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Melting point of Scandium group elements
As I am learning about elements physical properties, i notice that the melting points of Sc, Y, La, Lu decreases down the group. I suppose the increase of atomic mass would result in better Van der Waals interaction and therefore bigger melting point. Any thoughts?

There's metallic bonding in there, not vdW, and good luck understanding it.

Scandium is hcp at room temperature, bcc at the melt (1608K for hcp->bcc, 1814K is the melt). Yttrium is similar, but hcp->bcc is at 1751K and bcc->melt at 1795. Lanthanum starts as dhcp, goes dhcp->fcc at 550K, fcc->bcc at 1134K, and bcc->melt at 1193K. Lutetium stays hcp all the way to the melt at 1936K. Clearly lots of stuff is going on (all those allotropes, etc.). Complex metallic bonding is not really amenable to simple intuition.

See this question and links therein: https://chemistry.stackexchange.com/questions/171198/why-do-mn-and-tc-have-lower-melting-points-with-respect-to-their-immediate-neigh/171225

I will restrict my reasoning to the path Sc $\rightarrow$ Y $\rightarrow$ La. I have answered a similar question for the $3d$ series : Why does Cr have higher melting point. I have assumed that the melting point is related to the strength of the bond and the cohesive energy of a rectangular band of a bandwidth $W$.
This time I will assume this time that the strength of the bonds is related to the bandwidth and not directly to the electronic charge with a strength $k \propto W $, this relation is very approximate and not generally exact. Without wanting to lose my audience, I will use the translational operator $\hat{T}$ that generates the hamiltonian :
$\hat{H} = -t \sum_{i,j,\sigma} c_{j\sigma}^\dagger c_{i\sigma} + h.c$ with the condition of commutation of a weakly correlated system $[\hat{H}, \hat{T}] = 0$ so that $t \propto W  > 0 $, the hopping integral $t$ generated bandwidth, intuitively this translational symmetry is enhances by a strong attractive potential, it means that $t(\ce{Sc})>t(\ce{Y})>t(\ce{La})$, so the melting point associated  to this translational symmetry drops from the Sc to La.


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Does the term "vapor pressure" even mean anything in an open system?
I know this type of question has been addressed before, but I believe mine is slightly different and hints at a potential misunderstanding I've had for a long time.
I understand the concept of equilibrium vapor pressure, that molecules with high enough energies escape the surface of a liquid until the rate of evaporation = rate of condensation. I also understand that for a given temperature, a substance has a characteristic saturation vapor pressure. But one thing bothers me: when considering a system open to the atmosphere, does it even make sense to talk about a vapor pressure developing? Consider, for example, water vapor at 95 C. Obviously, evaporation still occurs at the surface, but since its saturation vapor pressure is less than the surrounding atmospheric pressure, can we even consider a "vapor pressure" to develop, or is this a term that holds meaning only within the context of closed systems? (I suppose, however, that it does make sense to speak of the vapor pressure in an open system once the boiling point is reached since there is quite literally a vapor pressure building up in bubbles that can push back the atmosphere...)

Umm, that's perhaps the most obvious one. Simply how much pressure something creates in a certain point and time. If system is open or not is irrelevant - it's not like pressure truly averages out either way.

How about this:  in an open system, a substance with a higher vapor pressure will evaporate faster than an substance with a lower vapor pressure.

@user123462 With higher equilibrium vapor pressure, I think OP gets this one.

In an open system like you describe, the partial pressure at the liquid surface is observed to be at the equilibrium vapor pressure.  This is typically higher than the partial pressure in the free stream of air, so there is a concentration driving force for diffusion of vapor molecules away from the liquid surface and into the air.  Usually, all the action takes place in a thin concentration boundary layer close to the surface where the partial pressure varies rapidly with spatial position from the equilibrium vapor pressure at the surface to the free stream value at the edge of the thin boundary layer.  The evaporation rate (mass transfer rate of vapor) is usually quantified by $$\phi=\frac{k}{RT}(p^*-p_{\infty})$$where $\phi$ is the water vapor mass flux (moles/cm^2), p* is the equilibrium vapor pressure at the liquid surface, $p_{\infty}$ is the partial pressure at the outer edge of the boundary layer (free stream value in air), and k (cm/sec) is the  "mass transfer coefficient."  The mass transfer coefficient is related to the diffusion coefficient of vapor molecules in air D and the boundary layer thickness $\delta$ by $$k=\frac{D}{\delta}$$There are experimental (dimensionless) correlations which have been developed to calculate the mass transfer coefficient from the air flow parameters.

Imagine the open system, but the evaporation is faster than mass transfer. Then the open system about reaches saturation.  The partial pressure of vapor is approximately equal to (saturated) vapor pressure and the pressure difference to external pressure is compensated by partial pressure of the system air.
If the mass transfer is faster than evaporation, the open system does not reach saturation and vapor partial pressure is smaller than (saturated) vapor pressure.
Still, the vapor pressure is good criteria to evaluate volatility of liquids at given temperature. Liquids with somewhat higher boiling point and smaller molar enthalpy of evaporation than water, like toluene, have at room temperature  higher vapor pressure than water. And therefore toluene is more volatile.

It sounds from the question as if you may not be taking into account the concept of partial pressure. In the example of water vapor at 95C, the relevant vapor pressure is the partial pressure, which is the pressure the water vapor would have if there were no other gases present. So it does not matter that the vapor pressure is less than the ambient atmospheric pressure, since you can treat it separately from the rest of the atmosphere.
In a well-mixed sample of ideal gases, the partial pressures can be added together to provide the total pressure. But the other gases cannot be completely ignored, since they slow the rate at which the water vapor leaves the neighborhood of the liquid surface (mass transfer). This allows there to be an approximately equilibrium vapor pressure near the surface, with a much lower pressure further away.
I apologize if this answer is telling you things you already knew, but I thought it might be helpful if you didn't.

source: Stack Exchange

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

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How to make a benzyl position more electrophilic?
I have to write a synthesis (just below) of a molecule and propose reactants and conditions :

But I have a problem with the 2nd step. Where I need to do the ether.

Apparently it's very difficult to deprotonate the H of the allylic alcohol, so I can't use NaH on it and then react it with the nitrobromobenzene.
Instead, I have to activate the electrophily of the C next to the Br and I really don't know how can I do.

My proposition is that I can reduce the bromobenzene by using the NADH and reductase so I can have an NH2 and then by delocalization I can have a very electrophilic position where the alcohol can react and I will use a base like NEt3 to deprotonate. I am not very sure about that....

Who says it is hard to deprotonate allyic alcohols? Your main problem appears to be that you have a diol and no way of distinguishing between the two -OH groups.

@Waylander thank you for your reply but it is like in the 3rd picture (that I just added)

Do you have to use the p-nitrobenzyl bromide? A better route starts with p-nitrobenzyl alcohol

Take your starting hydroxy ester (preferably methyl ester) and form a sulfonate by reaction with tosyl/mesyl chloride.
React this material with the anion of 4-nitrobenzyl alcohol (NaH/DMF) to form the ether. This is strongly favoured as the sulfonate is reactive as it is allylic.
Isolate this product then reduce the ester group with lithium borohydride in ether containing 1eq of MeOH as described here. This will selectively reduce the ester to the alcohol (leaving the aromatic nitro group untouched) which can then be reacted with the phosphonyl chloride.

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Redox titrations : Oxidation of metallic Iron by Potassium Dichromate

$\pu{0.31 g}$ of an alloy of $\ce{Fe + Cu}$ was dissolved in excess of diluted $\ce{H2SO4}$, and the solution was made up to $\pu{100 ml}$. $\pu{20 ml}$ of this solution required $\pu{3 ml}$ of $\frac{N}{10} \ce{K2Cr2O7}$ solution for the oxidation. The percentage purity (in closest value) of $\ce{Fe}$ in wire is ____.

I am approaching the problem with the following method. Let us assume the weight of $\ce{Fe}$ in the alloy to be $x$ grams. By the law of chemical equivalence, we know that the number of equivalents of $\ce{Fe}$ is equal to the number of equivalents of $\ce{K2Cr2O7}$.
To find the number of equivalents of $\ce{Fe}$ we need the corresponding chemical equation which I tried to find in vain on Google. I just want to know the oxidation state $\ce{Fe}$ would acquire. Then, I can easily answer this problem by substituting $n$ (number of electrons lost by $\ce{Fe}$) in the equivalence equation for this particular problem:
$1000n / 280 = 1/10$. From here I can easily calculate the percentage purity of $\ce{Fe}$.

Google cannot find these calculations, because such calculations are no longer taught so probably no one has webpages on this topic. They are obsolete (although some chemical industries still use it). Search normality calculations or see solved examples in your textbook which is still using normality.

You should be able to formulate the chemical equation of the reaction on your own, knowing the basics of chemistry of iron and chromium.

There is no problem in doing the mathematics. I just can't find the Reaction involved here. I will once again try to find it in my textbook. Thank you guys.

That was my point. You should not need to search for it. Hint: Cr:  +VI->+III    Fe:  0->+III

The beauty of normality calculations is that you do not need a chemical equation for this problem. Plug and chug in C1V1=C2V2. C1 is Fe conc. in normality, V1 is volume of iron sample, C2 is concentration of K2Cr2O7 in normality and V2 is the burette volume.

The last hint is that you should know how to calculate the equivalent weight of Fe2+. Search these terms in your textbook.

I have doubts about iron and copper miscibility.

Yeah I was also thinking about the oxidation of copper by iron. But in a similar problem like this where some other metals purity was to be found, they neglected the reaction. I dont know why.

Oops sorry, I have forgotten the dissolution step. Then obviously Fe: +2 -> +3.  As Cu is filtered out, Fe^3+ will not oxidize it. My miscible point was about eventual impossibility to make Fe/Cu alloy. The task may be made up. It also does mention necessary filtering undissolved Cu.

Let's reason with molar units.
Expressed in molar units, $\ce{K2Cr2O7}$ N/$10$ is $\ce{K2Cr2O7}$ M/$60$.
$3$ mL $\ce{K2Cr2O7}$ N/$10$ contains $0.003/10$ equivalent.
In molar units $0.003/10$ equivalent is $0.003/60$ mol $\ce{K2Cr2O7}$ = $0.05$ mmol $\ce{K2Cr2O7}$.
The equation of the titration becomes : $$\ce{Cr2O7^{2-} + 6 Fe^{2+} + 14 H+ -> 2 Cr^{3+} + 6 Fe^{3+} + 7 H2O}$$ Because of the coefficient $6$ in front of $\ce{Fe^{2+}}$ in the equation, $0.05$ mmol $\ce{Cr2O7^{2-}}$ has reacted with $6$ times more $\ce{Fe^{2+}}$ = $0.3$ mmol $\ce{Fe^{2+}}$. This amount of $\ce{Fe^{2+}}$ comes from the same amount of metallic Iron, i.e. $\ce{0.3}$ mmole $\ce{Fe}$, because the reaction of iron with a diluted acid is  $$\ce{Fe + 2 H+ -> Fe^{2+} + H2}$$ But the initial solution of $\ce{Fe^{2+}}$ had a volume of $100$ mL, and only $20$ mL was used for titration. It means that the initial metallic sample contained $5$ times more iron than $0.3$ mmol, which is $1.5$ mmol $\ce{Fe}$.
As $1.5$ mmol $\ce{Fe}$ weighs $1.5·56$ mg = $84$ mg, it means that the proportion of iron in the initial sample is $\frac{0.084}{0.31} = 27.1$%


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Why is the 'cis-1,3-dimethylcyclobutane' conformation of both methyl groups at the bottom more unstable than both at the top?
I'm having trouble understanding why both methyl groups on top of the ring is a more stable conformation than both at the bottom of the ring.
I found a reasoning that says the steric strain between two -CH3 groups are less when both groups are on top. (Figure (a))
Are the methyl groups closer to each other when they are both under the ring? Can this have something to do with the ring structure being a little 'twisted' or 'puckered' to minimize torsional strain?

The cyclobutane ring is ~35 degrees out of plane an conformationally flexible. Same principle apply as in 1.3-dimethylcyclohexane.


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Does real-world gas phase chemistry use "concentration reaction quotients" (K_c)?
As a theoretical chemist, my entire exposure to reaction quotients and equilibrium constants ($Q$ and $K$) is through thermodynamics ($\Delta G^\ominus = - RT \ln K_{eq}$ and so on).
So as I started teaching first-year chemistry I was very surprised to encounter the concept of expressing gas activities in molarity and a "concentration reaction quotient" $K_c$ for gas reactions, such as

For the reaction $\ce{N2(g) + 3H2(g) <=> 2NH3(g)}$, find $Q$ if $\ce{[N2(g)]}$ = 0.04 M and $\ce{[H2(g)]}$ = 0.09 M. If $K$ = 0.040, in which direction will the reaction shift to attain equilibrium? (adapted from LibreTexts)

Students also learn$^{\text{[citation needed]}}$ to "convert between $K_c$ and $K_p$" and to use $K_c$ in ICE (initial, change, equilibrium) tables to calculate quantities. Upon seeing all this my burning question is:
Do real world lab chemists ever express gas activities with molarity??
I have several theoretical and general objections:

How could anyone ever know what $Q$ or $K$ (unsubscripted) means for a general gas phase reaction, since $K$ is usually unitless (since activities are unitless)?

We can compare $Q$ or $K$ with 1 to see if a reaction is product- or reactant-dominant, either instantaneously or at equilibrium. But (for example) $K_c$ and $K_p$ will often differ by orders of magnitude and be on opposite sides of 1. What does that mean??

Don't heterogeneous-phase reactions get even more confusing, since gases could be quoted in either concentration or partial pressure? Do we need even more Henry's Law unit conventions?

Even if real world lab chemists wrote down gas molarities, it seems confusing enough that we should avoid burdening undergraduate students with these calculations. Evidence that students don't get it can be found on Chemistry SE here, here, here, here, here, here, or here.

But if it really is used often enough in professional lab chemistry to merit being in a first year chemistry textbook then I'll just have to teach it, I guess.

I assume molarities or mass concentrations may be useful for design of production open system processes in context of mass/molar inventory.

Kp is not considered dimensionless unless the partial pressures are expressed in bars (or the same units as the pressure in the standard state).

@ChetMiller If I'm reading the IUPAC definitions of Kp and K correctly, it seems (by those definitions) $K_p$ always has units of pressure^(change of gas moles), $K$ never has units, and $K$ and $K_p$ happen to numerically coincide when $K_p$ is calculated in pressure units corresponding to the standard pressure. But I'm a computer nerd, and I'm sure you're right about how actual chemists communicate using those quantities.

Even though $K$ doesn't have a dimension, it is defined relative to "standard conditions." (In the thermodynamic formulation, the change in Gibbs free energy is relative to a standard G.) If you went to a remote island where they defined a different set of standard conditions than you're used to, they'd have different values of K.

@anon I guess America counts as a remote island, since IUPAC's standard pressure is 1 bar and NIST apparently uses 1 atm!

You may want to consult a chem eng textbook as a reference.


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Can “hydrates” of crystals form with other molecules?
It is well known that copper sulfate, sodium sulfate, et al crystallize with 5,10 water molecules of hydration, locked in their crystal lattices. Is it possible to have other molecules instead of water, such as maybe ammonia or hydrogen sulfide?

Ammonia, yes. Lower alcohols, sometimes. H2S... never heard of such, but then again, I don't know everything.

$\ce{CaCl2}$ is known to form $\ce{CaCl2 . 6 H2O}$, $\ce{CaCl2 . 4 CH3OH}$, $\ce{CaCl2 . 3 CH3CH2OH}$, what is the reason, why this very good desiccant cannot be used for drying of ethanol (unless one wants to lose a lot of it.

Ammoniates - https://chemistry.stackexchange.com/questions/158408/does-solvate-isomers-exist-for-coordination-compounds-with-ammonia-solvent-as-li

Acetone and sodium iodide: https://doi.org/10.1039/CT9130301255

An examplle used for disinfection and synthesis is the compound of urea with hydrogen peroxide, $\ce{CO(NH2)2•H2O2}$. This is a shelf-stable source of hydrogen peroxide that readily releases the peroxide when dissolved in water.

Similar,  Sodium Percarbonate: 2(Na2C03) . 3(H2O2)

Yes!
Crystals with different solvents included are called, unsurprisingly, as 'Solvates'.
You can also just have a crystal of multiple molecules together and these are called 'Cocrystals'
A good, Open source paper on this published in the Journal 'Crystal Growth and Design' which is published by the American Chemical Society: https://pubs.acs.org/doi/10.1021/acs.cgd.6b00200


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What does the colon (the pairs of dots) mean in chemical structures?
What do the two dots mean, for example, the "Ö" in Wikipedia.org - Hydroxonium-cation.svg

30 characters limit is the system feature against the users who do not bother with topic research before asking nor with the question elaboration. Such questions are almost universally closed as Homework with lack of effort or a post with lack of details. Answering them would increase redundancy of internet.  // Review the guide How to ask and Asking FAQs to prevent clarification requests, objections,  down-voting or closure.

Please provide more details. Otherwise, it will be closed as Homework.

Well, it ain't an umlaut...

@Mithoron My answer is terse for a reason ...

@IanBush I was rather intending to criticise the question, than answer. Your post is fine for it, but should be rather a comment. I don't imagine we're gonna keep this q. too long.

@Mithoron and that's how I took it, no worries

Actually, I also want to delete it now.

It represents a lone pair of electrons in a Lewis Structure.


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How does one obtain K and stoichiometry from the Isothermal Calorimetry binding curve?
In Isothermal Calorimetry, I can appreciate that data is fitted to equations to obtain $K, \Delta H, \Delta G, \Delta S$ and stoichiometry, $n$.
However, I have seen from multiple sources that $K$ and $n$ can be obtained directly from the graph of enthalpy change against molar ratio of ligand added as such:

Obtained from wikipedia: https://en.wikipedia.org/wiki/Isothermal_titration_calorimetry
Where $n$ is the midpoint of the binding curve and $K_a$ is the slope (?) of the curve at what seems to be the midpoint.
But can also be seen here:https://www.youtube.com/watch?v=o_IpWcWKNXI&ab_channel=MalvernPanalytical (Just to show that the graph can be seen from multiple sources)
I can't figure out intuitively or mathematically why the $K$ and $n$ can be obtained directly from the graph as such. I have tried (taking $M_t = 1$ and $V_0 = 1$) substituting $Q = \frac{\Delta H}{2}$ into equation 7 from this document as well as differentiating equation 7 with respect to $X_t$. The results do not seem to agree with what the graphical method suggests.

Well, not directly, but with a bit of calculating...


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What resin is appropriate for construction of a gasoline/ethanol fuel tank
I am building a epoxy resin/glass reinforced plastic (epoxy/GRP) gasoline tank. The expected service life is 30 years.
I've read that epoxy is relatively resistant to gasoline (some better than others) but will suffer surface deterioration with ethanol additives. I've been told by industry reps that vinyl ester resins are superior to epoxies for chemical resistance.
But I can't find data sheets on retail-level available resins that would be good for this application. I've heard that underground storage tanks at gas stations are all GRP, so there must be a resin which is appropriate. Suggestions?

While this certainly involves chemistry I suspect this and the related question might be more appropriate for https://diy.stackexchange.com/

Or https://mechanics.stackexchange.com/

Because of liability due to gasoline (petrol) storage hazards, e.g., fire, soil and groundwater contamination, etc., I'd suggest you use an approved storage container.
Each locale has its own gasoline storage requirements, such as Canada, the United States, the United Kingdom, and there may be other regulations within a region, such as the state of Idaho.
Not only are there regulations on  the container itself, but also on additions, such as an outer container, fire suppression, etc.
Consult the petrol storage container manufacturers' literature in your area to see what is acceptable practice, but don't roll your own.

This project is a fuel tank for a motorcycle. Since it is smaller than most jerry cans, I think I'll dodge the regulations and do what is reasonable.

The question should have included that fact. 2. There are still structural, as well as chemical, requirements that need professional advice. Try https://mechanics.stackexchange.com/


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Why is melting spontaneous when the liquid phase is less stable and should have more free energy than the solid phase?
Imagine a 1kg block of ice that has completely melted at room temperature. If melting is a spontaneous reaction, then wouldn't that mean the products (1kg of water) would have less Gibbs free energy than the reactants (1kg of ice)? I am confused because water is more disordered than ice and less stable, so it should have more free energy than ice.

Note that the Gibbs energy change of phase transition is temperature dependent, being zero at the melting point.

The liquid phase does not have more free energy than the solid phase (when the liquid is stable).
True, the liquid has more total energy, or more accurately more enthalpy (which is essentially internal energy plus the work put into it from the outside pressure). But part of that energy is tied up in the greater disorder, or entropy, of the liquid versus the solid. When you add everything up according to the relation $G=H-TS$, the bigger enthalpy ($H$) of the liquid is outweighed by the bigger entropy ($S$) if the temperature ($T$) is high enough. Then the liquid has less of its energy as free energy.

If the temperature is high enough, as in greater than 0 degrees celsius? Also, this would mean that in a Gibbs free energy diagram, the curve at the liquid phase would be lower than the same curve during the solid phase?


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A water molecule is bent. Why?
Consider the bent shape of $\ce{H2O}$ with a bond angle of $104°$. From my understanding, this is due to the lone pair repulsion between the 2 pairs of lone pair electrons. Hence, it adopts a tetrahedral structure, with a smaller bond angle due to the 2 lone pairs. We know this from VESPR.
However consider the following diagram

What is inherently wrong with it? To me, it seems that $\ce{H2O}$ could adopt this linear shape without violating any rules. As its symmetrical, the repulsions should essentially cancel each other out, leaving this linear shape. However, obviously this structure is not possible. So what is wrong with it? Why can't the lone pairs be situated on opposite sides as such?
Furthermore, wouldn't placing the lone pairs on opposite sides maximise this distance between them. Hence shouldn't the above be favourable?

Chem+Math Expression formatting reference:
MathJax Basics / Chem+Math expressions/formulas/equations / Upright vs italic / Math SE Mathjax tutorial
// MathJax is preferred not to be used in CH SE Q titles.

It's due to the molecular orbitals, the angular spherical $s$ orbitals of the Hydrogen atoms should overlap with two $p$ orbitals in two orthogonal directions, to achieve this geometry the bond cannot be linear otherwise the overlap will only be with one $p$ orbital and the state will be higher in energy.

You mentioned that it adopts a tetrahedral. Take a look at this image of a tetrahedral:

Let's take a look at some possible positions the lone pairs (denoted by purple) can be.

As you can see, no matter which two places you put the lone pairs, the structure will be identical (they are all the same, just rotated).
So, while it may look like it based on the lewis structure, the lone pairs cannot be on "opposite sides," they will always be next to each other.

Thing is, in OP's scenario water would be rather "sqare-planar" than tetrahedral.


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Chloramines & Nitrogen Trichloride vs Stainless Steel
We've recently experienced excessive corrosion on stainless steel within indoor pool environments. We believe this is due to chloramine (gasses) in the atmosphere. To test this, I plan to create a small, closed environment (loosely sealed to contain gas but limit pressure buildup), in which I'll mix a solution to create some chloramines and hang material samples.
I assume (not from chemical background) that introducing pool chlorine (granular calcium hypochlorite 70%) and ammonia (as cloudy ammonia NH3 20g/L) to water, will kick most of this off. Attempts to maximise chloramines (Fig.1) will hopefully be achieved by keeping chlorine levels below breakpoint (Red local minimum - Fig.2)

I am slightly concerned after reading some articles and forums stating nitrogen trichloride (trichloramine) can be explosive. This factsheet states its only formed 'after breakpoint'. Additionally, some say 'in sunlight, will decompose', whilst others show it exploding in sunlight
Can anyone provide advice on how to safety generate monochloramine and dichloramine gasses without generating dangerous amounts of nitrogen trichloride?
I have an (ancient) Palintest photometer to monitor free/total chlorine but does not display ammonia.

At low pH values, nitrogen trichloride dominates and at pH 3–5 dichloramine dominates. These equilibria are disturbed by the irreversible decomposition of both compounds

A dilute solution is irritating not explosive. But don't try to concentrate it or extract it.

@matt_black for clarity we are trying to encourage some chloramine gasses buy placing the container in the sun with a glass top and some reflecting panels to introduce some heat, like a low-powered solar cooker. The unit is not well sealed so pressure buildup should be able to escape. I'm curious though, at what point does encouraging some generation (and degradation in UV) become 'concentrating'? I currently have no means of measuring specific chloramines, only 'Combined Chlorine'

I'm also very new to the StackExchange, can someone please explain why I'm receiving downvotes? Would love to learn more and better contribute to these forums.

For starters it's a Q&A site, not a forum... While pure NCl3 is explosive (kinda surprisingly) its dilute solutions aren't. I still don't get what you're trying to achieve there, and the post requires some copyediting.

@Kuhrta if you want to know what not to do you should watch this

@Mithoron thanks for clarifying. I've edited the post but was unsure if information or clarity was the lacking component. Also, when you say 'dilute solution' does this include vapour state in a high humidity environment?

Why chances of "boom" would be really small, all these compounds are dangerous. I wouldn't try such experiment. Better analyse water (or air), check quality of steel and compare with data that are already available.

@Mithoron part of the testing is comparative between specific coatings/treatments to the steel, to see how they interact within a high chloride/choramine environment. This paper Stress-Corrosion Cracking of Austenitic Stainless Steel in Swimming Pools, found that it's a unique phenomenon and were unable to replicate in lab conditions.

It seems like the chloramines/chlorides attack/crack the chromium oxide layer that protects austenitic stainless steels. Thus, existing literature regarding corrosion of stainless steels and other materials (predominantly quantified by salt-spray testing) will not be situationally accurate. Our company has taken that approach so far (49-years strong) but still seeing issues.

Fair enough, I guess, but you'd have to be real careful with concentrations, pressure, gas removal, etc. etc.

Careful is the name of our game. To monitor this i've still got some queries (Edited in Post) RE: PPM vs mg/L and 'Molar Ratio'


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What are the key differences between combustion of starch and sugar
I performed an energy content experiment the other day using a rudimentary bomb calorimeter. The experiment was comparing for the energy release of a sugary food (Arnott's Tiny Teddies) to the energy release of a starchy food (Water Cracker).
It was observed that the starchy food was much easier to ignite and was kept alight for longer. The sugary food needed a lot more heat to ignite and didn't stay alight for as long.
In the results it was found that the starchy food released less energy per mass compared to the the sugary food.
Is there any obvious reason why the starchy and sugary foods burn this way and release these relative amounts of energy? I assume it may be due to the chain structure of amylose/amylopectin compared to the smaller structure of sucrose, but I'm not 100% sure.
Thanks!

I assume the ignition heat value has been involved in the energy balance.

The samples were heated over a Bunsen burner to initiate the flame. This does result in an error of mass loss while the sample is not underneath the water (used to calculate the energy released).

You should describe in the question all relevant details of the experiment. Otherwise it leads to guessing and possible misinterpretation. // Generally, the calorimetry does not care about combustion kinetics assuming the combustion is complete and all energy flows are considered.

You are looking at three different things, two somewhat related. One is the ease with which you ignite the substances, the second is how long they burn, the third is how much energy they release. That last question can be answered with fair precision if you know the weight and composition.

Is there any obvious reason why the starchy and sugary foods burn this way and release these relative amounts of energy?

No, because the experiment did not test pure starch and pure sugar. The water content plays a role in flammability (does not burn, takes energy to get into the gas phase), and the fat content plays a role (burns very well, and is more exothermic per gram of fuel than carbs).
Here are two random food labels resembling your materials:
Honey tiny teddy:

Some brand water cracker:
Water content
For the cracker, the mass of carbohydrates, fats and proteins adds up to 29 g for the 30 g serving, so there is little water (it's a cracker).
For the cookies, non-water ingredients add up to 24 g for the 25 g serving, so also quite dry.
Fat content
The cookies have about 13% (by weight) fat, the crackers about 17%.
Starch vs. Sugar
You have to add water to starch to break it down to simple sugars. You could write a thermodynamic cycle to see how this influences the comparative energies of combustion (or enthalpies, if you are working with constant pressure).


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Are there tenebrescent minerals like KCl, but ideally resettable with UV/IR?
Is there a ‘simple’ mineral that is tenebrescent (getting reversibly darker on irradiation), but is resettable with UV or IR?
Hackmanite, spodumene and tugtupite (Wikipedia examples for tenebrescence) are only resettable by heating. $\ce{KCl}$ undergoes its color change on being bombarded with electrons in the $\pu{9 kV}$ range (that’s fine), but is also only resettable by heat.
I am looking for a (ideally ‘simple’, aka not sodalite $\ce{Na8(Al6Si6O24)Cl2}$, though I admit to not having a clear cutoff between that and sylvite $\ce{KCl})$ mineral that undergoes a color change in the visible spectrum on any kind of radiation, but is resettable by radiation in $\pu{300 nm}$ to $\pu{2500 nm}$ range.
Is there such a thing?
Is there a list?
Is there a way to predict this?


text:
Ablation of pyrolitic graphite utilizing electrochemical means
I am looking for a process to ablate the surface of a pyrolytic graphite (PG) sample.
I am thinking that an electrochemical process might be the answer; however, since this is not my field, I am looking for input from the experts on this forum.
I propose utilizing an electrolytic cell containing a strong acid electrolyte (ie. H2SO4) and a platinum electrode. The PG sample acts as the cathode and the Pt electrode is the anode. A 10V DC source is applied to the system in order to enable the ablation process.
I chose this method since it is an approach used to exfoliate graphite.
It is optimal for the process to be expedient, of which, this is not. So, any alterations to this method or alternate methods to expedite the process would be helpful.

What is the meaning of "to ablate the surface" ?

To create surface roughness by eroding the top layer(s) of graphite in the PG stack. For example, to create multiple indentations on the surface.

Don't you think putting the graphite at the anode would not be a solution of the problem ?

I do see that a paper I referenced https://pubs.acs.org/doi/10.1021/ja5017156# does designate the graphite as the anode and the Pt electrode as the cathode. Thanks for the correction.

Assuming that this is a viable solution to the problem, the question still remains - Is their an alternate solution that would expedite the processes of erosion?

The corrosion is much faster if the surface be corroded is at the anode.


text:
Oxidize Zinc or Nickel in black nickel plating to get browns?
I have a black nickel plating solution that is comprised of the following:
Nickel (II) Sulfate (45-50% by weight)
Zinc Sulfate Heptahydrate (20-24%)
Ammonium Thiocyanate (20-23%)
Zinc Chloride (1-3%)
I plan on plating brass.  Once I plate the brass with the black nickel, is there anything I can apply to get the black nickel to oxidize into browns?  Would a soak in hydrogen peroxide do anything to the zinc or nickel to produce browns?
I know its possible, just don't know how.

It is difficult to imagine a solution containing about 90% of solids like nickel and zinc sulfates, plus others. Are you sure it is a solution ? Is it not the composition of the solid stuff to be dissolved in water later on ?

I pulled the breakdown from the SDS sheet.  It is already dissolved in water, I guess they don't list water as an ingredient.
https://caswellplating.com/content/sds/Black%20Nickel.pdf

So which volume of water is used to dissolve $1, 10$ or $100$ grams of this mixture ?

I called the provider and they didn't know the amount weight of ingredients in the solution  All i know is the bottle is 8oz total volume liquid (water+ ingredients) and the SDS sheet lists what I listed above.
https://caswellplating.com/content/sds/Black%20Nickel.pdf


text:
Mixing two solutions: how to solve such problems, is there a trick?
Two containers were filled with salt solutions, and the first container contained 1 liter less solution than the second. The mass concentration of salt from the solution in the first container was 10%, and in the second, 20%. After both solutions were poured into the third container, a new solution was obtained, the concentration of which was 16%. How much solution (volume) was in each container initially?
I just wonder how such kind of problems are solved. I'd be very grateful if you help me to understand. It's from 7th grade.

This is mostly a linear equations math problem. Let $x$ be volume of 10% solution and $y$ be the volume of the 20% solution. Now you need to figure out two equations that relate $x$ and $y$. //  The only "chemistry" part is assuming that the volumes of the different solutions are additive, which isn't absolutely true. However the overriding consideration is that the concentrations of the salt solutions have only been given to two significant figures, so assuming the volumes are additive is reasonable.

@MaxW But volume additivity is not the only problem, as the mass percentage refers to the solution mass, not volume, so solution density would be needed. It is possible the task neglects density difference.

For 2 kg 10% solution is needed 3 kg of 20% solution. What particular masses to use to have 1 L difference depends on densities of both solutions. 2 and 3 L would be applicable only if densities of 10% and 20% solutions are the same, what is not true. But it is possible the task is oversimplified for the 7th grade and they go this way.

@Poutnik - You're correct, nice catch! There isn't enough information given in the problem for a solution. The problem is that the solution concentrations are expressed as weight %'s, but the difference in the two solutions is given in liters. In order to make the problem solvable the difference between the solutions should have been given as a mass, not a volume.

@MaxW showed the procedure for doing this problem in the comments, so I'll just show that procedure applied to your specific example. We will assume the volumes are additive.
let $a$ represent the volume in liters of the first solution, $b$ represent the volume in liters of the second solution, and $c$ represent the volume in liters of the combined solution.
We have two equations:
$.1a + .2b = .16c$
$a+b=c$
We know from the problem that $a=b-1$, so let's make that substitution:
$.1(b-1)+.2b=.16c$
$b-1+b=c$
Now, lets solve that bottom equation for c, so we can write everything in terms of b:
$2b-1=c$
Now, substituting $c=2b-1$ to the first equation:
$.1(b-1)+.2b=.16(2b-1)$
Now, we just solve for b:
$.1b-.1+.2b=.32b-.16$
$.3b-.1=.32b-.16$
$.06=.02b$
$b=3$
Now that we have b, we can easily solve for a:
$a=b-1=3-1=2$
So, there were intially 2 liters of the first solution and 3 liters of the second solution.

The task description is flawed, as it incorrectly assumes 10% or 20% solutions contain $\pu{100 g/L}$ resp. $\pu{200 g/L}$ and that mixing of solutions does not change the total volume.
But if they used

either mass percentages and solution masses
or mass concentrations and assumption $ΔV=0$

then they could directly use the mixing rule:
$$\frac{m_\mathrm{10\%}}{m_\mathrm{20\%}} = \frac{|20\%-16\%|}{|10\%-16\%|} = \frac{2}{3}$$
$$\frac{V_\pu{100 g L-1}}{V_\pu{200 g L-1}} =
\frac{|\pu{200 g L-1} - \pu{160 g L-1}|}{|\pu{100 g L-1} - \pu{160 g L-1}|} = \frac{2}{3}$$
and directly used as the task solution:

Mass percentage:

10% solution:  $\pu{2 kg}$
20% solution:  $\pu{3 kg}$.

Mass concentration:

$\pu{100 g L-1}$ solution: $\pu{2 L}$
$\pu{200 g L-1}$ solution: $\pu{3 L}$.

For the mass percentage case, solution densities would be needed to calculate volumes.


text:
Question on Lithiation Site in Directed Metalation
I have seen this from the Baran group meeting material
Here, why does lithiation not happen at C2 position? Why does tBuLi specifically litigate the C4 position only?

Do not underestimate the steric bulk of the TIPS group. Have you read the referenced articles? They may comment on this. They may also indicate whether any C2 lithiation was observed.


text:
What shifts protons on a benzene ring to lower ppm?
Why do these protons appear at 6.9 and 6.93 ppm, at lower ppm value? I assumed it was due to the anisotropic effect, specifically I thought the circulating (pi) electrons induced a magnetic field which causes them to experience a stronger net field, and those that were lower were not being affected by the induced magnetic field. This is instead apparently due to resonance. How come it is due to resonance? Is the circulation of electrons (ring current) not affecting them all or instead is resonance the primary reason why some protons come lower than others?

Yep its due to resonance I don't know what else there is to explain!

Review the guide How to ask and Asking FAQs to prevent clarification requests, objections,  down-voting or closure.

It’s due to resonance as the methoxy group is an ortho-para electron-donating group by resonance.
Hence the ortho and para positions are more electron rich, so their protons are more acidic and further downfield.

This is the textbook explanation. Here is a paper beyond the textbook, also considering the sigma electrons.


text:
Why does Williamson's Ether Synthesis ONLY follow Sn2 Mechanism
I am a high school student learning chemistry and my knowledge of organic chemistry is very limited, so pardon me if I am asking a nonsensical question.
While practicing organic, I came across the following question:

Now my thought process was, option A takes place through Sn2 mechanism and if option B must take place it would through Sn1 mechanism. My chemistry teacher told me that if the reacting halide is tertiary, it would prefer Sn1 pathway and a primary halide prefers Sn2 pathway.
The answer says option A is correct because Williamson Ether Synthesis follow Sn2 pathway all the time. Why can it not follow Sn1 pathway, under the right circumstances (a polar protic solvent), which would make both reactions feasible.
Some of my friends said that an elimination reaction takes place here and Sn1 isn't possible because of the elimination reaction. But why is Sn1 not possible?

Problem doesn't lie in formation of carbocation intermediate. Chlorine could easily be removed. But main problem is that the carbocation we got now would easily lose hydrogen from $β$ carbon in presence of strong base and would form double bond bond. Elimination is highest in tertiary and lowest in primary. Steric hindrance is 2nd reason as 3 alkyl groups would come in way of alkoxide anion. To overcome hindrance it follow sn1 and lose chlorine but now our carbon would be free to form double  bond and again we would not get ether.

Ohh, that makes sense, so elimination is more favourable over Sn1 and thus happens much more quickly, but that doesn’t mean that Sn1 isn’t feasible right? Does the Sn1 pathway not take place at all, even under the right conditions? Or is it just less favourable?

Less favourable and accompanied by a lot of alkene formation

Ahh okay thanks a lot to both of you. I think I am clear now. I really appreciate your help. Thanks a lot!!!

Option A could not be SN1 as that would lead through the formation of a primary carbocation which is too unstable.
However, there might be a mistake in the answers as A isn’t really feasible given that the tert-butoxide is too sterically-hindered to be very nucleophillic, especially when substituting for a large bromide ion.


text:
Why is cyclohexane more polarizable than benzene?
Looking at figure 4.2 here, we can see experimentaly that cyclohexane is more polarizable than benzene.
Why is this the case?
Intuitively, I would think that because the orbitals in benzene are more delocalized, the electrons in benzene could move farther in reaction to an applied electric field, thus creating a larger dipole and being more polarized than what is possible in the localized orbitals of cyclohexane.
The only counter argument I can think of is that the carbons in benzene are SP2, and thus more electronegative than the SP3 carbons in cyclohexane so that even though the electrons have more space to react to an applied field in benzene, they are held tighter to the nuclei and therefore form less of a dipole. However, something about this argument doesn’t seem convincing to me.

Cyclohexane has more hydrogen atoms and its C-H bonds are less polarised, leaving more room for distortion of existing electron cloud.


text:
Can acid-base reaction occur if two compounds (one acidic and one basic) are added to each other while being in their molten states/pure form?
I am a 14 year old school student and have been told that acid-base reactions occur in aqueous solutions only for they produce ions in aqueous solutions only and I can’t help but wonder if they can take place if these two kinds of compounds are added to each other in their pure forms or molten states.

If they can intimately mix then there will be reaction. In solid state this is very slow, it can occur in molten state. There are also other solvents that support the formation of ions.

To get an acid-base reaction, the reagents (and ions) must be mobile. They are not in the solid state. So mixing a solid acid an a solid hydroxyde will produce a reaction limited to the contact points, which can be neglected. If the reagents are molten, they are mobile. It looks like the situation in an aqueous solution. The reaction can take place, but it is not so fast as in aqueous solution.

If can happen even in gaseous state.

Good question! I'm not an expert at all here but a quick look suggests solid state acid-base reactions are an active area of research - for instance https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiYlOu-xs2BAxWZUEEAHWc_D3cQFnoECCwQAQ&url=https%3A%2F%2Fdocs.lib.purdue.edu%2Fcgi%2Fviewcontent.cgi%3Farticle%3D2511%26context%3Dopen_access_dissertations&usg=AOvVaw29kNAMTEXg6UfIB_GmDZ15&opi=89978449 discusses solid state acid-base in pharmaceuticals, and https://en.wikipedia.org/wiki/Solid_acid touches on mixed phased reactions

Another example is the use of zeolites in a number of areas as solid state acids, including the multimillion pound  area of cracking in the petroleum industry

Does this answer your question? Can acid-base reactions occur in a non-aqueous medium?

The key question we must ask ourselves is which definition of acids and bases we wish to employ. Since acid and base is a man-made label for chemical compounds, then we must familiarize ourselves with plenty of acid-base definitions that were proposed by different scientists over a century. You will study these definitions in higher classes. When we restrict ourselves to aqueous solutions, we are using a very narrow and limited definition of acid and bases, which is fine for elementary classes. Therefore the acid-base reactions can occur in any state.

Gas-phase: The classical reaction of ammonia gas with HCl gas to form a solid ammonium chloride. (At a deeper level, a trace of water makes the reaction very fast, and but water vapor is always present in air)

Solid-gas: Carbon dioxide reacting with solid sodium hydroxide to form sodium hydrogen carbonate.

Reactions in organic anhydrous solvents: Acid-base reactions occur all the time in organic solvents. No water is there (anhydrous).

Similarly molten salts will react with pure bases or if you can melt them. Nobody does it regularly but in rare synthetic cases, acid base neutralization has been observed Reaction of molten sebacic acid with a layered (Mg/Al) double hydroxide.

Water is not required for acid-base reactions. The materials do not need to be ionized to react.
The comments have already given you some good examples, like the reaction between ammonia ($\ce{NH3}$) and hydrogen chloride ($\ce{HCl}$), both gases at room temperature. They react to form ammonium chloride, $\ce{NH4Cl}$, which is a solid. There is no water involved and the result of the reaction is a very fine white smoke. This is actually a fairly common classroom demonstration.
Some elementary chemistry classes give an incomplete definition of a base, which only includes hydroxides like $\ce{NaOH}$ or $\ce{KOH}$. That would exclude the previous reaction, which involves ammonia. This definition is bad and is never used by real chemists, only in the classroom. But even under this definition, water is not required. Pure, dry $\ce{HCl}$ gas will react readily with hydroxides in their solid form. And if you were stupid enough to try adding molten sodium hydroxide to a pure liquid acid like sulfuric acid, the reaction would be very violent, and the whole caustic mixture would instantly explode in your face.
In fact, one reason to do a reaction in solution is to reduce the intensity of the reaction. You can safely mix very dilute solutions of acids and bases, while mixing the same chemicals at higher concentration could release too much heat too fast and explode.

Not to mention the "base" or "acid" could be water itself. We all know the precausions necessary when diluting, say, sulfiric acid (much heat release) or hydrochloric acid (less heat, but fumes) with water.

Looking more closely at the classic case of ammonia and hydrogen chloride gases without water:
Countess and Heicklen[1] carried out the reaction between gaseous ammonia and hydrogen chloride in anhydrous nitrogen, demonstrating the raction without need for either liquid or gaseous water. They give a rate constant for this reaction.
What actually happens is that the strongly polarized hydrogen from the hydrogen chloride first hydrogen-bonds to the nitrogen from the ammonia, thus forming ammonia-hydrogen chloride clusters. In the absence of water the initial $\ce{H3N–HCl}$ cluster is not ionic, but as the cluster grows further the hydrogen-bonded protons become fully transferred to make the $\ce{NH4^+}$ and $\ce{Cl^-}$ ions, which ultimately are assembled into the solid-phase lattice. This is discussed more fully here.
Reference

Richard J. Countess and Julian Heicklen, "Kinetics of particle growth. II. Kinetics of the reaction of ammonia with hydrogen chloride and the growth of pariculate ammonium chloride", J. Phys. Chem. ,1973, 77, 4, 444–447.


text:
Is size or electronegativity more important in acidity?
For the molecule below, is the hydrogen with the oxygen more acidic or is it the one with sulfur?

Since both parts have the same number of resonance structures, I'm guessing it just boils down to whether or not an atom's electronegativity or size takes precedence in determining whether the proton is more acidic.
So, is size or electronegativity more important in acidity?
Thanks in advance!

The size is more significant and the thiocarboxylic acid would be more acidic.
Whilst electro negativity facilitates the stabilisation of a negative charge, the larger size of the sulfur both:

Makes the S-H bond weaker than the O-H bond.
Helps to stabilise the negative charge on the sulfur.

Hence sulfur derivatives are usually more acidic than their oxygen counterparts. H2S more acidic than H2O and thiols more acidic than alcohols, etc.

I think you mean the dithiocarboxylic acid

Yes sorry thanks for the correction

Ic that makes sense. thanks :)


text:
Explain the mechanism of the following reaction, which involves a 1,2-alkyl migration with double inversion of configuration
I came across the following reaction, whose mechanism is said to involve a 1,2-alkyl migration with a double inversion in configuration. The reagents used were nitrous acid (generated in situ) followed by acidic hydrolysis.

I got a hint that the first step involves the reaction of nitrous acid with the NH group. But, I cannot understand how the reaction works. Could anyone explain the mechanism?

Are these structures correct? As drawn the product has gained a methyl group at the top which has no apparent source.

There was a mistake in the structure I drew. Thank you for pointing out.

The OP's original structure is missing a quaternary methyl group (since amended) because the structure 1 is derived from α-santonin[1] with hydroxylamine. Nitrosation of 1 affords 2 that undergoes acid-catalyzed fragmentation to give secondary carbocation 3. A suprafacial 1,2-methyl shift produces tertiary cation 4. Two fates of carbocation 4 may be considered. One is to form intermediate 7 that loses nitrous oxide to give epoxide 6. Alternatively, carbocation 4 loses nitrous oxide forming alcohol 5, which undergoes ring closure to form epoxide 6. These mechanistic considerations are not discussed in the reference.

J. T. Edwards and M. J. Davis, J. Org. Chem., 1978, 43, 536. https://doi.org/10.1021/jo00398a002


text:
Measurement of the number of electrons, protons and neutrons inside an atom
How do we measure the number of protons, electrons, and neutrons inside an atom? What experiments can be conducted to determine, for example, that an iron atom contains 26 protons?

We do not measure the number of protons, electrons, and neutrons inside an atom. If you know it's an atom of iron then there's hardly a reason to reinvent a wheel. If it was an unknown atom, then still identification that it's iron or something else would be simplest.

If for some reason you wanted to waste you're time on that, then you could completely  strip your atom of electrons and measure the charge of the nucleus - if its 26 times higher then elementary charge, than there's 26 protons. Unless you somehow doubt the value of the charge of proton?

This is a whimsical suggestion to even think of stripping all electrons of an element to determine the number of protons in iron!

@AChem In accelerators it's done all the time. Mass and charge can be measured pretty easily from behaviour or the nucleus in the magnetic field. Obviously it's not a "chemical" method, but I already mentioned chemists don't measure such things.

The number of protons, neutrons, and electrons in most of the natural elements were indirectly deduced long before accelerators were used to create new elements.

Well, OP should clarify whatever he really wants to know! Right now it's "What experiments can be conducted", not how we know it - which is much better question and I'm pretty sure was already asked here.

There are no techniques that directly count the number of electrons, protons and neutrons in an atom. All deductions about basic atomic structure were established indirectly, well before the 1940s with the help of chemical properties and purely chemical measurements of atomic weights. No machines needed except a highly accurate mass balance. One would determine the atomic weight of iron from quantitative chemical reactions.
It will not be wrong to say that it was purely the empirical periodic table led to our basic conceptions about the atomic structure. None of the fancy techniques mentioned in the other answer such energy dispersive X-ray spectroscopy or particle induced X-ray emission were there to count or probe the atomic structure. These are analytical techniques and need calibration, i.e., someone has to tell the instrument that this frequency is associated with a certain element.
Chemists had already deduced chemical properties and arranged them in a "periodic" table showing that chemical properties repeat periodically like periodic mathematical functions more than 100 years ago. The chemical elements, then known, were also roughly arranged according to the atomic weight (or atomic mass today) not by atomic numbers as done today. Physicists started to probe this arrangement deeper and deeper and this is where X-rays started to help explain this periodic phenomenon of chemical properties.
It was young Moseley's X-ray work that established that the ordinal number of the elements (let us call it $Z$) in the periodic table was related to frequency of the X-rays emitted by each element. Since Bohr had established that hydrogen has a Z=1 with one proton, it was Moseley's intuition that led to the proton count of the elements.
By electrostatic theory, the positive charge must be balanced by negative charges. So the number of protons must equal the number of electrons. The last question is number of neutrons: The number is neutrons was deduced, again indirectly, from atomic masses because the mass of the protons did not add up to the atomic mass. Something "else" was there, and this was the mass of neutrons. Mass spectrometry also established isotopes.
So back to your original query: How do we know that iron has 26 protons...it is because of Moseley's law.

This is a useful answer, but the OP does not explicitly ask for a historical explanation. Also, intuition is not proof, so one might ask when Moseley's law became a law rather than remained a hunch.

@BuckThorn, If the OP knew the history he/she would not have asked this question.

Again, I do not mean to suggest that your post is invalid. My point is simply that the OP posed a broad question that does not imply a desire for an answer describing how these properties were originally determined. There are now other tools available.

@ Buck Thorn, That is fine what are the other tools that you have in mind that will directly tell us the number of electrons, protons or neutrons from absolute measurements (not by calibration matching of standards). I don't think there are any except ultrahigh resolution mass spectrometers.

None, I don't pretend to know. It's just that the OP asks "What experiments can be conducted to determine, for example, that an iron atom contains 26 protons?" Your answer is to run Moseley's experiment, evidently (which is ok). If you were handed a sample of iron, or better yet, an unknown pure elemental substance, and asked to determine the atomic number, how would you do so?

https://sites.science.oregonstate.edu/~schellmh/COURSES/ph314/Labs/9_moseley_lab.pdf

I think X-rays will come to rescue using Moseley's law by pure empirical pseudo ab-initio way, as if we were handling iron for the first time. Second option would laser ablating the sample and doing mass to charge ratio studies of the ions from the new element (iron).


text:
Why do samples of ionic compounds break into pieces, but the pieces do not combine into larger samples again?
A distinct property of ionic compounds is that they are brittle. We are taught this is due to the fact that when force is applied to the lattice, ions are shifted, resulting in positive ions repelling positive ions and negative ions repelling negative ions. As a result, the lattice shatters. Hence ionic compounds are brittle. Makes logical sense to me.
However, using similar intuition, could we not just as well take  the shattered pieces and hold them together again. At some point, we should get oppositely charged ions aligning causing the shattered pieces to come together again. Obviously when we hold, table salt together, they don't come back together. So what is fundamentally wrong with my intuition here?

It is not a distinct property of ionic compounds. Many molecular solids and even metals are also brittle. The causes of brittleness are far more complex than you think.

https://chemistry.stackexchange.com/questions/78947/broken-object-bonds

https://chemistry.stackexchange.com/questions/109246/why-is-graphite-brittle

Also, the same-ion repulsion explanation of why ionic compounds are brittle is nonsense. Iodine crystals are also brittle, but the explanation clearly doesn't worth there.

@matt_black Temperature equally plays a role, too.  As in the lectures where a piece of flexible rubber, or an apple becomes brittle after their immersion in liquid nitrogen.

OP said nothing about rubber, iod, or apples. ;) And of course the explanation is not complete, but it's also certainly not nonsense for ionic substances. We don't need to go into crack growth etc. here.

@OP almost perfectly matching surfaces would have to align perfectly. That's the problem.

Your intuition is not wrong... but the atoms near the surface have to be free to move or exactly aligned, and must not covered by an adhered layer of air.
For example, by dissolving a salt in water and letting the water evaporate, you can watch crystals grow, as atoms (well, ions) find their place in the lattice. Read Crystals and Crystal Growing by Holden and Morrison, for example, download a free classic, such as Tutton's Crystals, or look online, such as Science Notes, How to Grow a Crystal.
Of course, there are crystals of metals and non-ionic compounds, too. Consider that only mildly-ionic water vapor condenses to make snowflake crystals, investigated by Bentley.
Simply holding pieces in your hand and hoping the crystal structure to align ignores theses issues:

The surface of the crystals would have to be atomically smooth, not jagged. Examine the surface of even a carefully cleaved crystal under an atomic force microscope and you'll find few smooth areas. The jagged peaks and valleys prevent the surfaces from meeting except at a few points.

As soon as a crystal is cleaved in air, the surface is covered with an adhered film. Germer states in The Study of Crystal Surfaces, "One of the most significant facts about real surfaces is that they quickly become dirty; a freshly cleaved crystal
soon adsorbs foreign atoms on its surface." The effect is like using waxed paper to keep dough from sticking to surfaces.
However, given smooth surfaces, they do stick together in the process of cold welding.


text:
Understanding the Composition of Sodium Zincate (Na2ZnO2) Formed from Zinc and Sodium Hydroxide Reaction
I've recently conducted an experiment where I reacted zinc with sodium hydroxide to form sodium zincate (Na2ZnO2). However, I'm having trouble comprehending why sodium zincate has the composition Na2ZnO2. Can someone explain the chemical reactions and principles that lead to this specific composition? Additionally, what factors influence the stoichiometry of this reaction, and how does it relate to the properties of sodium zincate?

The eventual closure can be lifted if the user addresses closure reasons and asks for reopening.  Note that re-posting of an eventually closed question, instead of editing of the closed one, is frown upon and such a question would be closed too. ( See https://chemistry.stackexchange.com/q/176394/35806 )

Review the guide How to ask and Asking FAQs to prevent clarification requests, objections,  down-voting or closure.

Why can't the people who poorly answered my question review their answers?

Do yourself first what you require from others. Review your poorly formulated questions. What particularly you do not understand and what you did to get understanding before asking?

It's not a singular specifies. This refers to series of zinc oxides or hydroxides depending on reaction condition and can be interlinked together.

In fact both hydroxyzincates and oxozincates are known. Neither is described by any single formula; $\ce{Na2Zn(OH)4}$ and $\ce{Na2ZnO2}$ are simplified representations. The former are obtained in aqueous solutions, while the latter are produced in high-temperaure nonaqueous reactions using sodium oxide as the basic component.
Wikipedia gives a summary of known hydroxyzincates, which can be crystallized with different cations and different coordination of the zinc:

Solutions of sodium zincate may be prepared by dissolving zinc, zinc hydroxide, or zinc oxide in an aqueous solution of sodium hydroxide.[1] Simplified equations for these complex processes are:

$\ce{ZnO + H2O + 2 NaOH -> Na2Zn(OH)4}$

$\ce{Zn + 2 H2O + 2 NaOH -> Na2Zn(OH)4 + H2}$

From such solutions, one can crystallize salts of containing the anions $\ce{Zn(OH)4^{2−}}$, $\ce{Zn2(OH)6^{2−}}$, and $\ce{Zn(OH)6^{4−}}$. $\ce{Na2Zn(OH)4}$ consists of tetrahedral zincate ion and octahedral sodium cations.[2]
The salt $\ce{Sr2Zn(OH)6}$ features zinc in an octahedral coordination sphere.

Among oxozincates $\ce{Na2ZnO2}$[3], $\ce{Na2Zn2O3}$[4], and $\ce{Na_{10}Zn4O9}$[5] are reported in the Wikipedia article. Trinschek and Jansen, authors of all three of these references, report a solid-state synthesis in Ref. [3]:

By reacting $\ce{Na2O}$, which was produced in situ from $\ce{NaN3}$ and $\ce{NaNO2}$, with reactive $\ce{ZnO}$ in the solid state, the synthesis of $\ce{Na2ZnO2}$ has been achieved. $\ce{Na2ZnO2}$ is metastable up to about 750°C.

References

Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

R. Stahl , R. Niewa , H. Jacobs, "Synthese und Kristallstruktur von Na2Zn(OH)4", Zeitschrift für anorganische und allgemeine Chemie, 625, 48-50, doi:10.1002/(SICI)1521-3749(199901)625:1<48::AID-ZAAC48>3.0.CO;2-L

D. Trinschek, M. Jansen (1996). "Na2ZnO2, ein neues Natriumzinkat". Zeitschrift für Naturforschung B, 51(5), 711-714. doi:10.1515/znb-1996-0515

D. Trinschek, M. Jansen (1996). "Eine neue Modifikation von Na2Zn2O3", Z. Naturforschung 51b, 917-21.

D. Trinschek, M. Jansen (1996). "Ein neues Oxozinkat mit trigonal-planar koordiniertem Zink Na10Zn4O9", Zeitschrift für anorganische und allgemeine Chemie 622, 245-50.

Apart from its initial values zero, the element zinc has only one known oxidation number. It is +$2$. In this oxidation number +$2$, zinc appears in general as an ion $\ce{Zn^{2+}}$. It may also occur as a complex of the ion $\ce{Zn^{2+}}$ with water $\ce{H2O}$, or with the ions $\ce{O^{2-}}$ or with the ions $\ce{OH-}$. In aqueous solution, there is an equilibrium between both ions $\ce{O^{2-}}$ and $\ce{OH-}$, according to : $$\ce{O^{2-} + H2O <=> 2 OH-}$$ If we consider the only case of the ions $\ce{O^{2-}}$, they may produce with  zinc $\ce{Zn^{2+}}$ the following species with one or two ions $\ce{O^{2-}}$ :  $\ce{ZnO}$ or $\ce{ZnO2^{2-}}$
If the amount of $\ce{OH-}$ ions is weak in solution, the following reaction happens between zinc and water : $$\ce{Zn + H2O -> ZnO + H2}$$ but this reaction does not last more than a couple of microseconds, because $\ce{ZnO}$ is insoluble in water and stops the contact metal - solution.
If the amount of $\ce{OH-}$ is relatively important in solution, the following reaction happens after the first one : $$\ce{ZnO + 2 OH- -> ZnO2^{2-} + H2O}$$ so that the total reaction of the two last equations is : $$\ce{Zn + 2 OH- -> ZnO2^{2-} + 2 H2}$$ Apparently this last equation is exactly what uggupuggu is looking for.

Technically, zinc is known in the +1 oxidation state. But yes, in aqueous systems it will be +2.


text:
Temperature change when mixing different ratios of NaOH and H2SO4 solutions
Under the same conditions, mixing how many ml of 1M $\ce{KOH}$ solution and 0.5M $\ce{H2SO4}$ solutions to form a total volume of 100ml produces a rise in temperature?

If there is already the tag thermodynamics, the title thermodynamics question carries literally zero additional information, like a book title "The Adventure book" in the bookstore section "Adventure books". // The question itself as the English sentence is formulated in very confused way, words almost in a random order and it is  not trivial to guess wht is asked. // Note that questions looking like homework/test/exam/lab questions/tasks without written significant resolving attempts are explicitly off-topic on this site and will be closed.

Review the guide How to ask and Asking FAQs to prevent clarification requests, objections,  down-voting or closure.

What is the question  ? Is the "rise in temp" to be read as "rise of temperature" ?

@Maurice Or "What volumes...?".  It is not a question, it is a riddle or encrypted message.

What you've asked is a neutralisation reaction. Any amount of acid and base mixed together would cause a neutralisation reaction, and in general, neutralisation reactions are highly exothermic reactions:
$$\ce{H+ + OH- -> H2O}$$
The enthalpy change for this reaction is $\Delta_\mathrm{r} H = 57.62$ $  \mathrm{kJ/mol}$, which is pretty high. Also since both of your reactants are strong electrolytes, your heat of neutralisation is not pH dependent.
So, mixing any amount of the acid and the base to create a $100$ ml solution would cause a rise in temperature.

I don't think this answer totally covers the question. The molar enthalpy of generic acid-base reaction is useful but not fully explanatory.


text:
In which medium is Potassium Permanganate a better oxidising agent?
I was in chemistry class just now, and my chemistry teacher gave us three reactions:
Reaction 1: $\ce{MnO4^- + e- -> + MnO4^2- (basic medium)}$
Reaction 2: $\ce{MnO4^- + 4H+ + 3e- -> + MnO2 + 2H2O (neutral or nearly neutral medium)}$
Reaction 3: $\ce{MnO4^- + 8H+ + 5e- -> + Mn^2+ + 4H2O (acidic medium)}$
with n-factors of $n_1=1$, $n_2=3$, and $n_3=5$ respectively.
Now, the problem arose when my teacher stated that $\ce{KMnO4}$ was the best oxidising agent in the acidic medium. He said that this is due to the fact that $\ce{KMnO4}$ had the greatest n-factor when it was in the acidic medium. I decided to do a bit of fact-checking in my book (NCERT, which is the standard book we use in India) and I came across the fact that each of these reactions has reduction potentials of $E^⦵_1 = +0.56 \mathrm{V}$, $E^⦵_2 = +1.69 \mathrm{V}$, and $E^⦵_3 = +1.52 \mathrm{V}$ respectively, which lead me to conclude that instead, $\ce{KMnO4}$ is a better oxidising agent in the neutral medium, if we go by the experimental data of reduction potentials.
Besides this, my book also mentions that: "Although many reactions can be understood by consideration of redox potential, kinetics of the reaction is also an important factor. Permanganate at $\ce{[H+]}$ $=$ $1$ should oxidise water but in practice the reaction is extremely slow unless either Manganese (II) ions are present or the temperature is raised." It does not elaborate further, but this gives me a hint that somehow, the kinetics when it comes to this reaction matter as well.
An addition from my side: if we were to calculate the Standard Gibbs Free Energy from the given redox potentials, we would find that the most negative Gibbs Free Energy would be for the third reaction. Would this in any case have an effect? Since it's "more spontaneous", could we consider that it's a better oxidising agent in that case?
So my final question is, is the book correct or is my teacher correct? And if my teacher is correct, then how should I know to judge the oxidising nature through reduction potentials or through the n-factor? It seems that my teacher is giving more weight to the stoichiometry, and the book to the kinetics and thermodynamics.

Define better, as there are multiple possible weighted criteria. (Thermodynamics, kinetics, stoichiometry ratios, stability of reagents, price etc). Reduction potentials are just one of them.

Could you elaborate on what you mean by "possible weighted criteria" please?

Both can be correct because "better" is subjective parameter. The book and the teacher could use different criteria set and their different importance and therefore their result need not be the same.

Related: https://www.researchgate.net/publication/281434219_Applications_of_Potassium_Permanganate_in_the_Oxidative_Degradation_of_Trichloroethylene

@ShivanshJaiswal Not in the title. And the body considers thermodynamics, kinetics and stoichometry. Each of them contributes to "better". The teacher gives more weight to stoichiometry, the book to thermodynamics and kinetics.

@Poutnik Alright, got it. I have one more question if the Nernst Equation affects anything, I'll edit it into the question.

Both the Nernst equation and acid-base equilibrii affect redox reactions. They have two sides: the oxidant and reductant. If KMnO4 gets weaker and reductant is stronger with higher pH, is KMnO4 better or worse oxidant at higher pH?

See also commons.wikimedia.org - Mn Pourbaix diagram.png // The two dashed inclined lines are pH dependent potentials for oxidation and reduction of water.


text:
Effective Core Potentials and their "corresponding Pople" basis set
Reading through a handout from Yale shows the author correlating the ECP with Pople basis sets. The author of this says the corresponding basis set for SDD is 6-31G, Def2TZV as 6-311G, LANL2MB as STO-3G, etc... I'm confused between the correlation between the two, as I thought they were entirely different sets of LCAO's that can't be directly correlated. Are a portion of one of these ECP's constructed with Pople basis sets? Or am I misunderstanding?
Direction (link to a publication, article, etc) would be greatly appreciated so I can clarify my misunderstanding and learn about this, and clear any gaps in knowledge. Thank you.

It seems  that you misunderstood the handout. There is no equivalence between the basis sets that include ECPs and the Pople basis sets. It just tells you that if you were to use one of the basis leftmost column  of the table (e.g. LANL2MB) you would have a basis set of a similar type (number and kind of orbitals) that the corresponding Pople's type basis (STO-3G). However, details of the orbitals (CGTOs)   are diffent in both basis.

You may find help Lewar's book on Computational Chemistry (E. G. Lewars, Computational Chemistry, 3rd ed., Springer, Netherlands 2016 ). Section 5.3. on basis sets is a good introduction to the basiscs. There are other excellent textbooks on the topic.

Hi @PAEP , I went through my old post and saw I didn't thank you for your help. The book recommendation was great and I can see where my confusion got me completely derailed. Thanks!


text:
Programs to view or convert unformatted Mass Spec data
I've been give mass spec data in very simple format .txt files. Each file is two columns, m/z and intensity. There is no header or anything. Are there any programs that can read this file? Or how can I convert this to a file readable by a program such as OpenChrom.
I know I can use Excel, but I'd really like the functionality of dedicated MS programs (simulated peaks, zooming, etc).
UPDATE: Some extra info for anyone with similar issues in the future. The MS measurements were performed via direct infusion on a Waters brand MS. I learned that Waters output files are notoriously opaque, which is part of the reason I was given a .txt output. I asked for the original files and got them. I was able to convert the raw files to mzML with MSConvert from proteowizard. OpenChrom was then able to open and view the spectra. At this point, it's merely a matter of me learning the best software to do what I want to do, i.e. view the full, combined spectra of a direct infusion MS measurement, then pick the picks and export those with predictive spectra.
Thanks to everyone who took a look at this and provided insight.

Not familiar with that particular software. Your TXT file is an ASCII file and you can open it with a text editor (Notepad, NotePad++, etc). Usually this kind of files are also written with the extensión DAT and CSV (Comma Separated Values). In the web page of OpenChrom indicates that it can read TXT and DAT formats so you could probably read those data directly in the program.

@PAEP OpenChrom can recognize and open the .txt from File>Open Chromatogram, but there are no visualizations at all. I believe that since there is no actual chromatogram data, just MS peaks, OpenChrom either can't interpret it or I don't know how to make it do so. Thank you for your quick reply.

A simple approach can rely on gnuplot, which is freely available at least for the Windows, Mac, and Linux operating system.  It is not a dedicated MS program to simulate fragmentation patterns / predict the intensity of the $\ce{^{13}C}$ peak next to the one of the molecule ion, but provides you a quick visualization of the data recorded.
Because you don't state if the two columns in question are separated by space, or by column, I assume they are space separated.  This is a pattern e.g. for mass spectra in the AIST Spectral Database.  Let's depart from the MS data for their entry 4275, benzyl bromide:
      38.0       1.5
      39.0       5.6
      41.0       1.3
      50.0       2.1
      51.0       3.1
      52.0       1.4
      62.0       1.8
      63.0       5.0
      64.0       1.6
      65.0      12.2
      89.0       4.3
      90.0       2.5
      91.0     100.0
      92.0       8.0
     170.0       4.1
     172.0       4.0

with the first column about m/z, and the second about the relative intensity of peaks recorded which I save as file BnBr.dat.
Launching gnuplot (in Linux, this would be gnuplot) in the folder containing the data file to visualize, the minimal command within gnuplot's terminal would be
plot "BnBr.dat" with impulses

The then available window includes a magnifying glass, by right button mouse click and drag you can define the region of interest to magnify.  Note that simple hoovering of the mouse allows to read values of abcissa and ordinate, too.

If you invest yourself a little bit deeper into the syntax of gnuplot, you can write small scripts to reuse certain actions.  Let's assume you saved the following snippet as file example_script.gp
#!/usr/bin/gnuplot -c

set term png

output_a=ARG1
output_b=".png"
output_file=output_a.output_b

set output output_file

set grid
set xrange [20:*]
set yrange [0:100]
set xlabel "m/z"
set ylabel "intensity [%]"

plot ARG1 with impulses linewidth 2 title ARG1

then this utility can write you a permanent record (as .png file) when called in pattern of
gnuplot -c example_script.gp  BnBr.dat

to yield the static file BnBr.dat.png as lightly embellished overview:

(In case of Linux, you can provide the script the executable bit by chmod +x ./example_script.gp, to shorten subsequent calls to a pattern like ./example_script.gp BnBr.dat)  Not only that this script documents how the data were processed (and that this recipe can be shared/extended with colleagues), this allows you to consistently apply the same operation on stack of many MS data:

the flag -c instructs gnuplot to collect arguments from the command line, here: the file name containing the raw data
it defines png as output format (alternatives can be pdf, svg)
it constructs a file name for the permanent record to be written
as visual embellishments, an optional grid, labels on abscissa and ordinate, and explicit ranges of the axes: always the complete range (intensity scale), and to skip the display of fragments typically too light to be of diagnostic value for organic molecules (m/z scale)
eventually plot the diagram with wider lines

(Beside the material on gnuplot.info, the blog gnuplotting.org and Philip Janert's Gnuplot in Action are among valuable resources to gradually learn gnuplot.)
If your data are comma separated/.csv and you don't mind adding a header on each column, you can upload the file to a service like plotly chart studio.  This approach is more spread sheet/mouse click centred with interactive pan and zoom:

Addition:
Contrasting to UV-Vis, IR, and NMR with fix chromophores to absorb some radiation to yield a signal (perhaps it overlaps with a signal by an other), the fragmentation mechanism and hence pattern of the eventual recorded MS spectrum depends e.g. on the nature of ionization (hard EI vs the softer CI and MALDI technique).  This complicates the prediction of a complete MS spectra.
Nevertheless, rules derived from recorded spectra provide guidance which can be implemented into computer programs.  Among the MS toolbox by EPFL however are calculators like a mass calculator for small molecules (enter Hill formula, SMILES string, mol file, or structure formula) to provide a prediction which simultaneously considers the isotopic intensity pattern $\ce{^{12}C}$/$\ce{^{13}C}$ and e.g., $\ce{^{79}Br}$/$\ce{^{81}Br}$.  The pattern about the input structure can be downloaded as .svg or .csv:

This leaves it to the user to recognize in the molecule structures known to plausible fragmentation reactions ($\alpha$-cleavage of aryl ketones, McLafferty fragmentation, etc.) which seem to be implemented in the predictions by ChemDraw, or ChemSketch MS Fragmenter.
Within the project Competitive Fragmentation Modelling for Metabolite Identification (CFM-ID), there is a spectra prediction which, departing from SMILES or InChI

« ... predicts QToF MS/MS spectra for multiple collision energies for a given input small molecule. Spectra are computed for low (10 eV), medium (20 eV) and high (40 eV) collision energy levels and are represented by a list of 'mass intensity' pairs, each corresponding to a peak in the spectrum.»

along with a peak assignment (for experimentally recorded spectra) and compound identification.  With BrCc1ccccc1, a SMILES string to represent again benyzl bromide, two of the spectra of fragmentation pattern suggested are shown below:

Though you can access the results of the algorithm as pure text file and by pic of the peaks a suggested fragment (e.g., an isomer of the tropylium ion), differences between the suggestion for $\pu{20 eV}$ vs $\pu{40 eV}$ are noticeable.  However, though an ionization with $\pu{40 eV}$ here is considered high, it is low in comparison to frequently seen $\pu{70 eV}$ in routine LC-MS in the organic synthesis lab to yield as much as possible fragmentation of small molecules (the MS by AIST was recored with $\pu{75 eV}$).*  Your question does not detail if the data to analyze and compare with a reference actually are larger proteins/biomolecules, or not (perhaps BnBr is not representive for your analytes).
* In fairness to the algorithm however, a primary alkyl bromide is a nasty function unlikely to be present in a drug, nor metabolite.

Thank you for the very in-depth answer. I really appreciate the effort you've put into helping me solve my problem.
I've used Gnuplot in the past, so I knew that it had the capability to make nice looking plots of this data. But I'm a novice with the program, so this explanation is definitely valuable as I try to make better looking plots. Thank you!
However, the main functionality I'd like is simulated/theoretical peaks, ideally input with molecular formula. This way, I can quickly analyze messy spectra. I don't think I conveyed that very well in my original post. Thanks again.

@J.R. The answer was slightly extended.


text:
why does rate determining step lead to these inequality relations?

Here, the rate expression for the mechanism (i) is below:
$$rate = \frac{K_1^2k_2k_3[H^+][A]^2}{k_{-2}+K_1k_3[A]}$$
and for (ii),
$$rate = \frac{K_1k_2k_3[H^+][A]^2}{k_{-2}[H^+]+k_3[A]}$$
I was asked to show that the two sequences are kinetically distinguishable when the final step (i.e., C-C bond formation) is rate- limiting. The solution key says the final step being rate-limiting leads to the below expression. The rest is just some algebraic calculations which I don’t have a problem with, but I don’t understand how the below relationships are derived from the information on the rate-determining step. Could somebody kindly explain in details?
For (i),
$$K_1k_3[A] << K_{-2}$$
For (ii),
$$k_{-2}[H^+] >> k_3[A]$$

There is an error in the last row of the schema. Both neutral and protonated acetaldehyde are labeled the same and both reactions are assigned the same kinetic constant k3.

my bad, I have edited it. However, the question says that the last step's kinetic constant are both K3.

But they cannot be numerically the same.

When $k_3$ is v.v small wrt other constants then the limits shown apply, then the two schemes are distinguishable, but they are anyway so I don't see the point of the question.


text:
Isomers of Pentaaminechlorocobalt(III) chloride
What kind of isomers does $\ce{[Co(NH3)5Cl]Cl2}$ exhibit?
I can rule out geometrical and optical due to there being $\ce{5 NH3}$ ligands which central metal atom cannot have different positions of $\ce{Cl}$ because there exists only one.
This does not show linkage isomerism because there is no bidentate or polydentate ligand for that , this does not show coordination or solvent isomerism because of No coordination second complex and no solvent in the chemical formula
Does this show ionization isomerism , as $\ce{NH3}$  could occupy the position of $\ce{Cl}$ in the front and we could have $\ce{[Co(NH3)3Cl3](NH3)2}$ but I am confronted on whether amine could occupy a counter ion's position where the counter ion exists to balance charge , yet there is no change of oxidation state of metal and then this transition could occur freely ?

Chemistry SE  (in contrary to some other SE sites) strongly recommends plain text question titles for index/search reasons and due possible displaying issues in question title lists.

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But then the sum of charges does not fit.
Possible are these:  $\ce{[Co(NH3)6]Cl3}$, $\ce{[Co(NH3)5Cl]Cl2}$, $\ce{[Co(NH3)4Cl2]Cl}$, $\ce{[Co(NH3)3Cl3]}$.

can we have $\ce{Co(NH3)3Cl32}$

because Again for ionization isomerism , we get $\ce{2NH3}$as a product but , still not sure we can count this for ionization isomerism

How would be those 2 external NH3 bonded?

I am not sure @Poutnik , thats a very good question , I am just learning co-ordination compounds and my guess is that they are externally bounded just like the 2 chlorine atoms at the start bounded to the metal complex

Chlorides are ( in solid state) bound within ionic bond. That is not the case for ammonia. In solution is chloride and ammonia independent on the cationic or neutral complex . // Another thing could be ammonia solvates (analog to hydrates), but that may require liquid ammonia solvent.

Oh that makes sense!! The ligands give lone pair electrons , but counter ion is an ion and makes ionic bonds , which means $NH3$ cannot bond hence we can conclude this complex has no ionization Isomers !

then possibly it can be solvate isomerism @Poutnik


text:
Safety of an organic solvent in a sealed pressure pot or vacuum chamber
I am trying to experiment and find ways I can reuse various types of thermoplastics at home for hobby use and have investigated various solubilities of them in solvents (room temp or otherwise) to experiment with recasting in molds. One common issue with a mixture containing PolyStyrene is similar to casting of thermoset resins, trapped air bubbles (or even trapped solvent bubbles)resulting in pitted castings. So I was considering if it was possible to either degas the mixture by use of a vacuum chamber  during or before casting in addition to or in lieu a pressure pot like with thermoset. But my chemistry knowledge is limited to say the least whether this is safe or not.
Would the vacuum pump simply need to have solvent resistant fittings and/or a brushless motor to prevent ignition of vacuumed solvent vapors given off by the mixture?(ventilation would obviously be present
Likewise for a pressure pot, I assume whatever solvent evaporation that occurs would only continue until the air is totally saturated and then no further evaporation would occur ? And would just need to ensure proper ventilation when releasing the pressure in the chamber to avoid vapor build up in the immediate area?
Potential solvents used for the PS include Acetone,Toluene,THF,D-Limonene, a mixture from a dual cure (UV cure or mekp catalyst)polyester thermoset resin containing styrene monomer, or just styrene monomer.
Thanks for your time. Haven't been able to find any answers like this anywhere on the Internet.
Feel free to point out my stupidity if this is a dumb line of questions.

You'll never get the solven out of the melt, unless you first precipitate the PS by adding e.g. water or methanol. Save yourself a lot of trouble, and just melt the bulk plastic you want to recycle.

Trying to dissolve and reuse plastic as a hobby might not be a good idea.
There are considerable environmental, as well as safety, concerns. Releasing sizable amounts of organic solvents into the atmosphere, whether as effluent from the pump or just from evaporation, is against the law in many locales. There are contaminated locations such as Solvent Savers, a United State Superfund remediation site.
In addition, as you've mentioned, the solvents may be immediately toxic, and also present a fire hazard.
While wanting to recycle and reuse plastics is laudable, it should be done in a way that does not cause further harm. A large commercial operation might evaporate, condense and reuse solvent with an efficient counter-current heat exchanger, you're unlikely to do so at home.


text:
Does ammonia gas neutralise Hcl salt of amines in dry non polar medium
I am trying to basify/neutralise the $\ce{HCl}$ salt of amine and other organic compounds by bubbling dry(or semi dry) ammonia gas through a column of  the salt suspended in a non polar solvent like toluene or xylene.
Since there is little to no water present, will the ammonia gas be able to react with the Hcl to form ammonium chloride?

This is simply a bad idea. Do you know how dangerous NH3 gas is? Even as a hypothetical scenario it would be contrived.

I have lot of experience working with ammonia gas, is that the reason for all the downvotes? pen and paper chemists are running the show I guess nowadays.

Well, if you wanna risk your life instead of using things that are safer and work better, it's your call.

It heavily depends on the type of amine or organic compound you are using.
If you have chloride of primary, secondary or tertiary amine then it is going to be difficult because they are more basic than ammonia and would not easily lose $\ce{Cl^-}$.
If you are using aniline then ammonia can easily abstract $\ce{Cl^-}$ because it is less basic than ammonia.


text:
Validity of ideal gas law for pure species or mixture
I'm currently dealing with an application involving gases. I have pure nitrogen as a pressurizer and eventually water vapour (only if condition for evaporation or boiling are met).
I wanted to ask to which extent can I consider pure species or mixture as ideal gases. I know that nitrogen reaches critical condition when pressure is about 33 bar. My application would have initially a small amount of nitrogen pressurized at 17 bar approximately.
Is it better to switch to a cubic equation of state like the Peng - Robinson one? Would that justify the additional complexity with respect to the ideal case?

Why won't you calculate a few points both ways and see how big the difference is?

Yep @Ivan Neretin, I'm structuring the code for computation in the ideal case for which computation is straight but dealing with real gas has to consider another level of complexity if dealing with different equation. I will try as you suggested ;)

Nitrogen  crit. conditions are  -147 deg C + 34 atm.

Thanks @Poutnik, i think i won't exceed over the critical range since nitrogen will remain in gaseous state.

At room temp. you'd have to go much further than 34 atm. for N2 to be something different than just a compressed gas. Than again a compressed gas isn't necessarily all that ideal. Maybe start with van der Waals.


text:
Can you give an example of an electrolytic process that has high Faraday efficiency but low energy effiency
I want a nice example to help illustrate the conceptual difference between these terms to a biologist.
I found this figure which might be helpful.https://www.researchgate.net/publication/343879093_SAPHYS_Project_-Development_and_Testing_of_a_Stand-Alone_Photovoltaic_HYdrogen_energy_System-_Final_Report

Could I give an example of a biological system that perfect transfers electrons between different donor/acceptors where the initial donor has high redox potential and the terminal acceptor has low redox potential. Then there is 100% Faradaic effeciency, but low energy efficiency.
Thank your for your support.


text:
How do I interpret the results of this DNA gel electrophoresis performed with potentially mislabeled samples?
Here is the cropped image I am working with:

It doesn't really matter for my question, but this was performed with 0.8% agarose gel in 1xTBE buffer using ethidium bromide and a TriDye 1kb DNA ladder, run at 100V, 200 mA for 45 mins.
I am new to DNA electrophoresis so I am still learning how everything works. I understand that the  DNA migrates a distance inversely proportional to the log of its molecular weight, and also based on the conformation it takes (closed circular, open circular, linear, etc.)
This run was meant to be a sort of mock-forensics experiment. There is DNA from the "crime scene", "suspect 1", and "suspect 2". There are 3 samples from each, one is untreated, one is digested with EcoRV, and one is digested with PstI. I thought for certain I knew the order of the samples (which were provided but simply labeled 1 - 9), but I am starting to have second thoughts. Based on the information I was given I am unsure how to interpret what is going on with each set of bands, especially since I am now doubting which sample is which. One of the goals besides empirically analyzing the data is to determine which suspect committed the crime, but after consideration I believe I am either missing something, or misunderstood the sample order.
Here is the information I have regarding the samples, as per the procedure I was following:

You will be given 9 samples for the separation and analyses. A specific region of DNA from
each of the three samples (Crime scene, Suspect 1, and Suspect 2) were prepared by

Isolated and incorporated into plasmid (circular form) - untreated
Above mentioned plasmid was cleaved at the specific DNA sequence motifs – treated 1 & 2

Later, they are listed as:

Samples
Crime scene (Untreated and treated)
Suspect 1 (Untreated and treated)
Suspect 2 (Untreated and treated)

Given this information and lack of contradiction during the procedure, I assumed that the samples labeled 1 - 9 corresponded to

Crime Scene - untreated
Crime Scene - EcoRV
Crime Scene - PstI
Suspect 1 - untreated
Suspect 1 - EcoRV
.
.
.

As instructed by the procedure, I am 99% sure that sample 1 was placed in the well next to the ladder, and then 2 - 9 followed sequentially to the right. So samples 1-9 should be placed in wells 2-10. I only leave room for doubt as I am trying to figure out what is going on.
Moving on to the gel itself, the double banding patterns on wells 5, 8, 9, and 10 appear almost identical to what I have seen of a mixture of oc and ccc forms after plasmid prep. This is what I would guess the untreated samples should look like, assuming they were prepared in that way. All I know of how they were prepared is in the line "Isolated and incorporated into plasmid (circular form)" from the procedure. Even so, I have had no indication that the untreated samples would be grouped together, or that they would be samples 7, 8, and 9. I guess anything is possible at this point though.
It was my understanding that digestion with a restriction enzyme causes a break in both strands leading to exclusively linear form. Linear form should travel less distance than the ccc form, but more distance than the oc form. So even assuming I got the samples completely mixed up and 8, 9, 10 are the untreated samples, I don't see how the rest of them could be a result of being linearized.
I also have no idea how to make sense of the three bands in well 2, I haven't learned anything that would explain that given what was supposed to happen. I actually don't have any idea how to make sense of the whole first set of samples (#'s 2, 3 ,4) seeing as all of their bands are significantly lower than every other band on the gel.
Sorry for the wall of text, I am just very confused as to how to piece this all together. What could describe the patterns shown given the context I provided?

You would think that the plasmid of suspect 1 and 2 is about the same size (or exactly the same size), and that the plasmid found at the crime scene is identical in length and sequence to one or the other. Finally, we have to assume that the DNA of the two suspects are different from one another.
Lanes 5-10 look like undigested plasmid and carry little information.

[OP] It was my understanding that digestion with a restriction enzyme causes a break in both strands leading to exclusively linear form. Linear form should travel less distance than the cc form, but more distance than the oc form.

The restriction enzymes cut both strands. If there is one site on the plasmid, it gets linearized and you can measure the size of it. If there is more than one site, the plasmid gets fragmented. The sum of the fragment sizes should match the total size (here are some examples). There is no example of a full-size linearized plasmid on this gel, so no bands between cc and oc form of the plasmid in this example.

[OP] I also have no idea how to make sense of the three bands in well 2, I haven't learned anything that would explain that given what was supposed to happen. I actually don't have any idea how to make sense of the whole first set of samples (#'s 2, 3 ,4) seeing as all of their bands are significantly lower than every other band on the gel.

Lanes 2, 3 and 4 look like digested plasmid, cut either twice (two fragments) or three times (three fragments). The fragments add up to about 5 kB, typical for a plasmid. Lanes 3 and 4 are identical, and lane 2 is different (with an extra restriction site). I would guess these are suspect 1, suspect 2 and crime scene sample digested with the same enzyme.
Bottom line
If this is a commercial kit, give them a call to clarify. This answer is only an explanation of the principles.

That helped fill in some blanks, thanks. I think I may have got it, the sets of samples might be grouped by treatment, the treatment order is reversed, and within each treatment grouping the suspect order is reversed from what I originally assumed. where 10 is untreated crime scene, 9 is untreated suspect 1, 8 is untreated suspect 2, and then in that order for the treatments as well in the following groups of 3. But if that were the case, wouldn't lane 6 and 7 be full size linear? They are between the oc and ccc of 9 and 10 and collapse into a single band, otherwise I'm not sure what that is.

@Sidereus Grouping by treatment, with the crime scene between the two suspects, would make comparisons easier. Especially when the gel does not run straight.

Sometimes you don’t see the faint second band for intact plasmid.