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Confusion with definitions of mass
What is the difference between:
atomic mass
relative atomic weight
relative isotopic weight
standard atomic weight
atomic weight
relative atomic mass
I am told by Wikipedia that:
relative atomic weight = atomic weight
and a the start of the article it says:
For a single given sample, the relative atomic mass of a given element is the weighted arithmetic mean of the masses of the individual atoms (including their isotopes)
so standard atomic weight = relative atomic weight
But at https://en.wikipedia.org/wiki/Relative_atomic_mass#Standard_atomic_weight#Definition it says:
It is a synonym for atomic weight, though it is not to be confused with relative isotopic mass. Relative atomic mass is also frequently used as a synonym for standard atomic weight and these quantities may have overlapping values if the relative atomic mass used is that for an element from Earth under defined conditions. However, relative atomic mass (atomic weight) is still technically distinct from standard atomic weight because of its application only to the atoms obtained from a single sample; \textbf{it is also not restricted to terrestrial samples, whereas standard atomic weight averages multiple samples but only from terrestrial sources}
I am told here that:
The standard atomic weight (Ar, standard) of a chemical element is the weighted arithmetic mean of the relative atomic masses (Ar) of all isotopes of that element weighted by each isotope's abundance on Earth.
But in this video I am told this is the definition of relative atomic mass.
Here I am told:
Atomic mass (ma) is the mass of an atom. A single atom has a set number of protons and neutrons, so the mass is unequivocal (won't change) and is the sum of the number of protons and neutrons in the atom.
Atomic weight is a weighted average of the mass of all the atoms of an element, based on the abundance of isotopes. The atomic weight can change because it depends on our understanding of how much of each isotope of an element exists.
In other words:
Atomic weight = standard atomic weight
Also, which of these definitions is used to convert grams of a substance into moles

Related: Quick and simple explanation of molar mass, molecular mass and atomic mass

I have a bad feeling that the terminology is not properly standardised and that chemists are terminologically confused. However, this may not matter much in practice as the specific meaning is almost always obvious from context. I'm happy to be proved wrong, though.

https://chemistry.stackexchange.com/questions/38082/what-is-the-difference-between-molecular-mass-average-atomic-mass-and-mola

@matt_black, I agree that the way atomic masses or atomic weights are taught in general  chemistry is very confusing and superficial.

Thanks these websites clear some of the ambiguity

Relative Atomic Mass vs Atomic Weight
Relative Atomic mass ($m_a$) is the measurement of the mass of an atom relative to carbon-12. It's dimension is M.[1] It can be measured in Da/u, kg or g.* [3]
$$m_a \approx \mathrm{Mass\ Number} \times {1\ \mathrm{u}}$$
except for carbon-12 where they are the same.
Atomic weight is:
Relative atomic mass vs Standard atomic mass
Relative atomic mass or Relative atomic weight is the weighted average of the isotopes of an element according to their abundance in a given sample compared to the atomic mass of carbon-12. It's dimension is M/M or 1. [2] [4]
Standard atomic mass is the same except that the samples are restricted to terrestrial samples normally considering/averaging results from many different samples or results given by the CIAAW.
Relative Isotopic Mass vs Relative Atomic Mass
Relative Isotopic mass considers the mass of an isotope compared to the atomic mass of carbon-12. This is also dimensionless.
*Universal mass constant vs kg , g ,etc
The universal mass constant ($m_u$) is defined as $\frac{1}{12}$ of the mass of carbon-12 which defines 1 Da or 1 u. All measurements in Da are comparisons to the mass of a carbon-12 atom. Since the discovery of Avogadro's constant, we know: [3]
$$ 1\ {\rm{Da}} = 1.660\ 539\ 066\ 60(50)\times 10^{-27}\ \mathrm{kg}$$
Molar Mass vs Molecular Mass (or Formula Mass)
Molar Mass is the grams of a substance in 1 mole of it measured in gram per mole. It's dimension is $\mathbf{M N^{-1}}$.
Molecular mass or molecular weight is the sum of the atomic masses of all the component atoms of each element measured in u. It's dimension is M. Formula mass or formula weight is the sum of the atomic masses of component ions (not sure of the difference between this and molecular mass - in terms of quantity).[2]
[1] see the answer to this Q by M Farooq
[2] What is the difference between "molecular mass", "average atomic mass" and "molar mass"?
[3] Mass number, (relative) atomic mass, average mass
[4] Quick and simple explanation of molar mass, molecular mass and atomic mass

If you are confused, it is not a surprise because chemists remained confused for 200 hundred years. Welcome to the world of real science.
Atomic weight is the older term for atomic mass. Modern day hair splitters would say that mass and weight are different things but historically in the old chemical literature, they meant one and the same thing.
Nobody can repeat two centuries of work here, but briefly, atomic mass of an element meant that it is the mass of any atom that combines with the mass of one oxygen atom.
Now the key question is which leads to opening the Pandora box. What is the mass of one oxygen atom? People had to choose a number, because nobody knew the mass of oxygen atom. Some said, let us fix it to 200, some fixed it to some other number. This arbitrary "mass" of oxygen atom kept on changing, finally, someone said, let us fix it exactly to 16.000000000... (ad infinitum) units.
Notice that I did not need any crutches of moles or grams per mole. This is all modern day stories fed to fresh minds. We are still in early 1920s.
Now once the mass of oxygen is fixed, you can relatively easily assign an atomic weight of other elements with respect to oxygen
For example, atomic mass of hydrogen was determined to be 1.008 which is the mass which would combine with exactly 16 units of oxygen.
Now you can understand that chemists never  talk about absolute atomic masses, they are all relative to some element, so it is relative atomic mass.
Today, the reference is carbon-12 (after 1960s) and there are many more nuances which may not be of interest at this moment.
Think of relative atomic weights like this. Suppose I want to assign an "atomic mass" to you, but I do not know your mass. However, I know your friend's mass which is arbitrarily assigned as 100 lb. Using your friend as a reference we can assign an atomic mass to you indicating whether you are heavier or lighter than your friend.


text:
Can you steam clean your range hood, by adding dishwashing liquid to boiling distilled water?
My grandparents physically can't remove their Sakura R-727II range hood that lacks any filter. Because of COVID-19, no handyperson can visit their house. But their range hood is now clogged and failing to suck out fumes, so they must de-grease their range hood's interior that hasn't been cleaned in 4 years.
Please see the pictures below. They wonder if they can de-oil their range hood by adding dishwashing liquid to boiling distilled water, then boil this mixture to evaporate the dishwashing liquid that will rise into and de-grease their range hood.

Does the dishwashing liquid vaporize as they think? Or does it remain in the saucier?

Can the resultant evaporated dishwashing liquid + steam combination de-grease their range hood? I wonder if this dishwashing liquid + steam will have enough pressure.

The two pictures above are like their range hood. Theirs isn't a Samsung range hood pictured below, but I used it to devise my collage for it shows steam.

This is not going to work.

Dishwashing liquid cannot be evaporated. It cannot work. It should not be suggested. Wait for a professional service.

There must be a way to remove and exchange the filter from the hood, if not, the thing has been worthless from the very start.

What is that nonsense that no handyman can visit their home? Just stay outside while the man is at work.

@Martin-マーチン Please see the second picture that I just added.

You see the screws in front of the fans? And, next to the rectangular lamp? And, isn't there an instruction manual for this hood available, at least on the site of the manufacturer, with a point regarding the maintenance of the hood, too? E.g., for https://www.bosch-home.com/us/productslist/cooking-baking/ventilation/island-hoods/HIB82651UC#/Tabs=tab-3324792/ there is page 9 in this .pdf: https://media3.bosch-home.com/Documents/9001126905_A.pdf

This does not look like a 4 year old range hood that has never been cleaned. Where does it exhaust to? Maybe there is a problem on that end. According to Samsung, you can remove the stainless steel baffle "filter' and put it in the dishwasher (seems to be removed in OP's second picture).

https://chemistry.stackexchange.com/questions/137073/can-you-steam-clean-your-range-hood-by-adding-dishwashing-liquid-to-boiling-distilled-water

@KarstenTheis Sorry for the confusion. Theirs is the Sakura R-727II, not the Samsung. I edited my post.

@Buttonwood Sorry for the confusion. Theirs is the Sakura R-727II, not the Samsung. I edited my post.

There is a related discussion on https://diy.stackexchange.com/questions/185676/how-remove-sakura-r-727ii-to-clean-inside

@Accounting The indicator to one of the hoods by Bosch was only a non-specific example; in part because of their push into the branch of «smart home» and «internet of things» (e.g., https://www.youtube.com/watch?v=v2kV6pgJxuo, or https://www.youtube.com/watch?v=pCoy77P-JmY (heater in the US with Celsius scale!),  a milder version https://www.youtube.com/watch?v=aSZM2iYgrfg), and in part of later surprise such hoods (now) include a WiFi interface (e.g., https://www.youtube.com/watch?v=BdPaG2W5xSU), too.  Well, not sure if their slogan «live like a Bosch» equally is used e.g., in France ...

Clogged? Failing to suck out fumes? Quantitatively, how bad is it? And in what manner did this situation arise? Slowly, over time? Or suddenly? Can you hear a fan running?
Grease has a high boiling point, and while it is theoretically possible to clog some fine filter, it is doubtful that 4 years of home cooking could stop a hood fan from operating. In commercial practice, hoods over grills are cleaned frequently from spattered grease, not so much for better air flow, but more for sanitation and prevention of possible fires from leaping flames.
If no filter is accessible from the stove end, perhaps the exit end is the cause for blockage. Exit openings frequently have flaps to prevent rain entry. Two possibilities: 1) the flap is stuck down and hinders airflow, or 2) the flap is stuck up and the tube is blocked by a bird nest or a pile of acorns. (Of course, this exit end will be so high that it is not accessible for cleaning, but that's another problem.)
There is a third situation. In my former house, the builders omitted an outdoor exit pipe for the microwave and fume hood. There was simply a fan which sucked the steam/vapor up off the stove, thru the filter and back at the cook. We generally turned the fan off. The idea of a fume hood was nice, but not really necessary.

Any time a piece of equipment goes down, you cannot get a repair person, and you are not sure what to do, try to call or email the manufacturer. This is the US contact information for Sakura.  They know their product better than anyone on this site and will probably know about common issues.
Steam will loosen, but will not get hot enough on a stove to remove grease. The only safe way to remove grease is to get long gloves and scrub it.
Have you ever seen the mess dish liquid makes when put in a dishwasher?  The results of what is suggested more likely transport the soap all over the counter-tops instead of to the grease.

I like this answer. It's like: Read the directions first. If you don't have a manual, contact the company for directions. Maybe there is a fault that they will compensate you for. Only then should you do it yourself (if there is no official help available).

First off, let's clarify something:
When you boil water in a pot, hoping to carry whatever is dissolved within the pot in the steam, that thing should have a lower or the same boiling point as water (100 ℃).
A possible slution:
As grease and other fats gets carried up into the hood it usually cools down and the polymerizes and gets denser and harder to remove. You could, however, heat up the grease and fats again by using either a steam-cleaner or boiling some water very close to the hood for a couple of hours. The heat will "soften" up the grease thus leading it to eventually loosen the hood. (ONLY TURN ON THE HOOD ON THE LOWEST SETTING TO GUIDE THE VAPOR INTO THE GREASE - A higher setting will suck the grease further into the hood).
When the heating is done, you should be able to remove the hood fairly easily without the grease holding anything into place as it is more or less "melted".

There is a way to achieve a result strictly within the bounds of your question, but it's just as insane as these bounds.
Boil a solvent, not dishwashing liquid.
Say, gasoline. Or much better dichloromethane (sold as paint remover), if there is not much
plastic at the kitchen.
Don't turn fans on. Hood must act like reflux condenser. Let dichloromethane fumes condense inside, flow through it and drip.
Needless to say, it's a way to turn the kitchen into hell and is completely insane for health and fire danger :)

By the way, you couldn't boil the dishwashing liquid because of the huge amount of foam :)

Are you out of your mind? You suggest someone to boil dichloromethane in his kitchen. While you briefly point out the health hazards, I still don't think that justifies that answer. You don't know how well the questioner, or other people who read this thread, can assess the dangers of such an undertaking. This answer is really reckless!

I strongly believe that any filtering of knowledge is evil.
My answer is pretty anecdotal, but demonstrates probably the only way to remove polymerized clogging "remotely".

Instead of boiling CH2Cl2, which probably wouldn't condense in the filter because the vapor would be diluted with too much air, or wouldn't even get into the filter if there is NO air flow, consider a safer method: squirt it in with a garden sprayer. This is safer because it  would use less CH2Cl2 and direct it more toward the problem. But then, go even safer: squirt dishwashing solution instead of CH2Cl2. Put a big pan on the stove to collect drippings. Color the liquid with food color to see where it leaks into the house - or where it exits outside.

Solvent will work (if you manage to spray it inside), but not dishwashing solution

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Stereo-isomerism in 7-methylbicyclo[2.2.1]hept-2-ene

The above are two compounds.

The objective is to find if the compounds are identical/enantiomers/diastereomers

I can see a plane of symmetry if we keep the $\ce{H-C-CH3}$ in the plane. So, concluding it as identical looks great.
but, if so, how can one transform the first compound to the second?

Applying, CIP rules, we might invalidate the P.O.S. The solution given for this question is "identical".
Update:(attempt)
I have somehow manipulated the bonds such that I can prove the identity. Even though it is extremely-sterically hindered as indicated in the comments section (Now moved to chat). The forceful manipulations are done keeping in mind, not to break any bonds and only .

However this again proves that the molecules are not identical.
Now, since it is proposed that these molecules are different, can I get a lab or computer synthesized version of both molecules? Upon many search attempts, I could get this document which discusses about the same cyclohexene ring but Deuterium instead of the $\ce{CH3}$ at the bridge head and substituted oxygen ions.

Comments are not for extended discussion; this conversation has been moved to chat.

7-Methylbicyclo[2.2.1]hex-2-ene exists as two diastereomers, anti-1 and syn-1, which differ by the relationship of the methyl group and the double bond. Both compounds are meso with the bridgehead carbons stereogenic and chirotopic (R/S) while C7 is stereogenic but achirotopic (r/s). The plane of symmetry  in each one does not produce an enantiomer of itself. Stereoisomers have the same molecular formula and the same atom connectivity. You probably know that the stereoisomers (R,R)- and (S,S)-tartaric acid are enantiomers and bear a diastereomeric relationship with (R,S)-tartaric acid, which is a meso-compound. A pair of meso-compounds with the same molecular formula and the same atom connectivity may also be diastereomers. Just like structures 1, the central carbons (C3) of ribitol and xylitol are stereogenic and achirotopic. The properties of these two pentaols are different as are the properties of anti-1 and syn-1.

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Are there methods for iron content determination in spinach that do not require thiocyanate?
I am looking for a way to measure the iron content of spinach for a chemistry experiment. Unfortunately I am not sure that thiocyanate will be available and I'm therefore trying to find an alternate method. The most common one seem to be a titration with potassium permanganate. The issue with this method is that other much more abundant metals in spinach would also react with the permanganate.
I had the idea to ash the spinach, dissolve the ashes in water. Then use a displacement reaction since iron is the least reactive metal in the chemical makeup of spinach. I am not sure exactly how but I thought it might be possible to use a compound to precipitate the more reactive ions out of solutions.
Do any of you have some ideas regarding this experiment?

I suppose you need to dissolve ash in acid, otherwise iron could end as insoluble oxides ( or metal if highly heated with carbonized organics ). The iron oxidation state after dissolution can be uncertain, as oxides tend to be non-stoichiometric and reducting environment during burning undefined.

Through spectrometer: https://chemistry.stackexchange.com/questions/18435/how-to-determine-the-iron-content-in-spinach-with-a-spectrometer?r=SearchResults

Or through titration: https://chemistry.stackexchange.com/questions/42866/how-to-determine-the-iron-content-in-spinach-from-a-titration-with-permanganate?r=SearchResults

@NilayGhosh yes I am looking for a method other than the spectrometer since I may not have access to KSCN. The problem with that titration is that many other metals will react with the permanganate.

@Poutnik How could I proceed from them to determine the amount of iron in the solution?

Hm, with avoiding instrumental techniques ,including spectrometers, it would be difficult, as manganometry may not be specific enough. But anyway, only about 2% of spinach iron ( 2-2.7 mg/100g) would be available for a body, as it is mostly blocked by oxalate, compared to 15-35% by meat sources, where iron is mostly bond in the heme.

@Poutnik I thought oxalate could be "broken down" by cooking/ashing? Yeah manganometry seems like it would be imprecise since so many other metals would react with the manganate. Thats why I was thinking of using another compound before the manganate to precipitate all the iron out of the ash solution, given iron is one of the least reactive metals in spinach. Do you think there would be a way to do this?

I have read oxalate content drops by spinach cooking from 1000mg/100g to one half.

Spinach is not specially rich in iron. $100$ g spinach contains $3.1$ mg Fe. $100$ g beans contains $6.1$ mg Fe. Lentils  $8.6$ mg/$100$ g.. Soja$ 8.4$ mg/$100$ g. Nutmegs $4.5$ mg/$100$ g.   Ref.: K. Diem. C. Lentner, Tables scientifiques, CIBA-Geigy SA, Basel, Switzerland, $1972$, p. $511 - 515$.

$100$ g fresh spinach contains $662$ mg $\ce{K}$, $106$ mg $\ce{Ca}$,  $65$ mg $\ce{Cl}$, $62$ mg $\ce{Na}$ , $62$ mg $\ce{Mg}$, $51$ mg $\ce{P}$, $27$ mg $\ce{S}$, $3.1$ mg $\ce{Fe}$, $0.82$ mg $\ce{Mn}$, $0.2$ mg $\ce{Cu}$. From the same reference as in my previous message.

Don't go reinventing the wheel, there are literature values for the iron contents of vegetables, and that literature comes with procedures how they were determined.

@Karl I understand, but my means are more limited

@ Hugo. Iron(III) can be titrated by EDTA $0.02$ M at pH$ 2.5$ and $45$°C. The indicator is thiosalicylic acid, which goes from red to colorless. If you can obtain this indicator, I will give you the detailed process. 1 mL EDTA $0.02$ M corresponds to $1.2$ mg Fe. This fits your needs. Ca and Mg do not disturb. Titration of Fe(II) can be done by KMnO4, but the iron must first be reduced by a Walden column (metallic silver). I also may give you the process, if you have got such a column.

@Maurice, What reference book do you have? It seems to have a lot of classical analyses.

@ Farooq. You are right. My reference book contains more than one hundred inorganic titrations with EDTA. It is a wonderful booklet called "Méthodes d'analyses complexométriques avec l'EDTA", 116 p., edited by Merck, Darmstadt, 1973. Unfortunately it is written in French.

@Maurice Any change you could send me a picture of that specific titration? My first language is French so that won't be a problem.

@ Hugo. I don't know how to add a picture to my message. So I copy the titration here. The sample can contain up to $35$ mg Fe. Dilute it up to $100$ mL. Adjust the pH to about $2.5$ with $\ce{NaOH}$ or $\ce{HCl}$ $ 0.1$ M. Check with indicator paper pH $0-6$. Add $1$ mL indicator ($5$ g sulfo-$5$-salicylic acid in $95$ g water). Heat to $45$°C and titrate the red solution with $\ce{Na2EDTA}$ $0.02$ M up to discoloration. This method gives only Fe(III). If the total iron content $\ce{Fe(II) + Fe(III)}$ is to be determined, the sample must be heated to boiling with $1$ mL conc. nitric acid.

@Maurice Merci beaucoup

I've used the ferrozine method before.  This review gives three different methods, one of which is the ferrozine method, and at a first glance, none of them require thiocyanate.  https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lom.2013.11.113

There are iron testing kits in water which are available at an affordable price. I have not used them but read more about them here Testing iron in well water. You can test your spinach extracts for a yes no type answer if iron is present in significant quantities or not. Just keep in mind that PopEye's spinach is really not that rich in iron. Too much iron is a liver toxin.
I am afraid to share the bad news for you that with the resources you have, you cannot reliably determine iron content in spinach. Micronutrients or minerals cannot be determined by classical methods because they are present in a complex matrix and in very small quantities (parts per million range). They need instrumental analysis (absorption by molecular complexes, atomic emission or atomic absorption). I saw a couple of papers from ResearchGate which talk about the titration of spinach extract with permanganate. Nothing can be more wrong than this procedure in analytical chemistry. They are basically titrating all the organic stuff with it. Those methods are horribly wrong. Someone on SE Chemistry posted a query on how to determine iron in spinach by titration Iron in spinach...that is all incorrect. Yes, you will generate some numbers with those burette readings but those numbers have no significance.
Regarding your ashing method, that will not work either, because you need at several kgs of spinach to get a small amount (milligram) of iron. What should be the ashing temperature? How would you isolate iron from the ashes? Selective precipitation to get rid of other minerals? Nope, that is a bigger headache. For that you would need more reagents.
If this is a school project, make sure you have the resources after searching the literature. If this is an home experiment- classical methods will not work.

As you are looking for inventive ways to possibly measure Fe presence for a school presentation, may I suggest a crude (but likely interesting) visual aid in possibly determining relative iron concentration.
One idea is that Fe ions in the presence of acidic H2O2 will engage in radical production. The latter reaction in the presence of suitable light over time could result in a cyclic reaction system (for example, photo-Fenton). The latter is a conceivable path to magnify even small transition metals presence.
The latter radicals (especially, the powerful hydroxyl radical) can breakdown organic matter, including, for example, a strongly colored dye over time, resulting in eventual de-colorization. The relative periodic time evolution for the latter could be a manner to simply display/document apparent differences in even small relative iron (also copper, manganese,..) concentrations.
Here is a citation from the literature as an example, Effect of iron salt on the color removal of water containing the azo-dye reactive blue 69 using photo-assisted Fe(II)/H2O2 and Fe(III)/H2O2 systems.
So, spinach grown in iron-rich soil, reduced to ash added to acidic H2O2 (plus perhaps more acid added 1st to the spinach,  further lowering pH) in the presence of a photo-sensitive dye subject to photolysis, should display more rapid de-colorization (as captured by periodic snapshots) than one grown in iron-poor soil.
You may experiment with various ways of numerically quantifying the tentative iron content, as deemed viable given limited resources (including funds which alternatively, could purchase an iron testing kit, available here, for example, at $99, or less expensive water testing strips here).
Note: I am assuming one does not have the time to actually grow the same variety of spinach. Otherwise, I would simply speculate that iron-richer spinach may possess different coloration (and perhaps other discernable quantifiable attributes) for the purpose of a simple relative classification as to iron content.
This would conceptually be based, relatedly to above, on naturally occurring photosynthesis. To quote from a supporting source:

Iron, one of the structural elements of organic components that play an essential role in photosynthesis and nitrogen assimilation of plants, is available at extremely low concentrations in large parts of the Southern Ocean's surface waters. We tested the hypothesis that photosynthesis is the primary target of iron stress in phytoplankton living in this specific environment, resulting in a reduced carbohydrate production.

On the suggested coloration argument relating to iron content, also a confirming reference, to quote:

Leafy vegetables featuring a deep, dark green color, such as spinach and collard greens, are usually high in iron.


text:
Comparing reactivity of 1-chloroethane and 1-chloropropane in an SN1 reaction
Beginning with a reference to a well known question.

Order by reactivity towards SN1 reaction.

According to some facts about SN1 reactions, rate depends on:

Stability of carbocations
Better leaving groups
Electron donation

If we consider point $1$, this rounds down the above question to a previously asked question.

Unfortunately the second answer to the above question raises doubt about the validity of the first in all cases. (The kinetic and thermodynamic stability)
Since my question is a bit different and asks about SN1 reaction I would propose considering the following:

The number of $\alpha$ hydrogen in the first compound is one more than the second.
The inductive effect of the ethyl group on the carbocation formed at the second compound is more than at the first.
Using hyperconjugation mechanics, we say that when the $\ce{H}$ atom is aligned with the Carbocation's $\mathrm p$-orbital, proper donation of electron takes place.

(So even though both compounds have unequal number of $\alpha$ hydrogen, the stability effect would be same?)
Since the hyperconjugative effect failed me, I would resort to orbital analysis and induction. An explanation of this point is given below.

Explanation for point $4$:
Since the C+ structure resemble the following :

We can say that the $\%s$ character of $\ce{^+C-C}$ bond in both compounds will increase. In turn the effective p character along $\ce{C-C+}$ would increase. This would imply that the $\%\mathrm s$ character of $\ce{C-H}$ bonds and $\ce{C-C}$ bond (in case of the second compound) will increase. We know that the size of carbon would be $\equiv$ to itself, so increasing the $\%\mathrm s$ more along $\ce{C-C}$ would be a great idea. This would imply that the $\mathrm p$ character of $\ce{C-H}$ bonds would be greater in the case of the second compound relative to the first, implying more donation effect.

So, to sum up my question, considering the above points can I say that the rate of reactivity towards SN1 will be greater for the second compound, i.e. $\ce{C3H7Cl}$?
Opposition or Alliance if also supported by experimental evidence would be more helpful.

Additional recurrence in the form of questions in tests or books:

A variation of the above question has also been asked in a national level entrance exam, JEE MAINS 2020, 4 September, Second shift. (Only instead of specifying Sn1, there was a reagent namely $\ce{HI}$).

The question is as follows, the objective being to find product B:

GRB Organic chemistry by Himanshu Pandey, Chapter: Halides, question number 66 to 76

I'm afraid you just wasted 100 rep. Why? First, that's another question hitting the wall of usability of various "rules of thumb" like inductive effect. Second, that's hardly experimentally verifiable because these compounds react via SN2 not SN1.

@Mithoron Firstly, I never said to use the thumb rule! (perhaps not clear, but now it is) Secondly, I said experimental evidence is appreciated ...that doesn't mean it is necessary for a post to qualify as the answer, third, I would've made it even greater if I had the rep. Also, why do you say these compounds react solely via SN2

Well, one important thing is SN isn't, in general, purely SN1 or SN2 and there's lots of things influencing that. If you conducted the reaction in such ways that it was more of of SN1, results would still vary depending on case. BTW, what is the meaning of last sentence in this post?

@Mithoron yes I am aware that it won't be a pure SN1. But, how would the result vary depending on the case, both are  apparently small. Last sentence in the post about "alliance and opposition" is in reference to my way of the justification using point 4. If it were a question about C+ stability, what would you have said(which is more stable)?

Did you looked at the solution, it says it'll proceed through SN2 pathway. It is due to the fact that degree of initial carbocations formed by cleavage of HI are comparable.

Okay, I got my fault. The second step is indeed dehydration. But, still I would say that it is unrelated to your question, as the first step happens through SN2 pathway, and not SN1.

@RahulVerma Please do not tamper questions without a rigid proof. see here

Hey, I didn't intent to tamper your question. Instead, I was trying to improve it by removing the unrelated ref. That referred question is indeed cleavage by HI, but the pathway is SN2. Also, the link you mentioned vague too (for the question).

To make things clear, 1) I'm following MOC for a long time. 2) I'd said that "pathway is SN2" specifically for the referred question, not in general. Finally, arguing is also a part of science, don't feel frustrated, take a deep breath and enjoy CSX ;) Yo!

I am not sure I understand this correctly, but is the reason your question for below 3. the idea that at a time only one H can be donating its electrons using hyperconjugation? If it's the case, the problem should be resolved considering molecules have so much energy,rapid rotation is always occurring about these c-c bonds, the ch3 is like a ceiling fan whose α H spend small amounts of time one at a time helping, so having 2 α H means less time receiving electrons so lesser stability. Having an extra α H is so beneficial, that the orbital character ideas you mention pale before it.

Consider the following assumptions to somehow force these substrates to proceed for $\ce{S_N1}$ reaction mechanism:

Low temperature

Polar protic solvent

Low concentration of nucleophile w.r.t. reactant

Now, in an $\ce{S_N1}$ reaction, the formation of carbocation is must.
The primary factor that determines the reactivity of organic substrates in an $\ce{S_N1}$
reaction is the relative stability of the carbocation that is formed.$\ce{^1}$
According to your linked question: 1-propyl cation would likely be more stable than the ethyl cation.
Hence, your deduction that "the rate of reactivity towards $\ce{S_N1}$ will be greater for the second compound, i.e. $\ce{C3H7Cl}$" is correct.
P.S.: The 1-propyl cation can rearrange itself to a more stable 2$\pu{^o}$ carbocation, but that is not part of RDS to decide the reactivity order.
Reference

Solomons, Fryhle, Snyder, 12E, Page 264

You avoided all of my question and bounty description. I specifically asked about checking the 4. th step, and also, the second answer on that link contradicts your claim thermodynamically. How did you check the relative stability, that is the question.

@IamAlita (1) I concentrated on your question, not what asked in JEE paper recently. (2) The answers on the link compares purely the stability of carbocations with no consideration of any reaction. And propylium is more stable than ethylium, thermodynamically. But here, we cannot consider possible rearrangements of carbocation (as mentioned in 'P.S.'). (3) In your 4th point, you are unnecessary making a simple thing complicated. (4) This is not a practical question and theoretically also won't lead to  anything.

Did you check if my reasoning applies to other questions as well? Of course you didnt considering the last line of the above comments.If you'd please, check GRB Advanced problems in Organic Chemistry(main and advanced), --> Halides, question 66 to 76. quoting propylium is more stable than ethylium, thermodynamically , how would you conclude such a thing in a competitive exam or a series of 10 questions with least access to such "experimental material" which is not practical?  The P.S. part would be unnecessary because I am not considering rearrangements, just given a race between two ---

Which of the participants will be finished off first. Also, if I had to eat the linked answer raw, I would not have created a question which supplies my logic, either you disprove it using a counter statement or an experiment.


text:
Why is 1,2,3,4,5,8-hexahydronaphthalene more stable than 1,4,4a,5,8,8a-hexahydronaphthalene?
Why is 1,2,3,4,5,8-hexahydronaphthalene (1) more stable than 1,4,4a,5,8,8a-hexahydronaphthalene (2)?

A follow-up question is about stability being estimated by counting the α-hydrogens.
In the first case, do we consider α-hydrogens individually for each double bond, or are common hydrogens only taken once?  If it is the former, then the answer would be 12, or else 8. Which one is correct?
If it is the latter, both have an equal number of hyperconjugating structures, i.e. H = 8. Therefore the stability of both must be equal. Is this wrong?

Symmetry? (Pretty weak argument though..)

It is not your fault, but these questions are really, really big garbage. There are zeroth order approximations, which are taught as some kind of holy grail of organic chemistry, like counting hyperconjugation contributors. This is not much more than a guess though and works accidentally some times. Also, stability is not an absolute concept; without a proper definition of the baseline, you can possibly generate any number of rankings. In this case, it is probably a good idea to ask: Which of these compounds has the higher hydration enthalpy; but you'd not use hyperconjugation for an estimate.

I think that the question should be more specified. (specific values indicating stabilities of two compounds, phase etc.)

@Patche this question came in my test.And high school organic chemistry that discuss much about mathematical values .

@Patche dear sir can you please confirm that 1st compound has $8$ hyper-conjugating H or $12$. I mean $12$ if we consider $2$ H individually wrt. to each double bond Carbon.

There is a cis/trans issue with the second structure. You might explore the heats of hydrogenation/combustion of hexenes that bear the substitution of the double bond. Welcome to ChemSE!

@Safdar I'm really sorry. but can you please tell me that  1,2,3,4,5,8 hexahydronaphthalene has 8 or 12 hyperconjugating H

@Newton Please don't use the comments section for extended discussion. I understand that you want to have an answer, but being patient is key here. This is not a discussion forum with a back-and-forth conversation style. Please take the [tour] to learn more about how this site works. As I previously said, the entire question is garbage and I am very sorry that you - a student - have to endure these terrible guessing methods. That being said, I will not endorse any count of any hyperconjugation contributors, it simply is not a reliable approximation and oversimplifies the chemistry behind it.

@user55119 Dear sir, can you give me any link or source where i can know more about.Simple Google search didn't gave me any satisfactory result.

Try this for a starter. http://ursula.chem.yale.edu/~chem220/chem220js/STUDYAIDS/thermo/Heat.pdf. With some  effort on your part, I'd prepare an answer for you.

Number of hyperconjugating structures for a pi-bond is the same as total number of alpha-hydrogen that are associated to it.
We consider alpha-hydrogen individually for each double bond to calculate number of hyperconjugating structures.

In the first compound, there would be 12 hyperconjugating structures.
This is because alpha-hydrogen which are common to both pi-bonds hyperconjugate with both of them, contributing in two hyperconjugating structures.So total number of hyperconjugating structures will be 12.
However, if you only need to count number of alpha-H, then the answer would be given by considering the common hydrogens only once. So number of alpha-H is 8, where the 4 alpha-H at C1 and C2 contribute in 2 hyperconjugating structures each.

However, the second compound has both its pi-bonds at its ends, each having 4 hyerconjugating alpha-hydrogen interactions associated to them. So total number of hyperconjugating structures in this case are 8.
Hence, (1,2,3,4,5,8-hexahydronaphthalene) is more stable than (1,4,4a,5,8,8a-hexahydronaphthalene).

i do believe your answer but why no one pointed me this point till now, If this was so simple. Infact i was literally begging to users to know whether this structure has 8 or 12 alpha H .Are you sure? Don't get me wrong i just don't want to input any wrong info.

@Newton Read Martin's comment.. It is a gross oversimplification

@Safdar i can understand. But in exams we can't leave one of the easiest question just stating fact"gross oversimplification" .  So i just want to know total alpha H in 1st compound for exam purpose. I'm in high school btw.

This is just neglecting so much, much chemistry.

@Martin-マーチン Hyperconjugation leads to stabiity of compounds having pi-bonds. Whenever sp3 hydrogen is next to a pi-bond, the sigma orbital of CH bond overlaps with vacant pi*(antibonding)-orbital of pi-bond. This results in delocalisation of the the sigma electrons that increases the entropy, and in turn, the stability of the compound. Also on overlap with the pi* orbital, the electrons occupy a lower energy level than they were at initially. Hence, Hyperconjugation is a valid concept to determine stability of such compounds

@SoumyadwipChanda This is a handwavy explanation at best. Yes, hyperconjugation is a stabilising effect, but it has a wide range from weak to strong. Simply counting possible contributors is just a little bit better than guessing. With these particular structures there are much more factors at play. Also, stability should be seen as a relative concept and with this exercise the baseline is not defined. Your answer also is solely based in a very crude model, it does not even attempt to check whether the model produces the correct result.

@Martin-マーチン I agree to this. Of course you cannot use hyperconjugation to compare some completely different compounds. But comparing stability of compounds having similar structures, more precisely isomers, Hyperconjugation can give reliable results. However, we can never be sure of such predictions unless we have the accurate data of heat of combustion or hydrogenation or something else. The two compounds being isomers, I can surely say that hyperconjugation will have a significant effect over their stabilities.

Disclaimer:
This post might be hard to read for some people. Some may even consider this a rant. You have been warned.
This answer will question the validity of the used models, as well as the basis for such exercises. (It will also point to a fundamental flaw of this specific exercise.) If you are a student, you might learn concepts that will later turn out to be inaccurate or outdated. This answer should give you some general context, but it will probably not be able to help you in an exam.

Introduction
I have previously stated in the comments how much I hate these exercises, I even called them really, really big garbage. There are several reasons for that. I am going to try to convince you step by step why I dislike these exercises, this one in particular.
Stability is not a very meaningful concept
There is a reason why there is no easy definition for stability. It is too fuzzy a concept with too many different connotations that basically everybody could understand something different. This is an ultimate flaw, and for these exercises, some kind of understanding of 'stability' is implied, but probably never properly defined.
Let's start with something tangible, one possible (and accepted) definition of stable; one that is so trivial you might have not even thought about it. Stable means something exists. In more official terms, i.e. in the gold book, it is called structural stability (10.1351/goldbook.ST07109):

Within the Born–Oppenheimer (adiabatic) approximation, this is associated with an energy minimum on a potential energy surface. Structural stability implies that any change in the coordinates of the nuclei can only increase the total energy.

I'm not absolutely happy with the above definition, as it can be read that only global minima are stable. If you start from a local minima, some changes in the coordinates will lead to a decrease in total energy; that is how different conformations work and eventually also reactions. So the changes implied by this definition should be reasonably small.
Obviously, this definition does not at all help us with the exercise. Both compounds are stable according to this definition, but we cannot say which one is 'more stable'.
From this we could go ahead and rank molecules according to their total energy. As long as we would be looking at isomers, this could actually work, but another question is how meaningful this approach is. I won't and cannot go into any detail or discussion how to obtain the total energy; for the purpose of this post just assume every molecule does have an exact total energy.
In the end the total energy is a number associated with a molecule. It will not tell you anything about the chemistry that molecule does. Almost all tangible and practical information is not contained in this number. Sure it offers an exact and consistent way of sorting things, but –in my opinion– an utterly useless one.
It is also problematic in a semantic way: you are using one term to describe a phenomenon which already has a name.
This definition also will not help in answering the question, because estimating this value is hard. Quantum Chemistry has plenty of options to estimate or calculate the expectation value of these compounds. Some are simple, based on empirical data, e.g. semi-empirical methods, some are a bit more complex, e.g. Hartree-Fock, Density Functional Approximations, some are very complex, e.g. Configuration Interaction, Coupled Cluster. Almost all of them you cannot do on a piece of paper in a reasonable timeframe.
That leads us to the point where we need another definition. The gold book actually has another definition for us (10.1351/goldbook.S05900):

As applied to chemical species, the term expresses a thermodynamic property, which is quantitatively measured by relative molar standard Gibbs energies. A chemical species $\ce{A}$ is more stable than its isomer $\ce{B}$ if $\Delta_\mathrm{r}G^\circ > 0$ for the (real or hypothetical) reaction $$\ce{A -> B}$$ under standard conditions. If for the two reactions:
\begin{align}
\ce{P &-> X + Y} & (\Delta_\mathrm{r}G^\circ_1)\\
\ce{Q &-> X + Z} & (\Delta_\mathrm{r}G^\circ_2)
\end{align}
$\Delta_\mathrm{r}G^\circ_1 > \Delta_\mathrm{r}G^\circ_2$, $\ce{P}$ is more stable relative to the product $\ce{Y}$ than is $\ce{Q}$ relative to $\ce{Z}$. Both in qualitative and quantitative usage the term stable is therefore always used in reference to some explicitly stated or implicitly assumed standard. The term should not be used as a synonym for unreactive or 'less reactive' since this confuses thermodynamics and kinetics. A relatively more stable chemical species may be more reactive than some reference species towards a given reaction partner.

This brings us back to the original dilemma, the implied understanding of stability. While we certainly can estimate the hypothetical relative molar standard Gibbs energy of the reaction, it actually won't tell us much about the chemistry. At least this definition will give us some handling on the exercise, i.e. the problem becomes finding 'numbers'.
Sometimes, but this is very wrong, stability is used as masquerading a different concept altogether, a kinetic concept. Stability may then wrongly be defined as the lower likelihood to react, in other words a lower reactivity means more stability. Now this brings back the already discussed semantic problem, but this time it is actually worse. There is also no reason to not use the proper terminology. The gold book defines reactive (reactivity) as follows (10.1351/goldbook.R05180):

As applied to a chemical species, the term expresses a kinetic property. A species is said to be more reactive or to have a higher reactivity in some given context than some other (reference) species if it has a larger rate constant for a specified elementary reaction. The term has meaning only by reference to some explicitly stated or implicitly assumed set of conditions. It is not to be used for reactions or reaction patterns of compounds in general. The term is also more loosely used as a phenomenological description not restricted to elementary reactions. When applied in this sense the property under consideration may reflect not only rate, but also equilibrium, constants.

So this is pretty much linked to the activation barrier. This is surely nothing that is asked about by the exercise, especially since no reaction conditions are mentioned. However, it felt necessary to be included here, since quite a few people will actually mix up the terms or even use them synonymously.
You might come across terms like air-stable which means you can handle a substance in a normal atmosphere without having to worry that it would decompose or react. This is exactly the problem that I mentioned before.
Another point worth mentioning is that some people use 'stable' to indicate whether a species is long-lived; this is also a wrong usage according to the above definitions. It becomes especially problematic when it is used synonymously with unreactive or even inert; but these are discussions for a later time.
In conclusion: There are two correct ways to define stable/stability. (1) Stable either means something exists as a local minimum on the potential energy surface. (2) As a relative concept, A is more stable than B if it costs energy to transform A into B.
Hyperconjugation and the problem of counting interactions
The gold book again gives us a definition for hyperconjugation (10.1351/goldbook.H02924), but I will only quote a portion:

In the formalism that separates bonds into σ and π types, hyperconjugation is the interaction of σ-bonds (e.g. C–H, C–C, etc.) with a π network. This interaction is customarily illustrated by contributing structures, [...] sometimes said to be an example of 'heterovalent' or 'sacrificial hyperconjugation', so named because the contributing structures contains one two-electron bond less than the normal Lewis formula [...].

The important takeaway from this is, that this is only valid within a formalism that separates into σ and π bonds. This concept does not (in this form) exist in Molecular Orbital Theory.
As previously mentioned, there are various ways to describe electronic structure. Many of them require more than the back of an envelope. Those descriptions are basically modeling the electron density at given nuclear positions; these are just mathematical tools to reproduce observables.
As such, hyperconjugation interactions are also just mathematical models and you cannot measure their stabilising factor. All numbers you might find online or in textbooks, are pretty much partitioning schemes of experimental data.
As a very simple example: You can measure the hydrogenation enthalpy of ethene and propene. You can then assume that the π-bond will (in first approximation) behave equally. The resulting energy difference can then be interpreted as the stabilising effect of hyperconjugation. You can do that for thousands of molecules and find some average energy value for these interactions.
That certainly is a valid scientific approach; the problem comes then if you neglect all the conditions that lead to this value and take it as a given constant.
It should be painfully obvious, that different σ-bonds will interact differently with other bonds. There is no reasonable justification to assume that a hyperconjugation interaction will always have the same stabilising effect. It should therefore come as no surprise that a carbon-hydrogen σ-bond located between two carbon-carbon π-bonds will have a totally different stabilising effect than a terminal carbon-hydrogen σ-bond.
Unfortunately, this is taught as some kind of holy grail of organic chemistry. Counting hyperconjugation contributors is at best a zeroth order approximation, an educated guess, a ballpark figure. Surely, you can use it to do a rough estimation, but you should always be aware about how imprecise this is.
It is also important that for a complete description of the electronic structure, you always need all resonance contributors, n.b. hyperconjugation is a more specialised form of resonance. Since these are hypothetical structures, they cannot be assigned an energy and they cannot be weighted that way. It really does need more involved methods to accurately describe this.
Focusing on this criterion alone also only ensures that you are neglecting any and all other possible influences. Dispersion will certainly have a different effect in one molecule than it will have in the other. There will be other mesomeric, or inductive effects; the conformational space will also be of concern.
So while $\pi \approx 3$ is a good guess to roughly estimate the size of a round window, you probably shouldn't use it to built your house.
The problem is the question
Now that we have gotten all of the general problems out of the way, there was one problem pointed out previously in the comments by user55119:

There is a cis/trans issue with the second structure. You might explore the heats of hydrogenation/combustion of hexenes that bear the substitution of the double bond. Welcome to ChemSE!

As if we hadn't already enough problems, the question is already ambiguous by specifying the molecules. In my personal opinion, this shows that the instructor did not spend enough time actually posing the exercise, really thinking about it. It shows that this exercise is targeted exactly at this specific counting exercise. To be honest, I would not have been surprised if the approximation had yielded a completely different result.
To be on the safe side, I performed a couple of calculations. First I ran a conformational analysis with CREST on the xtb level of theory, then I optimised the lowest structures with RI-BP86/def2-SVP in Orca. These are the relative electronic energies. (I did not bother with thermal corrections, since they are not accurate enough for this level, and qualitatively will probably not change the general order.
(1)          1-2-3-4-5-8-hexahydronaphtalene      0.0 kJ/mol
(2)    cis-1-4-4a-5-8-8a-hexahydronaphtalene     48.8 kJ/mol
(3)  trans-1-4-4a-5-8-8a-hexahydronaphtalene     26.8 kJ/mol

You can see from these numbers, especially between 2 and 3 where the number of hyperconjugation interactions is the same, that there are quite large differences. So using hydrogenation or combustion values is probably a better approach to this kind of question.
Additionally, those numbers don't tell you much about the molecules themselves or the chemistry they most likely will perform. In general I'd expect 1,4-cyclohexadiene derivatives to readily undergo oxidation to an aromatic species, but that is besides the point.
My personal opinion is that these counting models oversimplify chemistry beyond the point of usefulness. They do not further any understanding of molecular and electronic structure. It turns useful and educational models into formulaic use cases, which are applied without further understanding.

@ Martin has addressed the shortcomings of assessing “stability” by counting hyperconjugating C-H bonds. If by “more stable” one means which one of the two isomers, 1,2,3,4,5,8-hexahydronaphthalene 1 or cis-1,4,4a,5,8,8a-hexahydronaphthalene 2,  has the lower heat of combustion, formation or hydrogenation, then a decision can be made. Unfortunately, there does not appear to be any thermochemical data [NIST] on these compounds to answer this question.
If one assumes, not necessarily justifiably, that each double bond in these isomers is not affected by the presence of the other double bond, then one can model a solution based on known values for the heats of hydrogenation (ΔHho) of 1,2-cis-dialkyl and tetraalkyl-substituted double bonds. The more alkyl substituted a double bond, the less heat is produced upon hydrogenation, a trend that is readily verified with data from the NIST site. The heats of formation and hydrogenation of compounds are from the same source.
The ΔHho for an unstrained 1,2-cis-double bond is -28.3 kcal/mol as is seen in the hydrogenation of cis-2-butene to n-butane and cyclohexene to cyclohexane.  The heat of hydrogenation of  2,3-dimethylbut-2-ene (tetramethylethylene) to 2,3-dimethylbutane is -25.7 kcal/mol. Using these two values, the heat of formation (ΔHfo) of 1 and 2 can be calculated given the ΔHfo of  cis-decalin 3. Accordingly, diene 1 (ΔHfo = +13.5 kcal/mol) is more “stable” than diene 2 (ΔHfo = +16.5 kcal/mol)(blue numbers) by ~3 kcal/mol.

Notice that the monohydrogenation of cyclohexa-1,4-diene liberates only -25.2 kcal/mol upon formation of cyclohexene. This implies that the two double bonds, although non-conjugated, are not isolated in their reactivity. If they were isolated and equivalent in reactivity, the ΔHfo of cyclohexa-1,4-diene would be +27.1 kcal/mol. [Parenthetically, the conjugated cyclohexa-1,3-diene has a ΔHfo 1 kcal/mol greater than cyclohexa-1,4-diene.] Diene 1 has a similar arrangement of double bonds, albeit one of them is tetrasubstituted. Assuming that the -3.1 kcal/mol correction may be applied in the case of diene 1, the ΔHho would be lowered to -50.9 kcal/mol (red numbers). Whatever the true correction may actually be, the heat of formation of diene 1 will be lower than that for diene 2.


text:
How to oxidise iron in spinach to iron(III)
I'm planning an experiment to test the iron content of spinach. I plan to ash spinach, grind it, then dilute it in a solution which would hopefully oxidise the iron ions in it to $\ce{Fe^3+}.$ This is in order to get a reaction with ammonium thiocyanate solution in the end, which will allow me to determine concentration by colorimetry.
What should I dilute my ashed spinach into to oxidise the iron in it? Preferably something safe with the thiocyanate.

Use ceric ammonium sulfate.[1,2]  Quoting from reference 2:

2 Reagents
(i) 0.25 per cent ceric ammonium sulphate in 8.8 N sulphuric acid.
(ii) 40 per cent potassium thiocyanate solution.
(iii) (a) Stock standard ferrous iron solution - 100 μg iron per ml.
(b) Working standard ferrous iron solution - 0.3 to 10 μg iron per ml
2.2 Procedure
To five ml of clear water sample in a test tube 0.5 ml of ceric ammonium sulphate solution is added and mixed thoroughly by shaking. Finally, 0.5 ml of potassium thiocyanate solution is added and again mixed properly. Exactly 5 minutes after addition of thiocyanate solution, the absorbance of ferric thiocyanate complex is measured at 480 nm in a spectrophotometer (Spekol, Carl-Zeiss, Jena).
A series of freshly prepared working standard ferrous iron solutions (upto 10 ppm iron) were treated similarly and the absorbances measured at 480 nm. From the calibration curve, plotted with concentrations of different standard iron solutions against absorbances, the iron content of the unknown sample is evaluated.

References

Willard, H. H.; Young, P. Ceric Sulfate as a Volumetric Oxidizing Agent. Ii. Determination of Iron. J. Am. Chem. Soc. 1928, 50 (5), 1334–1338. DOI: 10.1021/ja01392a013.

Goswami, D. C.; Kalita, H. Rapid Determination of Iron in Water by Modified Thiocyanate Method. DSJ 1988, 38 (2), 177–182. DOI: 10.14429/dsj.38.4835.
Also available via CiteSeerx. (The pdf icon has a cached version of the article.)

@OscarLanzi Thanks for the answer, unfortunately doesn't look like I have access to ceric ammonium sulfate.

That is too bad, this is a pretty standard choice.  To get a better answer I think you will need to provide more input.  I assume you have some chemical knowledge and thus can identify some oxidizing agents to which you do have access.  We can then pick the best one.

https://www.sigmaaldrich.com/catalog/substance/ammoniumceriumivsulfatedihydrate632551037847911?lang=en&region=US

@OscarLanzi I am thinking maybe sulphuric acid would be a good choice. However it would need to be quite concentrated to work from my understanding. Do you think 1 molar sulphuric acid would be sufficient? Obviously I would later dilute it with de-ionised water since thiocyanate and concentrated acids don't go well.

One molar sulfuric acid is far from sufficient.  It would be completely dissociated into aqueous hydrogen and bisulfate ions, and neither of the latter will do the job you want.  Usually when chemists want sulfuric acid as an oxidant, they don't mess around.  They go for the fully concentrated stuff.

I see. My problem is that concentrated acids and ammonium thiocyanate do not go well together.


text:
Is this poor laboratory safety?
I'm a formulation chemist. My co-worker, is also a formulation scientist but has no previous formal training in chemical safety or lab chemistry settings.
I always work in the hood unless I’m just mixing fruit extracts or something non-volatile. My coworker doesn't ever work in the hood as they believe that since this goes in food it must be safe.
The lab is small and our work stations are pretty close. My coworker opens up reagent bottles and performs all other tasks on the bench top.
I don't think their reasoning is correct since in food items, the chemicals we work with are present in the ppm to ppb ranges whereas when a pure bottle of them is opened on a lab bench, they are in high concentrations. In addition we face prolonged exposure  ($8$ hr work days,$5$ days a week). The two scenarios are very different.
Also, I feel like I’ve had a sore throat ever since I’ve started working there.
I just don’t think these are prudent lab practices. Am I overreacting or does my coworker need to start working in the hood?

The lab should be shut down if there is no exhaust and your colleague and the higher up management do need to go through proper training.

Your coworker, like every chemist. absolutely must learn and remember the classic words of Paracelsus: “All things are poisons, for there is nothing without poisonous qualities. It is only the dose which makes a thing poison.”

"My coworker doesn't ever work in the hood as she believes that since this goes in food it must be safe." By that logic she would also have no problem with ingesting pure sodium and inhaling pure chlorine. After all, they are the ingredients for table salt, so they must be safe. Are you sure she has a chemistry education?

@Philipp she doesn’t. Studied nutrition in college

Or acetic acid aka vinegar. Can't you use that as an example for her?

@telcoM: I thought "dose makes the poison" comes from Galen (then again, Paraclesus could be quoting Galen)

Material Safety Data Sheets are available for all chemicals. It is sufficient to read those to see that most substances, indeed even those that are contained in food products, are quite harmful at high concentrations. Besides, I don't get it. It's not like the company would have to spend money to make you work safely: you already do have fume hoods, so why not use them?

This is more a comment than an answer, but too long for the former....
There are two things for you (and your company) to consider:

The SDS of the chemicals being handled - that will give you guidance for how best to handle a chemical. Flavouring chemicals like benzaldehyde, cinnamaldehyde, limonene all have irritation warnings, and need to be handled in well ventilated areas; others like diacetyl and allyl hexanoate are straight up nasty. And I don't mean to be patronising with this list of flavouring chemicals 101. I'm sure your list of chemicals is extensive, but they will all have SDS that will dictate how you should be handling them. Use that to base your arguments for change, not the opinions of an online discussion group.
Relevant building codes for laboratories that will specify the required number of air turnovers per hour. If your workplace is old, there is a good chance that ventilation is not quite what it should be. This is not an easy (cheap) problem to solve, but if the company is aware of any potential problems it will be easier to improve workplace practices of working in fumehoods.

Comments are not for extended discussion; this conversation has been moved to chat.


text:
Do we need to check for all kinds of symmetry in a compound to declare it achiral?
I know that a compound is achiral if it contains any one of the following kind of symmetry.
1.Plane of symmetry
2.Centre of symmetry
3.Normal axis of symmetry
4.Alternate axis of symmetry
It is difficult to write, for many compounds, its mirror image and then check using visualisation that if the image and compound are same or not, so we check for these 4 symmetries in molecule. My question is that for any compound do we need to check for all the symmetry elements one by one till we get a symmetry possessed by the molecule to declare it achiral, for example, does there exist any compound which has only alternate axis of symmetry and not any other kind of symmetry, so that any one will have to check all the symmetries one by one, till he reaches alternate axis of symmetry, to declare it achiral?
I know compound which have centre of symmetry, but not plane of symmetry, but  I don't know about a compound which has only alternate axis of symmetry and not any other kind of symmetry. Most of the achiral compounds that I have come across have plane of symmetry or centre of symmetry. So, do we need to check for all axis of symmetry or only centre and plane of symmetry, or any other shorter combination?

https://chemistry.stackexchange.com/questions/104409/use-of-axis-of-symmetry?noredirect=1&lq=1
You need to check for actual symmetry elements..

We need to check all 4 symmetries to determine whether a compound is optically active or not.
Consider the following compound. It has only Alternating Axis of Symmetry

Note that the rings are in perpendicular planes. The following diagrams illustrate the top view of the molecule.The stereochemistry of the methyl groups can be:

$S_4$ axis of symmetry is seen only in the following diastereomer where the methyl groups are anti to each other in each ring and the view looks like a Nazi cross from the top.

Umm.. So? do we need to check or not.. you might have left that out.. also references please regarding the chirality of since it may may depend on the diastereomer taken..

Your compound has undefined chiral centers; in which direction are the methyl pointing?

I have edited the answer listing all possible cases where only one of the diastereomers has the S4 axis of symmetry

But that compound also has two fold axis of symmetry.

Each ring coincides with itself when compound is rotated 180 degree about vertical axis.

Yes, that is a $C_2$ axis. But C axes are not taken under consideration while determining optical activity/chirality

@SoumyadwipChanda A better choice of term would be 'swastik' rather than you know what :)

卐 Yeah... But the world knows it better as Nazi-Cross


text:
Comparing stability of 2-propenyl cation and 1-propyl cation

Compare the stability of 2-propenyl cation and 1-propyl cation:
$$\underset{\text{2-propenyl cation}}{\ce{CH2=CH-CH2+}}\qquad \underset{\text{1-propyl cation}}{\ce{CH3-CH2-CH2+}}$$

In 2-propenyl cation we get resonance. So, 2-propenyl cation seems to be more stable, but due to the double bond (or, more precisely, the $\mathrm{sp}^2$ carbon) in 2-propenyl cation, an electronegative carbon atom which makes cation less stable.
In case of 1-propyl cation due to inductive effect cation is getting stabilized, but we know resonance is more stabilising than inductive effect.
I would answer that 1-propyl cation is more stable than 2-propenyl cation because we get $\mathrm{sp}^2$ or a more electronegative C in 2-propenyl cation making it less stable.
I'm really confused which factor is more effective: stability of resonance or destabilisation due to the $\mathrm{sp}^2$-hybridized carbon in 2-propenyl cation.
What would be a valid zero-order approximation for this?

Stability order -  $2$-propenyl cation>$1$-Propyl cation
Resonance has way more effect on the cation than that tiny-whiny little weak $\mathrm {sp}^2$ hybridised carbon

Electronic configurations are to be written upright, See here for a list of what should be upright and what shouldn't..

@OscarLanzi Dear Sir, i'm at very initial stage of learning organic Chem. We haven't covered whole IUPAC in our school but i saw a similar question on chegg(link provided below) according to them it's name is 2-propenyl cation. If i'm wrong please correct me it will help me alot in future. Thanks,

@OscarLanzi link of question -   https://www.chegg.com/homework-help/2-propenyl-cation-appears-primary-carbocation-yet-considerab-chapter-6-problem-49p-solution-9781133952848-exc


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Deriving an expression for reaction time in terms of the total concentration

Consider the dimerization of protein $\ce{A}:$
$$\ce{2A <=> A2}$$
with forward rate constant $k_1$ and backwards rate constant $k_{-1}.$ Derive the following expression for the reaction time in terms of the total concentration of protein
$$\frac{1}{\tau^2} = k^2_\mathrm b + 8k_\mathrm ak_\mathrm b[\ce{A}]_t,$$
where $[\ce{A}]_t = [\ce{A}] + 2[\ce{A2}].$

I assumed the 1st order in the forward direction and the 2nd order in the reverse direction. Rate law:
$$-\frac{\mathrm d[\ce{A}]}{\mathrm dt} = k_1[\ce{A}]^2 - k_{-1}[\ce{A2}].\tag{1}$$
At equilibrium
$$k_1[\ce{A}]^2_\mathrm{eq} - k_{-1}[\ce{A2}]_\mathrm{eq} = 0.\tag{2}$$
I then substituted that into the rate law and factored out the rate constants with the aim of getting rid of all of the equilibrium concentrations. The equation indicates that
$$\frac{-1}{2}\frac{-\mathrm d[\ce{A}]}{\mathrm dt} = \frac{-\mathrm d[\ce{A_2}]}{\mathrm dt} \quad\implies\quad \frac{\mathrm d[\ce{A}]}{\mathrm dt} = -2\frac{\mathrm d[\ce{A2}]}{\mathrm dt}.\tag{3}$$
I then got stuck. I saw something where you define a displacement variable $x$ and then try to get the rate law in terms of $x,$ but I've tried that approach and keep running into dead ends.

For formatting, See here and here. For a more detailed MathJax guide, look here, minor other details

In my opinion, there is no "reaction time" for this equilibrium. An equilibrium needs an infinite amount of time to be attained.

Just for fun, you can compute the time integral of (1) and substitute $\tau$ for the end time.Than you will see the final relation of reaction quotient Q and K.

What are $k_a$ and $k_b$?

Let the amount of $A_2=x$ and write down $dA_2/dt=dx/dt=2k_1[A]^2-k_{-1}[A_2]$ and find x the amount reacted in terms of $[A_0]$ and $[A]$ and substitute into the equation. Separate variables, ie, integrate in $x$ and $t$ separately. The integral in $x$ is just horrid but look for the constant square root term in front of the log terms.   This is equivalent to $ 1 / \tau ^2$. If $[A_0]$ is the initial A I found $1/\tau^2=4k_1k_{-1}[A_0]+k_{-1}^2$ which is related to your answer. (btw. should your $[A]_t=2[A]+[A_2]$ )

No I'm pretty sure the total [A] is correct. My professor literally copied and pasted it out of  our physical chemistry textbook

@Maurice the relaxation is first order (or pseudo first) and as such has a well defined lifetime or characteristic rate constant. The general solution is of the form $\ln( f(k,c))=-w(k)t$ where $f(k,c)$ is some (usually complicated) function of rate constants and concentrations and  $w(k)$ a function of rate constants and initial concentrations so has a constant value so that $1/\tau\equiv w(k)$.


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My Misconception of Entropy
It was recently brought to my attention that my understanding of entropy is wonky at best.
In my experience, entropy was introduced (superficially at best) during general chemistry/foundations of inorganic chem and described in terms of order/disorder of a system, usually followed by some messy room analogy. In one of my textbooks, the author, Gary Wulfsberg, was discussing how a reaction tends to favor the products "if it increases the dispersal of ions/molecules over a larger volume of space..."(Wulfsberg, G., 2018). Wulfsberg goes on to say that

The measure of this dispersal or disorder is known as the entropy (S) of the substance. A
positive entropy change for a reaction indicates increasing dispersal or disorder
(Wulfsberg, G., Foundations of Inorganic Chemistry; ch. 4, pg. 200)

which I interpreted it as him saying that all systems that increase in entropy have a corresponding increase in disorder.
Later in my undergraduate career, Boltzmann's entropy was introduced during thermodynamics and described by my professor as the amount of micro-states available for the particles within the system and that an increase in entropy corresponds to an increase in the states that the system can exist in.
All was fine and peachy until recently, when I came across an article that discusses the Shannon Measure of Information (SMI) and entropy. In an article by Arieh Ben-Naim, he talks about how the idea of order/disorder in relation to entropy is not necessarily correct, in fact it is a fallacy that does not hold true nor can order/disorder be measured definitely for all systems. He states,

It is true that many spontaneous processes may be viewed as proceeding from an ordered to a disordered state. However, there are two difficulties with this interpretation. First, the concept of order is not well-defined, and in many processes it is difficult, if not impossible, to decide which of the two states of the system is more or less ordered.
J. Chem. Educ. 2011, 88 (5), 594–596

Additionally, he talks about how some systems do have "order parameters", however, it is not in relation to entropy and that not every process where an increase in entropy is observed has a corresponding increase in disorder. He later goes on to describe the SMI treatment of entropy "as the number of binary questions one needs to ask to find the location of the particle." Hence, if the number of yes/no questions one needs to ask to find the location of particle increases, so has the thermodynamic entropy.
So here is my question
Is entropy described by Boltzmann/statistical mechanics the same as the entropy described by Shannon information theory?
Additionally, is there any validity in relating order/disorder in describing the change in entropy of chemical systems?

Thanks for raising this query. Hope we will see a lot of activity and various view points. The recent terminology in Atkins and others entropy as "dispersal of energy" is due to the efforts of Frank L. Lambert. Many textbooks adopted his terminology. When he was alive, he used to discuss this in a chemistry education forum. If I understood him correctly at that time, he meant to say that entropy is a measure in how many ways energy can be distributed hence the word dispersal of energy.

The biggest problem was created by Shannon himself by using the same word "Entropy" which really led to this "messy room" and "shuffled cards" stories.

@M.Farooq Absolutely, it bothered me that my understanding of such a fundamental concept was wrong. I could blame my teachers but it really is the individuals responsibility to question things and ensure the validity of ones claims. I appreciate your comments/information

Let's distinguish the "fundamental concept is wrong" from the "the often used, simplistic explanation for a fundamental concept is wrong/totally misleading". Two very different situations. Entropy has a very well done definition in statistical mechanics and thermodynamics, and these definitions hold well to chemistry, too. The problem is when people want to explain everything at a 5 years olds level: more often wrong than enlightening. The entropy as a disorder is a very unhelpful concept in chemical systems.

I think my comment was misinterpreted. That is meant as I was wrong, not the concept of entropy itself. That was a reflection of my own misunderstanding. Unfortunately I couldn’t edit the comment beyond five minutes after posting

This is by the way a huge discussion somehow ongoing. In my modest opinion is just the term disorder that is ill-defined. A big stadium with numbered places and supporters owning a ticket for a specific place can be see full of entropy but also very ordered. Yet the random selection of the place should increase both, if I am right. I am also on the line of @Greg.

Above it reads "should increase both entropy and disorder, if...."".

I'm with @Greg on this, originally it was described (by Boltzmann ?) as 'a measure of disorder' but the 'measure of' got lost on the way hence the confusion. Why not either think of it in the classical thermodynamic sense only as $\pm T\Delta S$  as related to heat or as the number of ways of placing particles into energy levels/boxes etc., which is basically Boltzmann's approach, when  an atomistic approach is needed.

@Alchimista There are several nice examples for entropic effects in chemistry, a chemical equilibrium. For example, a rotating methyl group in a solid crystal, which you can call disorder if you want. But entropic factors can come eg from high spin / orbital multiplicity of an electronic state or high symmetry of a structure. It is very counter-intuitive to label the high symmetry cases  as "disorder".

@dval98 This question has been flagged for needing more focus. wanted to let you know. IMO, this can be fixed as follows. Q2 and Q3, Q5 are opinion based and can be removed. However an answer to Q.5 can be asked as a different question using the tag [reference-request]. Merging Q.1 and Q.4 would make the question focused. However, this last idea may be wrong since I do not know enough to discern between the two. If they are not same, ask the two as two different question linking the two together. For Q.5: https://chemistry.stackexchange.com/questions/37303/resources-for-learning-chemistry

I also recommend reading this article: https://pubs.acs.org/doi/abs/10.1021/ed079p187

@Safdar I apologize for that. Please let me know if my edits will suffice.

This seems to be a very rampant bee in some highschool/undergrad teachers' bonnets. The explanation with order/disorder is qualitatively right and useful, and that's that. The Boltzman/thermodynamic/statistical interpretation is, beyond doubt, quantitatively correct.

@Greg I copy it and nothing in my comment is contrary to your last comment. But I can add more, the idea entropy - -> disorder seems also useful. It should be taken with a grain of salt. At the end we might say universe is going to be well ordered, in the sense that it is going to be empty and dark. Not to open a discussion on cosmology, but to put things to the extreme. What remains certain is that there will be no energy to extract.

I wonder why this question was closed. The OP has edited it to be more focused, and it seems a very legitimate question how a very common (and often taught) interpretation of a central thermodynamic concept holds up.

@Greg, the question was closed before the last revision, you can vote to reopen as the question is focused now..

The association of entropy with disorder is anthropocentric. "Disorder" is a concept derived from our experience of the world. The association with "disorder" is clearer once we explain what we mean by "order". The following definition among those provided by Merriam-Webster most closely fits the intended meaning:

a regular or harmonious arrangement

Since regularity always implies lower entropy, all else being equal, it is therefore fair to associate "order" with lower entropy.
The association with "order" or regularity also syncs with the concept of entropy according to Boltzmann's statistical mechanical definition ($S= k_\mathrm B \log \Omega$). $\Omega$, the number of microstates available to the system, can be quantified using the entropy. More possible unique microstates implies a higher entropy. Greater regularity implies more constraints regarding arrangement of the system and therefore less possible microstates. Solids are usually more regular and therefore have lower entropy than fluid states at the same T. Same when comparing gases and liquids. The possible microstates increases from solid to liquid to gas.
This also jives with the informational-content definition. You can use less information (use a more compact description) to describe an orderly (regular) system. You need more information to describe all possible arrangements of molecules in a gas or liquid than in a solid. Think of entropy as measuring the length of the recipe required to build all possible arrangements of the system.

How would we define regularity at molecular level? Is it periodicity? How would explain regularity in liquids vs. gases?

@M.Farooq For a gas you need to describe more possible arrangements, each unique, than in a liquid, to describe the system. Similarly on going from solid to liquid (where the difference is more striking). For a simple description of a solid all possible arrangements can be considered permutations of one template. Once you describe that one template and the way of permuting positions you are done. For liquids you are somewhere inbetween. You see this e.g. in g(r).

The topic deserves going through the examples in more detail, including those in the comments to the OP. I find the idea of dispersal of energy appealing at times but not entirely satisfying. For instance, in an isolated system (say a gas in an adiabatic box) what exactly do you mean by energy "dispersal"? Are you talking about the kinetic theory of gases? The Boltzmann distribution?

Yes, I am not fully satisfied with the wordings of "energy dispersal." Frank Lambert, who was behind this terminology indeed did a big service by getting rid of order-disorders mythology from many textbooks. On the contrary, he also introduced "energy dispersal" concept. Which is a bigger evil entropy or energy dispersal? Only time will tell.

Trying to read the original work of Clausius will require a year to understand where he was coming from and what was going on in his mind when he came up with this idea. His book is available in English.

@M.Farooq It seems you are channeling Kuhn and other philosophers. Granted it is a chore to read something written in those days. Clausius was apparently mathematically minded and attempted to derive thermodynamic principles on a sound mathematical basis. Therefore dense and tough going for non-mathematicians. It would take some time to become comfortable with his style but maybe not a whole year :-)


text:
Is plane of symmetry a necessary and sufficient condition for optical inactivity in coordination compounds?
In organic chemistry, we have to check for all three types of symmetry in a compound to check its chirality, ie, plane, alternate axis and centre of symmetry. But in coordination compounds, do we need to check all the symmetries to check its chirality? The ligands are supposed to be achiral. The difference between the two being that in coordination compounds only one "chiral" center is present but in organic compounds it can be more than one.
All the achiral coordination compounds of any coordination number which I have come across have a plane of symmetry. But for those which don't have, I have to check whether it's image coincides with itself or not. So, is plane of symmetry a necessary and sufficient condition for achirality of coordination compounds?
This thing is necessary for my purpose, as I have to solve problems in limited time, so I cannot use the orignal method always.

Related: https://chemistry.stackexchange.com/questions/123121/link-between-centrosymmetry-dipole-moment-and-chirality

I remember my coordination chemistry professor at uni drawing a tetracoordinating chelate ligand with a central metal on the blackboard. The tetrahedral complex had improper rotation (which we spent two minutes proving by him drawing the mirror image). It was thus achiral. Alas, it’s not mentioned on his webpages …

Does this answer your question? What is the perfect definition for chirality?

The number $\pi$ for bowhead whales† is still 3.1415... Same thing here.
Chirality of coordination compounds is the same thing as chirality of organic compounds. If all your symmetry elements are just rotations, you have it; if some are improper rotations, then you don't. It is as simple as that, and is not going to be any simpler.
Can you just check for the planes and call it a day? Well, you kinda can, and that will do, until you come across a compound which doesn't have a plane, but still is achiral because of some other symmetry element.
Are there such compounds? Well, that's like asking whether there is a place on Earth where three bricks stand on top of each other. You may google long and hard, or you may apply for a travel grant to visit countries with rich traditions of brickwork masonry... or you may just take three bricks and put them on top of each other. That's it; problem solved.
Here are my bricks. I claim that the tetrahedral $\ce{[Zn(NH3)4}]^{2+}$ has an inversion axis $\bar4$ and hence is achiral. You may point out that it has a plane as well. Fine. Let's give it some substituents: change each ligand to $\ce{N(CH3)3}$. What? Does it still have a plane, given that everything which rotates is rotated to the appropriate position? Fine. Let's give it different substituents. Change each ligand to $\ce{CH3NHC2H5}$. Where is the plane now?
So it goes.

† There was an old anecdote about an even more old paper on biophysics which was said to include some volume calculations and some crude approximations of a whale as a cylinder, then of course the number $\pi$ showed up, followed by the hilarious phrase along the lines of "The number $\pi$ for bowhead whales is about 3.14".

But the chirality introduced due to ethyl methyl amine is because of the chirality of the ligands and not because of the arrangement of different ligands around the central atom. I have assumed the ligands as non chiral.

@siddharthkalra   If the ligands are chemically different, because you arrange around a central ion $\ce{M^{4+}}$ at once $\ce{F-}$ and $\ce{Cl-}$ and $\ce{Br-}$ and $\ce{I-}$, than the complex is chiral even if the ligands are not.  Well if the four are chemically different like methyl, ethyl, propyl, ... (which includes the «if at least one them is chiral»), the complex is chiral, too.

No. A plane of symmetry is a sufficient, but not necessary criterion to exclude optical activity of a molecular compound.  Equally sufficient, but not necessary criterion for the absence of chirality is the presence of a centre of inversion.  Note that you probe for these criteria independent from each other the whole molecule.
An easier example of organic molecules suitable for the first criterion is (2R,3S)-tartaric acid - equally known as meso-compound - where you may draw a mirror plane across the molecule even if you have two examples of atom centred chirality in the molecule present.  (It is not good to call the stereogenic atoms «chiral atoms».  Beside atom centred chirality, there equally are helical and axial chirality, too.)
By training, you are going to identify these compounds by inspection of their formulae:

(credit)
Don't hesitate to build models of the molecule in question and to redraw the structure formulae like the following to get more familiar with the topic:

(credit)

 Only the two first columns of the four depict a mesocompound.

But I was talking about coordination compounds having only one central metal atom and having non chiral ligands. I am fine with chirality in organic compounds. I just wanted to ask if there is any shorter method to check chirality in such  coordination compounds by just checking plane of symmetry, as all the coordination compounds I have come across have a plane of symmetry if they are achiral.

@siddharthkalra No.  As stated, you probe the molecule / complex for a mirror plane which either is positive (is present), or negative (is absent).  And you probe the molecule for the presence / absence of a centre of inversion.  The order of testing them may be formalized in a flowchart (like here) if aiming to determine the point group of the object (e.g., IR spectroscopy), but neither one of the two tests is a necessary and sufficient condition for the other to yield either answer.


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Melting point of objects and food
What is the melting point of egg yolk?
Well, generally, when we break an egg, the yolk is in liquid state. After we pour it on a pan, the egg starts to cook and it hardens. My question is, can an egg melt/boil ?
What are the conditions to be imposed?

Most foods never melt. Instead, they decompose.

@IvanNeretin that does mean that the egg does not has a definite melting point? since it'll split up?

That's right, it doesn't melt at all.

Defined melting point requires pure substance or in some cases well defined mixture of few components, which do not decompose at melting temperature. Egg yolk is not such a case.

Egg yolk is a complex mixture including a lot of proteins. Heating proteins does not melt them, it causes them to denature or unfold. Once denatured, the proteins interact to form a gel-like solid. If you continue to heat up the solid, it will burn.

As Poutnik said, the melting point is well defined for pure substances. In the case of egg yolk, it is not a pure substance and also when you heat it, some molecules decompose. So we can't measure or even define a melting point for it. Also, the temperature is not constant, when the egg is melting.
A substances' phase doesn't get influenced only by temperature. Maybe it is strange that heating the egg yolk in a pan, makes it to behave like a solid. Actually, some complex changes in intermolecular forces are getting done.
If you want to cause an egg yolk to melt, I think that the only work to do is to heat it under the normal pressure.


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Is there any theory more advanced than MOT?
I am currently going through molecular orbital theory(MOT), I should appreciate it's a very nice theory and it's helping me to fill the gaps of normal hybridization concepts and valance bond theory(VBT). But I am unaware about it's limitations seemingly it's the most advanced theory and have the capability of explaining everything. Although we know everything has it's limitations so if exist then what are they?
It will be also interesting to know about some modern viewpoints, accepted or proposed theory, and concepts regarding this stuffs.

maybe not 'advanced' than MOT, but DFT and QTAIM are some other theories for molecular physical chemistry.

MOT is more of a collection of different methods that are using molecular orbital approach in one way or another. Most calculation methods like DFT are MO based, in principle.

MO theory is more of a descriptive guide than a rigorous mathematical construct. The main idea of molecular orbital theory is that the electrons in atoms can be described by linear combinations of atomic orbitals (LCAOs), which themselves are the exact solutions to the Schrodinger equation for single electron atomic systems.
This idea can be applied in a more mathematically quantitative way by use of the Hartree-Fock (HF) method. HF is essentially MO theory put into practice. HF takes as input the geometry of a system (i.e. the spatial coordinates of all atoms in your molecule) and a set of "basis functions" which are usually sets of 3D gaussian functions centered on the atomic nuclei of the system. These basis functions are your "atomic orbitals" in MO theory. The HF method takes linear combinations of the atomic orbitals to generate a set of molecular orbitals which are usually more delocalized. These are the molecular orbitals of MO theory, and we can calculate them using the HF method running on a computer.
There are several approximations involved in HF theory, which the descriptive MO theory inherits.

The Schrodinger equation (SE) itself is an approximation. The SE is not exact as it fails to account for so-called relativistic effects. These are effects originating from Einstein's theories of special and general relativity. Some examples of relativistic effects are spin-orbit coupling and relativistic contraction of orbitals, especially in heavy atoms. The straightforward HF method doesn't take relativistic effects into account. Starting instead from the Klien-Gordon or Dirac equations will recover (some of) the missing relativistic effects.

The HF method assumes a complete separation between the movement of electrons and nuclei, known as the Born-Oppemheimer approximation. Basically, electrons are assumed to equilibrate instantaneously to the positions of atomic nuclei. This usually isn't a problem because electrons are much lighter than atomic nuclei so they do move much faster. Not a bad approximation in most cases.

Electron correlation. Even if we ignore the previous two approximations, the HF answer (and therefore the MO theory prescription) misses out on a very chemically important effect known as electron correlation. Electron correlation arises because a single set of molecular orbitals combined into a Slater determinant (in order to satisfy the Pauli exclusion principle) is not enough to fully describe the true exact solution to the Schrodinger equation for a molecular system. One must take linear combinations of many Slater determinants to improve on the HF answer. Electron correlation is responsible for effects such as the Van der Waals dispersion force. Another way of thinking about Electron correlation is that it is the energy that arises due to the dynamic Coulomb repulsion between moving electrons (although this picture is incomplete).

In summary, an exact molecular theory would need to account for Einstein's theory of relativity, combine the movement of atomic nuclei with electrons, and account for the dynamic correlations between different electrons in a system, in addition to being a proper quantum mechanical theory.
There are some quantum chemistry theories out there that incorporate relativistic effects into them. For example, the Douglas-Kroll-Hess approach is similar to HF theory, but begins from the Dirac equation and so incorporates relativistic effects explicitly. I believe there are also approaches that don't use the Born-Oppemheimer approximation, though I'm unfamiliar with them.
There is a massive amount of research and development into the so-called post Hartree-Fock methods. All of them attempt to account for electron correlation in various different ways. The main issue with the post HF methods is that the results (energies and wavefunctions) are often incredibly computationally demanding to actually compute, except on very small molecules. The most exact of the post-HF methods is the Full Configuration Interaction (FCI). With a sufficiently large input basis set, FCI produces an exact answer to the Schrodinger equation under the Born Oppenheimer approximation. Other post-HF methods include: Møller-Plesset perturbation theory, Coupled Cluster theory, and Multi-Configurational Self Consistent Field theory. All of these post HF methods are more accurate than the MO theory picture, but they are also way more difficult to visualize and understand for new students.

There is, probably more importantly, DFT, which is in principle exact. There are various approaches for orbital-free implementations, too. MO itself is - a quite handy - approximation and only a mathematical approach to a/the wave function.