; Sigma for instance distributes them as Chem-FLEX™ transfer line, more useful for bigger quantities and larger distances to bridge:

(Sigma-Aldrich's Chem-FLEX™ transfer line)
Except the transfer cannula, the setup can be immersed into a larger Dewar filled with dry ice and iPrOH, too:

(from Wikipedia article Cannula transfer).
This approach will not provide reagent solution A at $\pu{-78 ^\circ{}C}$ to enter reagent solution B, is not suitable to add this slow (and enduring) as can the setup with a syringe pump.  With only a short tube connecting the two tips, the reagent however remains under inert conditions, likely much cooler than stored in a syringe mounted on a syringe pump, and relieves you from a search of a needle with fitting Luer lock to secure the joint.  If the technique is new to you, train the transfer a couple of times with the bleeding valve at the Schlenk line at room temperature with a bit of EtOAc, or THF before engaging the real reaction.
At a larger scale:

(image credit to Xu et al.)

An advanced version of this would be to set up flow chemistry, a topic for which for instance the group by Steven Ley (Cambridge UK) is known for:

(image credit Ley group)
To design this, one needs to know the underlying kinetic data; then, chemical engineering steps in e.g., to estimate a useful time of residence in these tube reactors.  But once installed, up and running, the steady state of the continuous flow allows some operations (too) difficult/dangerous to apply with round bottom flasks, including lithiation reactions.
The author of schlenklinesurvivalguide.com equally compiled his experiences in a paper: Borys, A. M. An Illustrated Guide to Schlenk Line Techniques. Organometallics 2023, 42, 182–196. https://doi.org/10.1021/acs.organomet.2c00535.
Xu, H.-C.; Chowdhury, S.; Ellman, J. A. Asymmetric Synthesis of Amines Using Tert-Butanesulfinamide. Nat. Protoc. 2013, 8, 2271–2280. https://doi.org/10.1038/nprot.2013.134 (author's copy on Researchgate).
Brégent, T.; Ivanova, M. V.; Poisson, T.; Jubault, P.; Legros, J. Continuous‐Flow Divergent Lithiation of 2,3‐Dihalopyridines: Deprotolithiation versus Halogen Dance. Chem. Eur. J. 2022, 28, e202202286. https://doi.org/10.1002/chem.202202286 (open access).
Power, M.; Alcock, E.; McGlacken, G. P. Organolithium Bases in Flow Chemistry: A Review. Org. Process Res. Dev. 2020, 24, 1814–1838. https://doi.org/10.1021/acs.oprd.0c00090 (author's copy here).

Thanks a lot for this extremely detailed and useful explanation. I am familiar with canula techniques but have never thought it could be suitable to add reagents at a controlled rate. I will try this! Thanks a lot! The details you provided will definitely help a lot.

@TheRedManJolanBonelli I moved a comment about flow chemistry as an advanced technique (compared to the transfer cannula) into the answer, because this can be appealing and worth the investment.  It depends ...

Since I do organic synthesis in academia at a research level in the material science field (no pure organic chemist), the cannula transfer method is more appropriate (I have everything I need and already am use to such protocols) I will definitely read up on the flow chemistry set ups as I am very unfamiliar with it. Thanks a lot for the extra information.


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What is the significance of PV in Enthalpy (H=U+PV)? Are we adding work twice in the equation?
I have 3 questions:
Enthalpy is defined as:
H = U + PV

What exactly does PV signify?

Also from the First Law of Thermodynamics
∆U = q + w
w here means work (done by, say, the system).
So,
∆H = q + w + ∆(PV)
2. In the above equation are we adding work twice?
I asked chatGPT about it, it said we are not.
I need a more deeper explanation of what the distinction between PV and w is.
There seems to be a distinction between the PV work in
w = -P∆V (if PV work is being done ex: gas expansion or compression) and
the PV term in
H = U + PV

What is this distinction?
Could someone please explain with examples.

U is internal energy of an object. H includes squeezing by pressure - atmospheric in particular. BTW this was likely asked here like half a dozen times :/

Not twice, it cancels out if the pressure is the same before and after (and you keep the sign conventions straight).

Your equations should read $$\Delta U=q-\int{P_{ext}dV}$$ and $$\Delta H==q-\int{P_{ext}dV}+\Delta PV$$If $P_{ext}=P=const, $, these equations reduces to $$\Delta U=q-P\Delta V$$and $$\Delta H=q$$


text:
I analyzed samples for arsenic with ICP-MS, my calibration standards are off. Any suggestions?
I used a multi-element calibration standard (10 ppm, with As,Fe,Mg etc.) from a vendor. I then diluted this down to get calibration standards of 0, 1, 2, 5, 10, 20, and 100 ppb. I analyzed these standards along with my samples with ICP-MS.
My intensities for Fe, Ca, As, Mg aren't linear for my standards, and arsenic has the same intensities (0 or 7) for my standards. How is this possible? I attached a picture of my intensities. Also, I mostly care about arsenic.
If I made a mistake when preparing my standards would there not be at least an increase in As and Fe, Ca, and Mg, since the standard contains all elements.
Let me know if anyone has any suggestions.

Are your standards aqueous solutions ? How did you prepare your dilutions ? With pipettes ? Which volume did you mix with which volume water ? Were these dilutions made in glass bottles ? Which volume ?

Can you make a clean table so that it is readible? Also plot the calibration curve and show the concentration behavior, "not linear" does not tell the story.

Thank you for your responses. Here is the table with the number of counts per second for the standards

@Maurice the standards are solutions and I used plastic tubes.


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What do the arrows mean in the Structural Formula of Oxaliplatin?
What do the arrows mean in the Structural Formula of Oxaliplatin? I haven't seen these and couldn't find anything explaining them.

The free diamine has a nonbonding pair on each nitrogen atom; the arrows indicate that these pairs are incorporated into dative bonds to form the complex.
Thus the complexed diamine has two positive formal charges with the compensating negative formal charges on the platinum. Note, however, that the oxidation state of the platinum, which is calculated assuming ionic rather than covalent bonding, is +2 (which is commonplace in platinum complexes).

Why would the nitrogens even react with the platinum? Isn't their valence full with the C and 2 H's, via the octet rule?

@imrobert The nitrogen atoms in the amine carry a non-bonded pair of electrons; hence, they are Lewis bases.  The platinum(II) cation on the other hand has a gap, "is missing" electrons to complete its outer valence shell; hence, it is a Lewis acid.  In consequence, the Lewis base donates electrons the Lewis acid accepts.  (There is some share of electron density between the two to establish a chemical bond though.)


text:
How to name LiN(CF2SO3)2?
I found this compound in the list of inorganic lithium salts from this article on ScienceDirect.
It is said to be of the sulfonate group. Let's focus on the anion alone.
I'm not sure if it can be bis(difluoromethanesulfonyl)imide because there is already a compound named bis(trifluoromethanesulfonyl)imide / bistriflimide ($\ce{LiN(CF3SO2)2}$). The structure is given on Wikipedia.
I've also seen other compounds like $\ce{LiCF3SO3}$ (lithium trifluoromethanesulfonate / lithium triflate) and $\ce{LiC(SO2CF3)3}$ (lithium tris(trifluoromethanesulfonyl)methide / lithium triflide), but nothing with $\ce{CF2}$.
The sulfonate ions are of the form R−S(=O)2−O−, and the sulfonyl group is of the form R−S(=O)2−R.
The only ways that make sense to me are -CF2-(SO2-O)-(O-SO2)-CF2- and -SO3-CF2-CF2-SO3-, both of which seem to form cyclic amides (the two ends connected to N). But I'm not sure if such a molecule will be valid or how to name them.

Edit: and one more: CF2=(S=O)-O-N-O-(S=O)=CF2. But this seems even more weird.

Edit 2: I would say, since $\ce{SO3^{2-}}$ is sulfonate, and $\ce{SO2}^2-$ is sulfoxyl, contrary to the Wikipedia page, $\ce{LiN(SO2CF3)3}$ would be lithium tris(trifluoromethanesulfoxyl)imide as opposed to lithium tris(trifluoromethanesulfonyl)imide.
That would make $\ce{LiN(CF3SO3)3}$ lithium tris(trifluoromethanesulfonyl)imide. When I Google for it, different sources mention lithium tris(trifluoromethanesulfonyl)imide as $\ce{LiN(CF3SO3)3}$ or $\ce{LiN(CF3SO2)3}$, but I don't see any other names. This is probably due to the short name lithium bistriflimide / lithium triflimide (Li-TFSI).
Edit 2.1: I forgot that sulfonyl group  was of the form R-SO2-R'. So maybe Lithium tris(trifluoromethanesulfonyl)imide is correct.

What would be the name of this compound?

Though not an answer https://en.wikipedia.org/wiki/Bistriflimide#Naming may be of interest

Let us continue this discussion in chat.

From the answer by @NicolauSakerNeto to my other related question (Is LiN(CF3SO3)2 is valid, being similar to Lithium Bistriflimide (LiN(CF3SO2)2)?), it seems that the compound is not as popular is it seems from the papers.
He mentioned that the -O-N-O- bridge appears unstable (although I'm unsure why), and the compound would re-arrange itself into something else, which would make sense for $\ce{LiN(CF3SO2)2}$ to form instead.
He suggested that I check the CAS database, and in it, there are only two compounds with the $\ce{CF3SO3}$ backbone and one reference from an obscure patent, while there were more than 14000 compounds with the $\ce{CF3SO2}$ backbone and over 40000 references.
But checking the CAS database is impractically expensive for anyone who does not have a commercial or academic license, so as it stands, we'll just have to rely one someone else with access to the database to check it for us.

Update:
I found some compounds with a related structure ($\ce{N(CF3SO3)2}$) by using ChemSpider, with associated CAS numbers, but @NicolauSakerNeto still mentioned that those compounds are suspicious.
But in case the compound was real, it would be named N,N-Bis(trifluoromethylsulfonyloxy)amide. Again, this compound may not be a valid one.

You know, by mentioning you should be careful with deleting, I didn't mean you should undelete it? Well, making this extended comment, that doesn't answer it,also wasn't a good idea :(

@Mithoron I read about the guidelines and it said deletes count towards mistakes and you should focus on fixing the question. So I thought it'll be best to provide the answer I was expecting to my doubt.


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Solubility of alkali and alkaline earth metal carbonates
The solubility of alkali metal carbonates increase down the group, while those of alkaline earth metals decrease down the group.
We can explain the decrease in solubility of alkaline earth metal carbonates by stating that their lattice enthalpies remain somewhat the same due to the larger size of the carbonate anion, and the hydration enthalpies of the metals keep decreasing down the group.
If we were to apply the same principle to the carbonates of alkali metals, the order would be opposite to what is actually observed. Why is it that the solubility of alkali metal carbonates increase down the group ? What makes them show a different trend than the alkaline earth metal carbonates ?


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Cyclohexane replacement in Food Chemical Analysis
We have to use cyclohexane in the laboratory for the chemical analysis of olive oil in the UV spectrometry. But it's highly toxic for respiration.
Can anyone suggest a chemical to replace cyclohexane but which is safer to use the same in the UV spectrometer?

Cyclohexane isn't "highly toxic". It's just a cycloalkane, hardly different from fuel you got in a car.

Most of solvents are more toxic than non-aromatic hydrocarbons.

Cyclohexane (Wikipedia reports a boiling point of $\pu{80.74 ^\circ{}C}$ presumably at ambient pressure) is not this much toxic that a single accidental inhale will kill you -- but did you consider to i) close the optical cell with a lid (if lost, get in touch with a manufacturer), and ii) do you work in a well aerated lab?

(image credit fireflysci.com)
Though more often seen in labs working with dusty samples, there are dust extractors one can join to the exhaust pipes of a lab; these «umbrellas» can be adjusted in height and position over other equipment without obstruction of the lab bench (not a replacement for fume hood):

(image credit to labtechsupplyco.com)
One may think about n-heptane, with a boiling point reported with $\pu{98.38 ^\circ{}C}$, similar to the one of water.  However, each substitution of the solvent can open complications.  For one, the solubility of the analyte(s) may change, and the position of the absorption bands (keyword solvatochromism).  At what level are these changes chemically significant?  Only the collection of new reference data and calibration curves can answer this.
Chemistry aside, if the analysis is required by local law, the intended swap can constitute leaving the official protocol your lab got the accreditation for, and invalidate the results of the analysis legally.  But perhaps your customers do agree that you use a different protocol recognized by a body like FDA, ISO, ASTM, etc.

Most organic solvents are inhalation hazards; that is no reason to be paranoid about using them carefully.  Cyclohexane is low in toxicity. Bulk use of solvents should be in a fume hood or in a sealed system with a condenser. Samples for uv-vis analysis should be in well stoppered cuvets to prevent evaporation. Cyclohexane seems to be useful as the solvent to measure olive oil pigments in the visible and near uv. It can be obtained pure the only contaminant a trace of benzene that absorbs near 270nm. Cyclohexane must dissolve all the common components of olive oil and is volatile enough to be removed by careful distillation under slight vacuum. A substitute for work further in the uv where benzene might interfere would be n-hexane.


text:
How many times does substitution happen here?
(This question is from a dubious source)

The reaction taking place here is Friedel-Crafts acylation of benzene with 1-chloro 2,2-dimethyl propanone (pivaloyl chloride?). To me, the options seem most peculiar. When the $\ce{C} - \ce{Cl}$ is broken, it gives rise to a carbocation at the carbon of $\ce{C}=\ce{O}$ bond.
According to my teacher, $\ce{C+}=\ce{O}$ now leaves with the electrons of the adjacent $\ce{C}-\ce{C}$ bond, giving rise to a stable tertiary butyl carbocation. This leads us to $\ce{PhCMe3}$.
Edit 2: this is the same reaction: Unusual Friedel–Crafts alkylation with pivaloyl chloride
Considering that the t-butyl group is para-directing, the options still don't seem right to me. If this conversion to a t-butyl carbocation happens once, can it not happen again? Would we simply not get two t-butyl groups para to each other?
(I still doubt multiple substitution is even possible)
Edit 3: as of 24/2/2024 this question has been confirmed to be of poor quality. See reasons in comments.

According to the person who gave me this question, the answer is B.

tBu group is similar to Me and electron-donating and so activating and p-directing

See the answer to this SE question  https://chemistry.stackexchange.com/questions/38454/unusual-friedel-crafts-alkylation-with-pivaloyl-chloride

@Waylander thanks, that's the same reaction - but it concludes with only tert-butyl benzene.

I strongly suspect that you would get at least some of the 1,4-di-tert-butyl benzene in the reaction mixture, possibly the major component. The acylium species is not going to stop being a source of tBu+ and the t-Bu-benzene is more activated than benzene itself.

All right, my teacher confirms this is a poor question. The alternatives listed as the possible products are all incredibly minor.

You'd get pretty much zero C, little D, but if you got B, then A would also be present and I second what Waylander said.


text:
Is 304 stainless steel an appropriate choice for making a tin/lead solder pot?
Are 304 stainless steel plates suitable for making a tin/lead melting pot operating at 300 °C or 572 °F?
My concern is that the liquid alloy could form a kind of amalgam on the surface of the steel, therefore not only slowly corroding it, but also contaminating the solder alloy with nickel and chromium from the stainless steel.

Note, almalgam is a term to address alloys of mercury.  But in your question, mercury does not occur.

TubingChina.com states:

Resistance to molten lead (m.p. 327C)
Lead, in the presence of oxygen, is more aggressive than lead covered
with a charcoal layer. At 400C some attack to 1.4301 (304) type can be
expected. The 1.4401(316) type and higher alloyed austenitic should be
resistant. If temperature are as high as 900C then a charcoal
oxidation inhibiting layer is essential if severe corrosion is to be
avoided. Any antimony in the lead can increase the risk of corrosion.
Resistance to molten tin (m.p. 232C)
Molten tin should not attack austenitic stainless steel below 400C. At
400C some attack can be expected, which becomes severe at temperature
of 500C and above.

In summary, at 300°C, rather than 400°C as in the reference above, I'd expect some slow corrosion to type 304 stainless steel from a $\ce{Pb/Sn}$ solder. This raises two questions:

How will the solder be used? In critical aerospace use, for example, with lead-tin solders, extreme care was taken to ensure that the alloy contained no contamination of other materials dissolved from equipment (among other things, it helped prevent tin dendrite growth). For use as a solder pot for commercial lamps, that would not be critical.
How thick will the container wall be, and for how long will it be in service? For a few weeks use, with thick metal, there likely would not be an issue. For a year, be prepared for a disaster, when the solder pours through the corroded vessel wall.

The reference also suggests floating charcoal on the solder surface to slow oxidation of the vessel (which should also make the solder itself last longer).
Consider using austenitic 316 stainless steel, which that reference states is more resistant to both molten tin and lead.
Also consider coating the solder pot, as in this study using ceramics. Of course, any coating must be adherent and survive an occasional heating/cooling cycle of the pot. You'd need to do some research on that.


text:
What is the oxidation state of the two tin bonds in the below structure?

I understand that typically, ethylene as a ligand has a neutral charge and would not contribute to the oxidation state of the transition metal bound to it. However, I am seeing conflicting information as I try to determine the oxidation state of each of the tin centers. The Ar group is anionic and the tin would thus be at least Sn(I). However, I am seeing claims that ethylene as a bridging ligand acts as an anionic ligand instead of a neutral ligand. Could anyone help/teach me how I should go about determining the oxidation states of each of the tin centers?

The language here is confusing. Oxidation state is a concept to aid our understanding of chemistry, not some fundamental property of nature. A tin center doesn't walk around with an oxidation state, so there is no meaning in what you can claim it to be.
You should split this system in half for symmetry and look at the ligands. There should be 3 anionic ligands.


text:
Can Sodium atom (Na not Na+) be considered a free radical?
By definition "Free radical is a chemical species that has a single unpaired electron in the outermost orbit". Sodium atom also has a unpaired electron in outermost shell and it is also highly reactive.
So, can it be considered a free radical and thus claiming that it can cause cell injury by oxidative damage?

Sodium almost always exists as Na+. The free metal does not exist in nature. wikipedia

Sodium can reduce things, not oxidise, and there's absolutely no atomic sodium in any water solution.

Some radicals are strong oxidants, some strong reductants and some are not found in water solutions as there are no processes that would create them and keep them.

@zxen-xi, as you say, on Earth, sodium is almost always ionized... but "in nature" might be a bit to broad... after all, people are part of nature, and we do make metallic sodium, and it's relatively inexpensive, ~US$2/kg at https://www.made-in-china.com/products-search/hot-china-products/Wholesale_Pure_Sodium_Metal.html

But the context is biological matrix, where no atomic sodium occurs.

I'm not sure we can really consider metallic sodium in a bulk metal to be a free radical...

Na atoms can be considered a radical but only in a context where they are stable. Possible situations are the gas phase, mercury amalgams, some metallic solutions, electrode reactions that do not involve water, possibly in liquid ammonia solution. Sodium atoms play no role in body biochemistry because it is waterbased and potentials are too low to reduce sodium ions to atoms.


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Is it possible to make thermite that detonates?
Why does thermite burn pretty slowly? Can it burn much faster if the components were ground to much smaller grain sizes? Can it be made to actually detonate--that is, the entire pile turning into liquid metal at the speed of sound, not necessarily exploding?
I suppose that it might require something like dissolving both the aluminum and iron oxide in something, then evaporating the solvent to achieve a properly fine mixture. Would that work? If not, why?

"Solid state explosives are very rare." - What did you mean by that? TNT, ANFO, dynamite are solid.

Solid state explosives making only solid state products - that's the problem with thermite. There's no gas produced.

Dissolving aluminium and iron oxide means reactions, not true dissolution. You would not get back by evaporation.

There are two types of explosive: those that detonate and those that deflagrate (to use technical terms with a specific meaning). I suspect the question would accept either definition though it uses the word "detonate".
The difference between the two terms is the speed of propagation of the reaction in the explosive material: in detonation the reaction travels faster than sound; in deflagration it travels more slowly. Most would say both "explode".
TNT detonates. Guncotton deflagrates. TNT doesn't explode easily and needs to be triggered by a small very rapid detonation of something like a metal fulminate. In TNT the pressure wave from the initial trigger is sufficient to trigger an explosion in the bulk TNT and this propagates through the material much faster than sound. Guncotton is triggered in a similar way but the reaction propagation is slower than sound (which is valuable if you want a "gentle" bang that pushes a bullet or shell from the barrel of a weapon rather than bursting the barrel).
Those mechanisms are relevant to the question about thermite. The reaction in thermite is very hard to initiate. It requires a great deal of heat not pressure. This simply cannot propagate as fast as a pressure wave, so thermite cannot be turned into an explosive without some way to raise the temperature of the entire mixture to perhaps 2,000 °C very rapidly.
So thermite cannot "explode" with detonation though it might be termed deflagration though such a slow one it would not normally be called an explosion at all.

To be more specific, it is meant faster than speed of sound within the solid explosive.

Faster than sound? That's quite a shock! ;-) BTW, there's a schlieren video of shock waves from canned air and compressed air at https://www.youtube.com/watch?v=DfYlLns0els

Heat moves in three general ways:

Conduction, mediated by phonons, lattice vibrations, that, in a crystal (e.g., diamond or graphene), or in a superfluid (He II), propagates at the speed of sound. However, thermite is a mixture, not crystalline, and phonons scatter, making heat travel far slower -- as in pitch.

Convection, where there is movement of material. When a brisant explosive detonates, material is ejected faster than the speed of sound, forming a shock-wave. However, there is no violent ejection of nitrogen, as in the detonation of TNT or C-4, in placid (if a bit warm) thermite. That displacement reaction offers no great volume change.

Radiation, where photons carry energy. Though thermite emits a great many photons (wear welders goggles while watching), the photons don't propagate inside the mixture, which is opaque.

In brief, then, the answer is "No, thermite cannot detonate."
Footnote
In a transparent medium, it might be possible that a detonation could proceed at the speed of light! Perhaps someone can try this: fill two clear glass tubes, separated by a few cm, with nitroglycerin, and see if a detonation in one propagates to the second at the speed of light, initiated by photons.
If someone plans to do this, please let me know, so I can distance myself strategically.

While lattice vibrations might move at the speed of sound, heat clearly does not. If it did you would burn your hand every immediately on putting a metal poker into a hot fire.

@matt_black, the speed of sound is the limit, but crystal defects prevent transfer at that speed. However, in crystalline carbon (diamond and graphene), and in liquid helium, there is little scattering and heat can propagate that fast.


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How to measure heat transfer and heat dissipation in a kitchen?
I am a chemistry beginner just starting to coming to grips with stoves and Bunsen burners.
I would like to know, what kind of instrument can I use to measure the amount of heat transferred from a kitchen stove to a pot, in, units of heat per second (what are heat units?), and, does it depend on the height of the pot above the stove (space in between), and, heat dissipation in the pot stand metal and in the pot metal (how would I measure this, too, and what units would I use to measure this, for example to measure heat dissipation)?

[OP] I would like to know, what kind of instrument can I use to measure the amount of heat transferred from a kitchen stove to a pot [...]

A thermometer placed in the pot filled with water. Ideally, you would stir so that the temperature is almost uniform. You would need to know the heat capacity of water at the temperature ranges you encounter, and how much water is in the pot. You would also have to do a separate experiment to check the heat capacity of the pot.

[OP...] in, units of heat per second (what are heat units?),

Heat is transfer of thermal energy, so it has the same units as energy (e.g. Joule).

[OP...] and, does it depend on the height of the pot above the stove (space in between),

Yes. There is a German expression "einen Zahn zulegen" (roughly to add a tooth), which means to speed things up. Pots were suspended over open fire with a ratchet mechanism, and you would lower them to make things cook faster (or burn, if you overdo it).

Source: Von Axel Ropte, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17205393

[OP...] and, hear dissipation in the pot stand metal she in the pot metal (how would I measure this, too, and what units would I use to measure this (for example, to measure heat dissipation))?

This is a bit too garbled to understand.