texts:
Consider the following species:

  $$
\underset{(\text{A})}{\ce{\overset{⊖}{O}H}}
\quad
\underset{(\text{B})}{\ce{CH3-\overset{⊖}{O}}}
\quad
\underset{(\text{C})}{\ce{\overset{⊖}{C}H3}}
\quad
\underset{(\text{D})}{\ce{\overset{⊖}{N}H2}}
\quad
$$

  Arrange these species in their decreasing order of nucleophilicity.

  (a) C > D > A > B
  (b) B > A > C > D
  (c) A > B > C > D
  (d) C > A > B > D

My teacher taught in polar protic solvent nucleophilicity is inversely proportional to basic character. I assumed solvent to be $\ce{H2O}$ as solvent was not mentioned in the question.
As acidity order is

$$\ce{H2O} > \ce{CH3OH} > \ce{NH3} > \ce{CH4},$$

so basicity order should be

$$\ce{CH3-} > \ce{NH2-} > \ce{CH3O-} > \ce{OH-},$$

therefore using above proportionality I arrived at the nucleophilicity order

$$\ce{OH-} > \ce{CH3O-} > \ce{NH2-} > \ce{CH3-},$$

but you can see the option is not even given. Why is it so?


texts: Does the order of protonation/deprotonation in the formation of hemiacetals matter?

texts:
In the mechanism depicted above, deprotonation occurs first and then protonation.
Can this order be changed? If not, why?


texts: Molar mass and molar volume of monochloroethylene

texts:
Monochloroethylene gas is used to make polyvinylchloride (PVC). It has a density of $\pu{2.56 g L-1}$ at $\pu{22.8 ^\circ C}$ and $\pu{101 kPa}$. What is the molar mass of monochloroethylene? What is the molar volume under these conditions?

$$PM=dRT$$

$$M=\frac{\pu{2.56 g L-1}\cdot\pu{295.8 K}\cdot\pu{0.0821 atm L mol-1 K-1}}{\pu{0.9968 atm}} = \pu{62.37 g mol-1}$$

After this I can't find molar volume. Which formula should I use?

I know $PV=nRT$, but without knowing the gas mass I can't use this formula, I believe.


texts:
I came across this structure of $\ce{HF2-}$ and realized that the bond shown between H and F is a hydrogen bond.

$$\Large\ce{[F-H-F]-}$$

HF hydrogen bond are the strongest hydrogen bonds we know, but still they are not real bonds.
Writing the molecular formula as $\ce{HF2-}$ will give anyone an idea that the bonds between H and F are only covalent bonds.

Why do we write the molecular formula of $\ce{HF2-}$ as this and can you throw more light on its structure?
Have I correctly understood the structure?


texts:
Work so far:
Molality = mol solute/kg solvent
Molarity = mol solute/L solution

So for molarity to exceed molality in the same solution, the numerical value of
kg of solvent > L of solution

From my experience this never happens. However by applying this to a very dense solvent, could the mass of solvent actually exceed the combined volume of solvent and solute. I am aware that volumes are not additive, and so if the density of a solvent is 10 g/mL the density 10 times of water and 0.5 M 2 L of HCl is added to 4 L of solvent, mass of solvent would be 40 kg solvent could the volume actually be greater then 40 L? Is there an example of a physical system where molality is lower then molarity?


texts:
I was trying to name the above compound which happens to be 3-(2-aminoethyl)-2-methylcyclohexan-1-ol.

On my first attempt, I had named it 3-(ethyl-2-amine)-2-methylcyclohexan-1-ol.

Which one is correct?


texts: How can I draw metallocenes in ChemDraw?

texts:
How can I properly draw the structure of metallocenes (e.g. ferrocene) and similar sandwich compounds in ChemDraw?

In particular, two problems cannot be solved with the usual workflow when building a molecule in ChemDraw:

How can I draw a bond starting from the centre of a ring structure (e.g. cylopentadienyl or benzene) if there is no atom?
How can I connect the centre of another ring structure to an existing molecule with the correct bond length and angle?

This question came up among the editorial staff of the chemistry section of the German Wikipedia. I have answered this question there myself, and I think it might be useful to share the solution to this problem here.


texts: Are all alkene geometrical isomers achiral?

texts:
I was reading a book and it tells that alkene geometrical isomers are achiral.
I wanted to know that is it applicable for alkene geometrical isomers?
Thanks in advance.


texts: Why rutile structure have primitive unit cell instead of body centered?

texts:
In the literature (Wikipedia), I read that $\ce{MgH2}$ have a structure of rutile. Then, I looked at its space group which is $P4_2/mnm$. From this notation, I understood that it possesses a (tetragonal) primitive unit cell. However, when I looked at the structure of $\ce{MgH2, Mg^2+}$ ions are seemed to be ordered in body centered. Indeed, at each corner there are $\ce{8 Mg^2+}$ ions and in the middle, there is another one. Then, why is this called $P4_2/mnm$ given that it resembles more to body centered? Is there any smaller unit cell hidden here?

Thank you in advance.


texts: rate determination by 1H NMR spectroscopy

texts:
Currently I investigate a reaction where a starting material A reacts with an excess of thiophenol B towards products C and D.  As shown by recurrent TLC analysis of the reaction, the formation of D is slower than the one of C, while A and B are still detectable.

Perhaps the reactions are consecutive, i.e.

$\ce{A + B ->[k_1] C ->[k_2] D}$

or they are simultaneous, i.e.

$\ce{D <-[k_2] A + B ->[k_1] C}$.

A, B, C, and D are distinguishable by 1H NMR spectroscopy; NMR data of the purified compounds A, B, C, and D were  recorded successfully.

Based on a recurrent 1H NMR spectroscopy, I would like to use the integrations of the signals to determine the rate constants; perhaps there is evidence for the first case (similar to Bodenstein principle).  The advancement of the thioetherifications alter the multiplicities of the signals observed, and simultaneously indicator signals vanish.

Question:  Prior to get work on my data, where may I find a tutorial of reactions with known starting material(s)/product(s), determined rate constant(s) and NMR data-used-to-determine-these-rate-constants?


texts: Determining mol/L at STP from volume and mol fractions in a CFD program

texts:
I'm using some CFD software and the outputs are a bit unusual so I thought I would double check my understanding on how to do these conversions.

The data available per cell is: cell volume, particle volume fraction, average fluid density, mol fraction of gas species, temperature, pressure

I am trying to come up with the mol/L at STP as a way of normalizing for density effects to compare concentration of a gas species throughout the height of a reactor. Temperature and pressure vary wildly, partially because this is a fluidized bed and solids distribution plays a big role in pressure.

So far my process has been convert from mol fraction to mass fraction.

And then multiply (cell volume-cell volume*particle volume fraction) by average fluid density to get gaseous mass in the cell. Then I can use the mass fraction to determine the amount of mass for a given species. Obviously at this point I have the mols of each species.

The problem is then I need the density of that specific species at a given temperature and pressure (currently working at temperatures around 950 C and 110kPa but they very cell by cell obviously) to get back to volume. Is the only way to do this to estimate the density?

The other problem is that let's say I do get the volume by estimating the density. Then I convert to volume at STP by multiplying by 273 K/T and P/101325 Pa or whatever it is. Are the mol fractions I had at non-STP still usable? Or do I just take these volumes and divide by 22.4 and that's the mols I should be using.

Can someone please straighten out my thinking on this. Also are there any good sources for density of a gas species as a function of pressure and temperature. Everything I look at online seems really bad.


texts: 6463-T6 aluminum oxidation and role of water and ethanol vapor

texts: Our issue...in a nutshell:    We use 6463-T6 aluminum as a sampling "cell" for analysis of water and ethanol vapor mixtures in both wet and dry gas variations. As I understand it, the aluminum oxide covering our cells surface is being or has been previously damaged and causing micro-abrasions of its surface. This allows water vapor to "attach" to the cells surface which negatively affects our testing process. Incomplete removal of the water or ethanol vapor within the cell is a failure. We have looked at methods of cleaning the cells to essentially create a newer cleaner oxidized surface. Acid baths, boiling in vinegar, etc.. now we are considering how the metal surfaces pH value can affect the quality or this aluminum oxidation. We are kind of stuck and any assistance on testing protocols or processes to achieve our goal would be appreciated.


texts: Why is H in OH group is more shielded than in H in CH2 group (ethanol NMR spectroscopy)?

texts:
I am confused with this $\mathrm{^1H}$-$\mathrm{NMR}$ spectroscopy result:

Shouldn't $\ce{H}$ in $\ce{OH}$ group the singlet be more towards the left of the $\mathrm{NMR}$ spectrum?
It is near the highly electronegative atom $\ce{O}$ rather than the two $\ce{H}$ in $\ce{CH2}$ group they have a weak eletronegative atom $\ce{C}$ so it shouldn't be that desheilded.


texts:
Why is the melting point of p-toluenesulfonic acid monohydrate higher than that of anhydrous p-toluenesulfonic acid?

Compare for example the melting point of benzenesulfonic acid hydrate, which is lower than for anhydrous benzenesulfonic acid.


texts:
So I was reading benzotriazole's synthesis is o-phenylenediamine with acetic acid and sodium nitrite.

Is this a reversible process?

Not even specifically to o-phenylenediamine but any derivative.

phenylenedaimne's (usually para) and derivatives and generally aromatic amines form various colour dyes on old colour photographic films that I like to experiment with as a hobby.


texts:
I know this question may sound to be not inherent with chemistry, but since making the sugar wax paste involves acids and heating, I thought this would be the right place.

Preparing the paste is quite simple:
1 cup of sugar, 2 tbs of lemon juice and 2 tbs of water. Then the process expects to heat the compound until it becomes abra colored. The the mixture is moved away to cool down.The result would be a malleable and sticky paste at ambient temperature. My problem is that my paste becomes really hard and impossible to shape.

What could I do to avoid the compound to become a brick?


texts:
I was balancing this reaction when I found an unusual compound had been formed.
$$\ce{Cu(s) + HNO3(aq)-> Cu^{3+}(aq) + NO(g)}$$

My attempt:

Balancing oxidation number:
$$\ce{Cu -> Cu^{3+} +3e^-}$$
$$\ce{3e^- + NO_3- -> NO}$$
Balancing hydrogen and oxygen atoms:
$$\ce{3e^- + 4H^+ + NO3- -> NO + 2H2O}$$
Adding $\ce{3NO3-}$ on both sides to form compounds:
$$\ce{3e^- + 4H+ + 4NO3- -> NO + 2H2O + 3NO3-}$$
Adding both half reactions
$$\ce{Cu + 4H+ + 4NO3- -> NO + 2H2O + Cu^{3+} + 3NO3-}$$
$$\ce{Cu + 4HNO3 -> NO + 2H_2O + Cu(NO3)3}$$

So does this compound $\ce{Cu(NO3)3}$ actually exist? or have I done a mistake.


texts: Can you measure an IR spectrum of a sample inside a glass vial?

texts: If I have a sample of some compounds dissolved in water inside a glass vial (let's say quartz). Would it be possible to get a usable measurement through this glass vial without too much absorption by the glass itself?


texts: In considering basicity (particularly of amines), often I find included with the compound a pKa. I understand that the higher the pKa of the conjugate acid, the stronger the base. But when the pKa is listed below a table of bases (for instance the wikipedia page for LDA – 36), does that refer to the pKA of the compound itself (LDA) or the protonated form?


texts: What do γ (gamma) and λ (lambda) mean in organic chemistry?

texts:
From the Wikipedia entry on Cyhalothrin:
Pyrethroids such as cyhalothrin are often preferred as an active ingredient in agricultural insecticides because they are more cost-effective and longer acting than natural pyrethrins. λ-and γ-cyhalothrin are now used to control insects and spider mites in crops including cotton, cereals, potatoes and vegetables.[5]
Lambda-cyhalothrin
Cyhalothrin gamma.svg
λ-cyhalothrin (racemic)
Compounds
Lambda: λ-Cyhalothrin
(RS)-α-cyano (1RS,3RS): Cyhalothrin
Gamma: γ-Cyhalothrin

Gamma-cyhalothrin[6] and lambda-cyhalothrin1 are the active ingredients in the current commercial products based on cyhalothrin. Both are cyanohydrin esters of cis-3-[(Z)-2-chloro-3,3,3-trifluoropropenyl]-2,2-dimethylcyclopropanecarboxylic acid. All of the insecticidal activity is due to the proportion of absolute stereochemistry (1R) in the mixture.[7] The active isomer of deltamethrin, (1R)-cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylic acid, has the same stereochemistry.
Cyhalothrin and deltamethrin acids.
γ-cyhalothrin (a single chiral isomer) is indeed twice as active as λ-cyhalothrin on a weight-for-weight basis. The latter is racemic and contains the (1R) and inactive (1S) isomers in equal amounts.

I have tried and tried on my own to find out what lowercase gamma and lowercase delta could mean here, but I can't find an answer...
Also what does,   AND Enantiomer mean?  Or,   A.N.D. Enantiomer?


texts: Why is it vital that atoms in the same sample are all given the same charge? Mass spectrometry

texts: When being tested in the spectrometer why is it vital that the atoms in the same sample are given the same electrical charge e.g all are c+1 or all are +2 etc


texts: Angle of Light Source for Absorbance Spectroscopy

texts:
I apologize if this question is stupid, but have been puzzled by it for a few days. Say I have a spectrometer measuring in the visible light range and we're looking to measure the absorbance on a solid material. In lab examples I've seen and read, the light source is placed on one end of the sample and the spectrometer on the other end. so the light passing through goes into the spectrometer. But what if you have a sample around 3 feet away from you. Could you place the light source next to the spectrometer and focus it on the sample then use a collimating lens in an attempt to see what was absorbed or not?

Once again, I apologize if this is a stupid question, I feel like I am missing some fundamental points of this process here.


texts: Safely lowering bleach pH without chlorine gas?

texts:
According to Eurekalert, by lowering the pH of household bleach (e.g., by adding vinegar or citric acid), we can increase $\text{[HOCl]}$ and consequently greatly improve the disinfecting capabilities of the bleach itself.

However, doing so could technically liberate chlorine gas, either through hypochlorous decomposition
$$ \ce{4H+(aq) + 4OCl- (aq) -> 2Cl2(g) + O2(g) + 2H2O (\ell)} $$
or mere comproportionation
$$ \ce{2H+(aq) + OCl- (aq) + Cl- (aq) ->  Cl2(g) + H2O (\ell)} $$
(depending on how the bleach was originally made) and so, mixing bleach and acid seems to be contraindicated everywhere else on the internet.

However, the authors of that link also suggest

  ... first diluting one cup of household bleach in one gallon of water and then adding one cup of white vinegar.

So then does that make it safe? Wouldn't chloroacetic acid formation also be a concern?


texts: What are the oxidation states in Borohydride (BH4-)

texts:
The CRC Elecrochemical Series and the solution to our exercise suggest that the oxidation states of borohydride are -V for Boron and +I for Hydrogen.

Since H (2.2) is more electronegativ than B (2.0), I would have expected the oxidation states to be +III for B and -I for H.

What am I missing here?

The solution to our exercise lists this (WARNING: it turned out that the solution was wrong):

And the CRC Elecrochemical Series lists this (also suggesting -V for B):


texts: Diastereoselectivity in synthesis problem (4 stereocenters)

texts: Why is the particular diastereomer the major product of the sequence starting from racemic enone? I know that hydroboration is syn, therefore the arrangement of ring junction H atom and OH group. Why is one of the methyl groups anti and one syn with respect to the H atom and OH group?


texts: Acetic(vinegar) and citric acid as the rust remover

texts:
I tested, separately, acetic and citric acids for cleaning steel parts. After 24 hours I have moderate results for acetic acid, and good results for citric acid. But in both cases, rust doesn't disappear fully.
I have two question:

If I mix two these acid, do I get the synergy?
Is there another acid which easy to buy?

P.S. I'd like to get clean iron without gray protective coat, like rust remover from auto parts shop.


texts: Is there radioactivity at absolute zero?

texts:
Theoretically, will a radioactive material still be radioactive at absolute zero? What would happen at the lowest realistic temperatures we have ever achieved?

Will radioactivity stop at absolute zero, since it is a nuclear phenomenon and nuclear motion slows down as we approach absolute zero (and theoretically stopping entirely at absolute zero)?


texts: Why do Electrons leave the Zinc in a Galvanic Cell

texts:
What induces  electrons to leave the atoms around the part of the zinc metal in a solution to travel up along that zinc metal and above the solution, through the wire and to the copper metal and reduce the copper ions in that solution.

Is it a result of the positive metal ions in a 'sea of electrons' being attracted to the negative ions of the solution making the electrons surrounding them leave, are the electrons repelled by the electrons in the solution or do these electrons 'sense' the copper ions on the other side waiting to be reduced and flows towards them?

I'm just not sure what prompts them to leave in the first place if the positive copper ions are not directly in contact with the zinc.


texts: Why are DOM lithiations sometimes conducted at −78 °C and othertimes conducted at elevated temperatures?

texts:
I'm looking specifically at n-butyllithium. I've noticed a number of lithiation reactions are conducted at −78 °C, whereas I've encountered papers conducting these reactions at elevated temperatures, up to 60 °C or 70 °C in some cases, under an inert atmosphere of course.

Is there a particular reason for lowering the temperature in some cases and not in others? Does it relate to minimizing side reactions of other groups in the molecule, or does it primarily have to do with stability of the ending lithium reagent at various temperatures? If the latter, does having multiple directing groups assist in stability?


texts:
Firstly, let me state that I'm no chemist. My specialty is in thermally applied coatings such as electric-arc metalizing.

During the course of my career I've always been presented with vague warnings to use "proper" ventilation to prevent hydrogen buildup within a contained area when spraying Al alloys.

Could someone please explain the process that creates hydrogen gas when arcing between two Al electrodes?

Also, what would the "proper" ventilation be? Would dry dust collection/ventilation suffice or would wet collection methods be required? Would this same reaction occur when using other alloys commonly used in thermal deposition processes?


texts: Is it a redox reaction if the oxidation state of the element has changed only in one of the products?

texts:
I’m not sure on which elements to compare to ensure that this is a redox reaction:

$$\ce{2 H2SO4 (aq) + 2 NaBr (s) -> Br2 (l) + SO2 (g) + Na2SO4 (aq) + 2 H2O}$$

I’m trying to indicate whether this involve oxidation/reduction. I’m looking at the oxidation state of $\ce{S}$.

What do I compare $\ce{H2SO4}$ with: $\ce{SO2}$ or $\ce{Na2SO4}$?

I tried both. Oxidation state of $\ce{S}$ in $\ce{SO2}$ is $+4$ and in $\ce{Na2SO4}$ is $+6$. One of them tells me it’s reduced, and the other tells me that no redox reaction is happening.

Which do I compare with and why? I’m not sure.


texts: Splitting of $d$ orbitals when ligands approach central metal ion

texts:
In my high school chemistry book, it is written that when ligands approach the central metal ion (transition metal ion) to form dative bonds, the $3d$ orbitals split into two: two which are in higher energy level and the other 3 in lower energy orbital...

One thing that doesn't make intuitive sense to me is that why 3 orbitals move to a lower energy level... if the ligands repel the electrons in the $3d$ orbitals, how can some of the orbitals possibly lose energy and be at a lower enrgy state than they were currently at before...


texts: Why absorption/transmission spectroscopic data is normalized?

texts:
A typical data processing step for acquired absorption/transmission data is normalizing, i.e. stretching the curve such that it is bounded between 0 and 100%.

However, the absorption/transmission curve changes with the density and thickness of the sample. Moreover, absorption is a non linear phenomena (for example Beer–Lambert law), so I would expect that the relative height of the various peak would not remain constant across several samples of the same material.

Why, therefore, is it justified to normalize acquired spectroscopic data? Why not present data with original abs./trans. values, while providing details about the sample itself (for example thickness)?

In addition, how can spectroscopy be quantitative if the relative height of the peaks changes with illumination/thickness/density/etc.?


texts: Why are we not getting the most stable product in Aldol condensation?

texts: The picture above is from my class notes. I am familiar with the mechanism of both acid and base catalysed Aldol condensation. I also understand the reason why KCP was told as the major product in base catalysed Aldol condensation. But we know that Aldol condensation is reversible throughout so shouldn't TCP product be major all the time?


texts:
In several pictures that I have seen of buckminsterfullerene and graphite (such as below), each carbon is bonded to only 3 other carbons, so it only forms 3 covalent bonds.

I asked my teacher about this and he says that each carbon only make 3 bonds and has a lone pair. These lone pairs are de-localised hence, that is why buckminsterfullerene is able to conduct electricity.

However, I am doubtful about this as how can a lone pair on an atom be de-localised. Would the electrons be in their orbitals, and not be able to freely move around the compound. I try searching the internet for any information, but there is no mention on how many bonds each carbon atoms makes.

I am guessing that there is alternating double bonds between each carbon so that each carbon has 4 bonds. It is these pi bonds which along the compound that makes it a  hyper-conjugated compound. This would explain why buckminsterfullerene and graphite are able to conduct electricity. Am I correct?


texts: What's the order of oxidising strength of the oxyacids of Chlorine?

texts:
What I have been told is that the acidity of the four oxyacids of Chlorine increase in the order $\ce{HOCl} < \ce{HClO2} < \ce{HClO3} < \ce{HClO4}$.

I have also been told that the oxidising strength goes in the reverse order. In my knowledge acidic strength should increase with oxidising strength. Where am I going wrong?

For your reference, the Ka values of the acids are as follows:

$\ce{HOCl} = 2.9 \times 10^{-8}$
$\ce{HClO2} = 1.1 \times 10^{-2}$
$\ce{HClO3} = 5.0 \times 10^2$
$\ce{HClO4} = 1 \times 10^3$


texts: I have a little problem with my paper about Mn superoxide dismutase. On this picture we have "B" behind the 3 OH ions, I really don't understand what is this. Where is this "B" from? Please, help me, my lecture will not accept my work today.


texts: Difference between basicity and reducing character

texts:
My understanding of basicity and reducing character:

Reducing character is the ability of a substance to reduce something else. So it itself must get oxidized. Since $\ce{BiH3}$ has a large radius, it will loose hydrogen atoms easily. Hence I conclude $\ce{BiH3}$ has more reducing character than $\ce{NH3}$.
Basicity is how easily can the compound give up hydrogen atoms/electrons.

Now I end up thinking basicity and reducing character are the same thing. And that $\ce{BiH3}$ should have more basicity than $\ce{NH3}$. But, this is not the corrrect answer.

So what's the difference between reducing character and basicity?

On mostly all Google searches I find that reducing character is directly proportional to basicity. But that doesn't say why they are different in the first place.


texts: Why are most atoms solids or gases but not liquids at room temperature?

texts:
Of all the elements of the periodic table, "most" elements with valences of four or less are solids, with most of these being either "metals" or "semiconductors."

On the right hand side of the periodic table, most of the elements are gases at room temperature.

There are only a "handful" of elements that are liquids (at room temperature). The one I can think of is mercury, and maybe there are one or two others that I have missed. Is there a reason why there are so few?

The reason I'm asking is because I expect the qualities of elements to fall on a spectrum. 1)At low temperatures, I expect a lot of solids. 2) At high temperatures, I expect a lot of liquids or gases. At room temperature, most items are solids (case 1). A fair number are gases (case 2). But few are the "intermediate" (liquid) case. Why is that?

The gist of the other question is, what qualifications cause an item to be a solid, liquid or gas at room temperature. My question is, why are these "qualifications" distributed as they are, in a seemingly "bipolar" manner? It would be like asking, why at a certain university, most GPA's are around 3.0, the second most around 4.0, but there are very few 3.5s (the intermediate case).


texts:
People that do rock climbing and weightlifting usually use magnesium carbonate on their hands to decrease slippery hands.

I would like to know how can someone that buys MgCO3 can really be sure it's magnesium carbonate and not another thing.

Is there a simple test people could do at home?


texts: I remember my Physical Chemistry Professor saying that very tiny negative Kelvin temperatures have been achieved on the quantum level. Is this true?


texts: Belousov-Zhabotinsky reaction: questions about rate determining step, k and activation energy

texts:
In one of our lab courses, we performed a variation of the BZ reaction, the experimental procedure is outlined below:

Experimental Procedure

10 mL of 3.0 M $\ce{H2SO4}$ was added to test tube T1.
Test tube T1 was placed on a stand and immersed in the water bath maintained at 35 °C
5.0 mL of 0.25 M $\ce{KBrO3}$ was added to test tube T2.
2.5 mL 0.02 M $\ce{Ce(NH4)4(SO4)4}$ in a 1.0 M $\ce{H2SO4}$ aqueous solution was added to test tube T3.
5.0 mL 1.0 M $\ce{CH2(COOH)2}$ was added to test tube T4.
Test tube T2 and T3 were added to test tube T1 and then the contents were swirled.
Test tube T1 and T4 were put into the water bath for 10 minutes.
While test tube T1 was still in the water bath, the contents of test tube T4 was put into test tube T1 and the timer was started.
Changes were observed while the tube T1 was vigorously shaken in the water bath.
The length of the induction period was recorded.
The reaction was allowed to oscillated 10 times, and the length of the period of oscillation was recorded.
The experiment was repeated at $\pu{40 ^\circ C},~\pu{45 ^\circ C},~ \text{and}~\pu{50 ^\circ C}$.

Also, here's the data set that I obtained:

Now, based on the instructions in our lab manual I plotted the following curves:

Now, my questions:

The manual instructs us to calculate activation energy using the period of induction and the period of oscillation from the Arrhenius plots above, which I calculate as $\pu{69.3 kJ/mol}$ (oscillation period) and $\pu{51.4 kJ/mol}$ (induction period).
But in doing so, we utilise the fact the $k = \frac{1}{\mathrm{period}}$ (i.e., $\ln(K)$ corresponds to $\ln(\frac{1}{\mathrm{period}})$. We were just given this information with no explanation. I can intuitively guess that for a first order reaction $k$ has the dimension $\mathrm{s}^{-1}$, but is there a stronger reason for making this selection?
I would guess the rate-determining step occurs during the induction period (since it is the slowest), but then the activation energy is lower. I would think that the energy barrier of the rate-determining step should be higher. Am I seeing a relation where none exists?
I noticed that the period of the reaction changed when the reaction mix was stirred more vigorously (temperature  and starting concentration being the same). Is that possible? If that is the case, then does that mean that the period isn't a reliable measure?


texts: How can I find the eutectic point of gallium and aluminum?

texts: I've been interested in liquid metals for a while, but I've stayed away from mercury for obvious health reasons. I have a sample of gallium and I've seen a liquid metal mixture of gallium and aluminum. I'd like to make this myself, and I want to achieve the lowest melting point I can, but I can't find much information on the eutectic point of these metals. Is there a way I can calculate it?


texts:
The book asks me to find the oxidation state of nitrogen in the compound below (the structure is not the one given in Wikipedia for HN3):

To find the oxidation state using Lewis structure, I have to compare the electronegativity of the bonded atoms and assign the bonding electrons to the more electronegative atom. Then, the difference between the number of electrons in element state and bonded state will give the oxidation number.

Here, the bonding electrons of nitrogens bonded with a double bond will stay in between both the atoms will not be assigned to both. The $\ce{N-H}$ bonding electrons will be assigned to $\ce{N}$. What about the two $\ce{N-N}$ bonding electrons?


texts: What would be an appropriate way to clean up equipment contaminated with ethidium bromide?

texts:
I want to clean up some old equipment that was used to visualize nucleic acids with ethidium bromide. It's a UV table, built from glass and metal (stainless steel, I assume).

Ethidium bromide is generally considered scary in a biological lab (probably because most stuff there is pretty harmless), but there seems to be a lot of controversy about the actual danger.

What would be an appropriate way to clean this? I'd simply wipe the whole thing with paper towels and some ethanol and dispose of them in the chemical waste. Would that be sufficient?


texts:
In the picture that I have uploaded, I have read that the given compound is chiral.

But on drawing the sawhorse structures (for better visualisation), I feel like the compound is symmetric about a plane that could bisect both OH and Cl.

What is it that I'm thinking incorrectly?


texts: Why does the Michaelis-Menten constant decrease in the presence of non-competitive inhibitor?

texts: Non-competitive inhibitors don't bind to the active sites of enzymes. However, in the presence of non-competitive inhibitors, the Michaelis-Menten constant is found to decrease. Why is this so?


texts: Convert an image of a chemical structure to a ChemDraw file?

texts: Is there a way to convert a bitmap (JPG, PNG) image of a chemical structure to a ChemDraw file so that you don't have to draw a structure you find in a paper yourself?


texts: What are some ways to predict that a double replacement reaction will occur?

texts:
For instance, say:

$\ce{2KOH + Pb(NO3)2 -> 2KNO3 + Pb(OH)2}$

How would I even go about beginning to predict this?


texts: Carboxyl groups are acids that comprise a carbon double bonded to an oxygen and single bonded to an oxygen-hydrogen. The one oxygen gets the two electrons it wants (so to speak) from the double bond with the carbon, the other gets the two it wants from the bond with the carbon and the hydrogen. The hydrogen is also satisfied by its bond with the oxygen. The only electron stealing opportunity I can see is in the polarity of the hydrogen. Is that what the acidic property of carboxy groups consists in?


texts: Differentiating Al2O3 from SiO2 using chemical methods

texts: I have granules of $\ce{Al2O3}$ and granules of $\ce{SiO2}$. They look almost identical and I have mixed them up. Is there a simple chemical test that would allow me to differentiate between these granules?


texts: Variable oxidation state of transition metal ions

texts:
Transition metals can form stable ions with different oxidation states. But I am confused why doesn't only the most stable state exist. Let me clarify my question more:

$$\ce{Ti^{2+} -> Ti^{3+} + e^-} $$
With $E^0 = +0.5~\mathrm{V}$.

This just shows that $\ce{Ti^{3+}}$ is more stable. So my question is that why doesn't $\ce{Ti^{3+}}$ only exist in its most stable form?


texts: Why does increasing number of salt bridges increase voltage of electrochemical battery?

texts:
In an experiment, I set up a cell with lead nitrate (w/ lead electrode) and zinc sulfate (w/ zinc electrode), with a salt bridge containing potassium nitrate.

I observed that by increasing the number of salt bridges, the voltage measured increased. However, given what I know about electrochemical cells, I can't work out why. I initially thought it would have no effect on the voltage/potential difference.


texts: How would I grow my own and build functional solar cells? I've read and researched that they're mostly a crystal structure of something like silicon. I would assume I'd be able to grow my own crystals and sandwich this in a process of some sort with a p-type and n-type, etc.


texts: Why transition metal catalyzed [2+2]cycloaddition reactions allowed?

texts:
As you know, cycloaddition reactions which (4n)π electrons are involved in such as [2+2]cycloaddition are forbidden in normal organic reactions, but transition metal catalyzed [2+2]cycloaddition reactions are allowed.
I think the d orbitals of transition metals play important roles in the reactions, but I cannot understand how they work.
I found this article on the Internet, and the reaction is explained.
https://pubs.acs.org/doi/abs/10.1021/ja00734a016#


texts: Determining weight-percent methanol in water from specific gravity and temperature

texts:
The company I'm working with uses a fuel mixture of methanol and water. We use a hydrometer to measure specific gravity, in order to test the composition of fuel received from our suppliers. To determine the weight percent of methanol we use a chart provided by The Methanol Institute that correlated specific gravity to weight percent at different temperatures.

Click image for full-size PDF

I'm trying to build a spreadsheet for operators, suppliers, and customers to measure the specific gravity at an arbitrary temperature, enter the temperature and specific gravity measured, and get the weight percent without having to interpret a chart.

In order to do this, I need some sort of formula to calculate the weight percent for any input of specific gravity and temperature  (within a reasonable range anyways).

Here are the approaches I've tried so far:

Fitting a line to the plot above and creating an empirical model. There isn't sufficient resolution in the plot to do this with any useful level of accuracy.
Finding the source information used to create this plot. I called The Methanol Institute and they have no idea where the plot came from, saying it's been used for years and they don't know a source or have any other related data. I tried calling Methanex, a major supplier of methanol which has published similar tables and charts, but I haven't gotten through to anybody so far.
Finding other sources for water/methanol mixes. One of my coworkers found a (printed) table with weight percent methanol in a water/methanol mixture for a wide range of temperatures and covering the weight percent range we're interested in. I scanned and OCR'd the table and created a plot. The table appears to lack sufficient resolution to develop an empirical model as well; with only 3 significant figures the lines appear wavy when plotted:

Calculate using the specific gravity of pure methanol and pure water at a given temperature, then calculate the specific gravity of the mixture using an adjustment for the $\Delta V_{mix}$. This approach seems to work fairly well, but I could only find data for the change in volume due to mixing for 25 °C (page 12 of this PDF from Methanex). This table is "calculated from density and specific volume data" but no additional information is given. A reference table at the end of the document does have the specific volume of methanol at various temperatures, but nothing about change of volume when mixed with water specifically.

I searched at length for methanol/water excess molar volume data. So far I've found data from various sources, but only at 20 and 25 °C, not over a range of temperatures.
Derivation from thermodynamics. I've pulled out my thermo textbook and am reading about equations of state and thermodynamics of mixing. I think given enough work I could probably derive a model from the thermodynamics approach, but I would prefer something based on actual measurements, since theory doesn't always match reality.

The actual question:

Is there an existing resource that would accomplish what I need?
If not, is there a source of good data on water/methanol mixtures at different temperatures that I might be overlooking?
Otherwise, is there a good source of data for excess molar volume over a range of temperatures (at least 18 – 30 °C, preferably wider) that I might be overlooking?
Is there a different approach I should consider?


texts: What are the microstates of the triplet oxygen molecule?

texts: I am trying to understand molecular term symbols of oxygen molecule. Everywhere I looked, it is claimed that the molecule has 6 microstates, three of them are singlet, and three of them are triplet. Now I can draw the diagrams for the singlet states with no problem, but I am struggling to find the tree triplet configurations. According to my microstate matrix there should be a triplet state with a total spin multiplicity of zero - how is this possible?


texts:
Following up the question Formation of a stable hydrate.
I understand that for cyclopropanone the change in hybridization is the reason for stabilization of hydrate since it relieves the angle strain.
So, can this be further be given as a reason to state the hydrate of 2‐indanone (structure below) will be stable? I suppose upon hydration the angle will change from 120° to 109.8°, bringing the angle closer to that of a pentagon that is 108°.

I am confused if this is appropriate or if it's true. If it's wrong, please explain.
P.S. After going through the comments I understood by considering keto-enol tautomerisation that hydration might not at all be favourable.


texts: How does dilution affect result of titration of jam?

texts:
We currently do some pH adjustments of jams (target pH of 3.2) using citric acid, however, when there is a large difference between the starting pH and the target pH this can be quite a time consuming process (add to vessel, mix, take sample, repeat).

It's been a long time since I've done chemistry, but I believe that because the pKa of the citric acid is close to the target pH and the jams are a complex mix of buffering agents that it isn't easy to come up with a simple formula for the amount to add (in fact, I observe, even at a similar starting pH, the amount of citric acid required varies a  lot).

My idea was to titrate citric acid into a sample of jam that has been diluted with distilled water for easier mixing:

Jam @ 50% dilution
Citric Acid dissolved at a ratio of 1:9 in distilled water

My thought is that if I keep taking samples and titrating the citric acid with the diluted Jam that I will get a nice correlation between the titration amount and the amount of citric acid required to add to the batch.

My question is:

Will this produce a nice correlation?
Is it possible to do this theoretically?

Thanks,


texts:
Consider $\ce{PCl3}$, $\ce{CH2Cl2}$, $\ce{HCN}$, and $\ce{SiO2}$. Which of these molecules are polar substances?

I appear to be lacking on the concept of "polar substance". I was just studying about Lewis structures and this question popped up in the book, but I'm not quite sure how is this related.

I think that a chemical bond is polar when one atom is more electronegative than another. But my basic understanding tells me that a chemical bond is non-polar only when the two atoms are the same (like $\ce{F-F}$ or $\ce{O-O}$). But all the above options have different atoms, so the answer would be "none", which is clearly wrong because that's not one of the options.

How can I tell if a molecule is polar or not?


texts: What does the molecular orbital scheme of beryllium chloride and hydride look like?

texts:
Beryllium is a somewhat fascinating element since it is the only member of the second group that behaves somewhat non-metalish and, e.g. forms a somewhat covalent chloride and a covalent hydride.

In an answer to a different and unrelated question, I tried guessing what the bonding picture of $\ce{BeCl2}$ would be. Given the monomer’s linear shape, I was inclined to assume something that introduces a four-electron-three-centre bond, which has the nice side-advantage of allowing beryllium to contribute to bonding orbitals using its s orbital only. However, I would guess that the more traditional picture would include two $\mathrm{sp^2}$ type bonds to the neighbouring chlorines and then a nonzero amount of π backbonding making the MO similar to that of $\ce{CO2}$.

What does the actual, calculated MO scheme of $\ce{BeCl2}$ look like; what does $\ce{BeH2}$’s look like, how do they compare and what can we learn from them concerning the bonding properties of beryllium?


texts: How can I test fruits and vegetables for certain insecticides?

texts:
I live in Turkey and I don't feel safe eating the fruits and vegetables that I enjoy that are plentiful here.  After reading this article, I have been washing all fruits and vegetables with water and vinegar mixture, but I am not sure if this is sufficient.

As stated in said article fruits and vegetables exported to the EU (European Union) from Turkey have been returned to Turkey for having unacceptable levels of certain insecticides; particularly Chlorpyrifos (banned for causing hormonal problems in humans) and Methamidophos (hazardous carcinogenic chemical).

The article mentioned that the returned goods could not be traced after their return to Turkey and most likely were sold and consumed domestically.  Although Turkey has the same laws as the EU for banning and restricting these chemicals, these are obviously not enforced.

I need help in figuring out a practical method of testing for these chemicals.  In the EU, RASFF- the Rapid Alert System for Food and Feed is a key tool to ensure the flow of information across borders to swiftly react when risks to public health are detected in the food chain.  Perhaps the RASFF tools are practical and cost effective or maybe there is even a more practical detection technology or method.

I tried to find what specific tools and methods the RASFF uses to detect these pesticides but their website does not openly reveal these details.


texts:
Using radio waves to heat, and electromagnetic fields to contain....could methane be heated to much higher temperatures than via simple oxygen/combustion, thus producing a much higher specific impulse for, say, a rocket engine?

Not talking plasma drive temps here (millions of degrees), but several thousand degrees above normal combustion temperature.


texts: Creating energy profile diagrams for publication

texts:
Is there automated software to create energy profile diagrams like the ones below?

One could use something like Illustrator or Inkscape, but they aren't automated, are expensive (Illustrator), are difficult to use, and wouldn't be practical for anything with more than a dozen energy levels. These diagrams don't look like they were hand-drawn, but I could be mistaken.

Ideally, it would be written in Python, but something in LaTeX or TikZ would be workable as well.

More specifically, I think this could be improved upon quite a bit.


texts: Why molar volume takes range of values along triple line whereas the temperature and pressure are constant along this line?

texts: In the P-V-T surface the triple line is the line parallel to P-V plane on which three states of matter are in equilibrium. Temperature and pressure are same at all points along the triple line. But we know that the value of one of the three state variables(pressure, temperature, molar volume) will be specified if other two state variables are specified. If we specify two state variables then the third state variable can't take range of values. But along the triple line for specific temperature and pressure there is range of values for molar volume. Can anyone explain why? Maybe I am missing something obvious.


texts: What force causes an electron to jump from say Na to Cl?

texts:
Every explanation I can find says something like: valence electrons in metals have low ionising energies and non-metals ''want'' to complete their valence shell.
But I can't seem to get my head around the ''wants to complete it's valence shell'' force.
Take a neutral sodium atom and a neutral chlorine atom separated by some distance. Now move them closer until the valence electron of sodium makes the jump. What force did it feel if chlorine is neutral ? My only explanation is that the valence electron induces a dipole on the chlorine atom. In other words the presence of the valence electron pushes the electron valence orbital of chlorine away slightly. The positive nucleus of the chlorine atom is not pushed away due to shielding by the other shells in chlorine. Now that the valence shell of chlorine is pushed away slightly the valence electron of sodium begins to feel a slight attraction to the chlorine atom despite it being neutral overall. It is now a dipole. At some point the force of attraction between the valence electron of sodium and the chlorine atom is stronger than to the sodium atom and makes the jump.
Is this a reasonable explanation as to why the electron makes the jump or is it something else entirely ?


texts: What is the dataset with the largest number of molecules?

texts:
In computational chemistry we often apply techniques to all molecules of a "dataset". Recently it was asked which dataset contains the largest molecules, and a user accidentally  misinterpreted this as asking for the dataset with the largest number of molecules: Datasets of Large Molecules

This question now gives that user an opportunity to give their answer here.


texts: How to find equilibrium constant in reactions which have a limiting reagent?

texts:
If in the following reaction

  $$\ce{H2 + I2 <=> 2HI}$$

  the initial concentrations of $\ce{H2}$ and $\ce{I2}$ are $\pu{1 M}$ and $\pu{5 M}$, respectively, and at equilibrium $x$ moles of each have combined. Then what will be the $K_\mathrm{c}$ for the reaction?

What I think is that the $K_\mathrm{c}$ will not change because it does not depend on the initial concentrations of reactants and depends only on the stoichiometric equation, but the one thing I can't reason out is that those extra $4$ moles of $\ce{I2}$ should also have an affect on its equilibrium concentration (since those $4$ moles are still present in the vessel) and thus affect $K_\mathrm{c}$.

Please help me find the correct explanation for the aforesaid question.


texts: According to Wikipedia, vitamin C (ascorbic acid) "may also act as an antioxidant against oxidative stress," and is "widely used as a food additive, to prevent oxidation."  But acids are, by definition, oxidizing agents, so how is it that ascorbic acid is used to prevent oxidation?


texts: First step in a reaction between an acyl chloride and sodium acetate in acetic acid

texts:
What would the first step be in a reaction between acyl chloride and sodium acetate in the presence of acetic acid?

I'm a bit confused because I'm not quite sure which step would occur first. I was thinking that perhaps the sodium acetate will first attack the carbonyl carbon, but I'm also wondering if it would be possible that sodium acetate would first react with acetic acid, turning the latter into an anion that could react with the acid chloride forming an anhydride.


texts: Express the maximum work from a voltaic cell

texts:
The net cell reaction of an electrochemical cell and its standard potential is given below:
$$\ce{ Mg + 2Ag+ ->Mg^{2+} + 2Ag} \ \ \ \ \ \ \ \ E^\circ=3.17\:\mathrm{V}$$
The question is to find the maximum work obtainable from this electrochemical cell if the initial concentrations of $\ce{Mg^{2+}}=0.1\ \mathrm{M}$ and of $\ce{Ag+}=1\ \mathrm{M}$.

The solution just uses the Nernst equation to find the potential at this concentrations and uses $\Delta G=-nFE$ to calculate the Gibbs free energy change which is then equated to the maximum work obtainable.

But this is just the work obtainable per mole at this concentration only. As soon as the reaction proceeds, the concentration change and so does the value of $\Delta G$ per mole and therefore the maximum work obtainable is different for different concentrations.

Therefore, to find the maximum work obtainable, shouldn't we first calculate the equilibrium constant of this reaction (I calculated it to be $K_c=1.89\times10^{107}$), then the equilibrium concentrations(which is probably $\ce{Mg^{2+}}=0.6\ \mathrm{M}, \ \ce{Ag+}=0.178\times10^{-53}\ \mathrm{M}$) and then use something like:
$$
\int_{\mathrm{in}}^{\mathrm{eq}}\Delta G* \mathrm{d\,M}
$$
where $\Delta G$ is per mole and the $dM$ is a small amount in moles that the reaction proceeds at that concentration.

Please help me verify my method and to proceed further.


texts: We know that both solids and liquids can exhibit metallic luster. I wonder whether there is a gas that when filling a transparent envelope (such as a glass tube) would make it appear with metallic luster?


texts: What to say 'one mole of C atoms or one mole of C molecules?

texts:
What to say 'one mole of C atoms or one mole of C molecules in CO? Please point out if I am wrong here
As we know,
one molecule of CO = one mole of CO molecules = 6.223 X 10^23 number of CO molecules
If I split one molecule of CO, we get one C and one O. Here are my questions, What to say these ''one C and one O" one mole of C atoms and one mole of O atoms or ''one mole of C molecules and one mole of O molecules'' or just like above like ''one C and one O''?
Could you clarify it, please? I am confused


texts: Measure the concentration of lactose in dairy products

texts:
I would like to measure the concentration of lactose in various dairy products : milk, cheese, yoghourt...

How is it done in labs ?
How can I do that using cheap equipments ?

Thanks


texts: If the human body consists of 60% water why can't we put out fire with our body?

texts: I have often heard of people being burned at the stake, but if the body is 60% water shouldn't the fire just be put out?


texts:
I am currently taking a course where we are exploring nitrate concentrations in water samples. We are using a UV-Vis Spectrophotometer and have created a calibration curve in the first part of the experiment.

Now in the second part of the experiment we need to measure the absorbance rates and use the calibration curve produced in the first part of the experiment to find the nitrate concentrations.

I expect that I need to multiply the concentration obtained from my calibration curve by the dilution factor used during the determination of the absorption rate, however, I would like to get this confirmed and understand better how this works.


texts: What makes scorpions glow under UV light?

texts:
What substance (or class of substances) is responsible for the neon blue-colored fluorescence we observe when we shine UV light on scorpions?

Do note, I want to know what substance makes them glow and not why they glow... the latter being more suited for the Bio.SE.


texts:
The flow chart is indicative of a compound with a silver cation, because $\ce{Ag+}$ reacts with $\ce{I-}$ to form yellow $\ce{AgI}$. Since $\ce{Ag+}$ does not form a hydroxide complex, it forms the brown $\ce{Ag2O}$ precipitate with excess $\ce{NaOH}$ solution. With $\ce{BaCl2}$, $\ce{AgCl}$ white precipitate forms. When excess $\ce{NH3}$ solution is added to that mixture, the soluble complex ion $\ce{Ag(NH3)2+}$ forms.

So, I can choose between answer choices A and B. However, I am not sure which cation is correct. The answer key says the answer is A, but I am not sure why, because both form white precipitate with $\ce{BaCl2}$.


texts:
A question asks whether C4 in 3-butyne-2-one can act as a nucleophile, electrophile, or acid (it can be more than one). The answer is that it can be both electrophilic and acidic.

The acidity makes sense, it's a terminal alkyne, sp orbitals stabilize the negative charge on the conjugate base.

The electrophilicity I don't quite understand. I can write a resonance structure that puts some positive charge on C4, analogous to an alpha-beta unsaturated carbonyl compound, but it looks bizarre. I know ketenes are a real thing, but is  this resonance structure a real contributor? Is there another explanation for the electrophilicity?

Google searches for alkynone, ynones, etc. yielded mostly peer-reviewed literature that's above my understanding.


texts: What home chemical can I use to make droplet lens?

texts:
I'm very interested in making homemade droplet lens, I want to know what home element can I use to cook them.

Here's a video showing the process, with no further information:

https://www.youtube.com/watch?v=NQLWS5j8gB4

And a research paper about it:

http://www.opticsinfobase.org/boe/fulltext.cfm?uri=boe-5-5-1626&id=284161


texts: Does water vapor in the air oxidize copper?

texts: My friend is installing copper pipes in his house, which is going to be in a humid area, and he says that copper will only be oxidized by the air and the excess water vapor in the humid air won't affect it. However, it is to my understanding that since water vapor is $\ce{H2O}$, which contains oxygen, there will be more oxidation occurring, and thus more corrosion to the pipes because of more oxygen present in the air. Is this correct?


texts: For a given period, why is the boiling point of the halogen greater than that of the noble gas?

texts:
The boiling point of bromine, a halogen, is $\pu{58.8^\circ C}$, while the boiling point of krypton, the noble gas in the same period as bromine, is $\pu{-153.4 ^\circ C}$.

I thought that the larger the atomic radius of an element, the more loosely the electrons would be held by the nucleus. So it would be easier for the atom to develop an instantaneous dipole, strengthening the London forces between the atoms of the element, and increasing the boiling point of the substance.

Krypton has a larger atomic radius than bromine. Using my reasoning from above, I thought that the boiling point of krypton would be higher than that of bromine. However, bromine actually has a higher boiling point than krypton.

Why is this? And where is my reasoning incorrect?

Complete data for reference: notice that the boiling point of a halogen is always higher than that of the corresponding noble gas, and the difference increases down the group.

$$
\begin{array}{|c|c|c|}\hline
\text{Period}&\text{Halogen boiling point} (\pu{^\circ C})&\text{Noble gas boiling point} (\pu{^\circ C})\\\hline
2&−188.11&−246.046 \\\hline
3&−34.04&−185.848 \\\hline
4&58.8&−153.415 \\\hline
5&184.3&−108.099 \\\hline
\end{array}
$$


texts: Is an acid (just) a proton donor and if not, what is the correct definition of an acid?

texts:
Why is acid called proton donor?

On the internet, I found:

  Acids are substances that can donate $\ce{H+}$ ions to bases. Since a hydrogen atom is a proton and one electron, technically an $\ce{H+}$ ion is just a proton. So an acid is a 'proton donor.'

However, my teacher said that it is not fully correct. If this is the case, then what's the correct definition of an acid?


texts:
Does steric hindrance affect Brønsted basicity?

I understand that basicity is a thermodynamic quality. Not a kinetic factor. So it doesn't matter if it takes a million years for the proton to reach the site of basicity; time is nothing in thermodynamics. We only care about the initial and final state. So this suggests to me that steric hindrance does NOT affect Brønsted basicity

In addition, the hydrogen proton is quite small. So I wouldn't expect it to be particularly sterically hindered by anything (unless we're in solution and the proton is heavily solvated). Still, once the proton reaches the site of basicity, it's reached it, and if I understand thermo correctly, thermo doesn't deal with anything in the middle of the energy graph. Only the points on the two ends.

Also it would be nice if one could comment on the difficulty of this problem in general. Just curious. Personally I think it's a fascinating problem. (On the other hand I'm not the one actually doing the problem).


texts: If propane with specific parameters were to combust in open air, what is actual volume of CO2 produced

texts:
Lets say we have a sample of propane gas having a volume of 2.70 L at standard room temperature and 1.75 atm. This gas is exposed to our air. The equation that governs this reaction is:

$mC_3H_8 + xO_2 + 3.76xN_2 \rightarrow yCO_2 + zH_2O + dN_2 + eO_2$

Here $m,x,y,z,d$ and $e$ are coefficients. I want to find out what the volume of carbon dioxide given this information. The trouble I'm having is finding out what pressure the air is and I strongly suspect that I would use the sea level or 1 atm and the volume of nitrogen and oxygen with which propane reacts with.


texts: Is this home-made pesticide from cigarette butts and battery acid safe?

texts:
An old friend once told me that a good way to kill bugs in my garden was to soak lots of cigarette butts in water to make a gallon of the brown liquid. Then add one ounce of battery acid and mix well. He said to spray it on the garden and wait two to three weeks before harvesting because it would take that long for the mixture to become Niacin. I thought it sounded cool but never tried it.

Now 40 years later I would like to, but I want to know if this is really true or would it ruin my vegetables? It's been 22 years since my chemistry classes and tried to make sense of this link.
It seems like the nicotine/acid thing would become neutral, but again, I have forgotten so much that I'd feel safer running this past a few more knowledgeable folks first.


texts: How to plot the wave function after a Hartree-Fock calculation?

texts:
I have written a code in Mathematica and have obtained the final energy of the hydrogen molecule. I have used Gaussian basis functions for this calculation. Now I need to plot the ground state wave function. How can I do so? I just know that the ground state wave function is defined as
\begin{align}
  \psi_i &= \sum_{\mu=1}^k C_{\mu i}\phi_{\mu} &
  i &= 1, 2, 3, \dots, k,
\end{align}
where $\phi$ is a basis function. However I don't know how to obtain an expression for the ground state wave function.


texts: Why Zn has highest ionisation enthalpy in 3d series?

texts:
Zn which has the highest ionisation enthalpy in 3d series.The reason given in my textbook is:

  The value of zinc is higher because it represent ionisation from 4s level.

This is not correct because for every 3d element ionisation is from 4s orbital. The explanation I found for this is from this site is:

https://www.chemguide.co.uk/atoms/properties/ies.html

  Increase in nuclear charge outweigh the electron electron repulsion of 4s electrons rendering Zn an higher ionisation enthalpy than Cu.

This seems like a probable explanation but if Zn has higher ionisation enthalpy than Cu due to its increased nuclear charge.Why can't Zn have smaller atomic radius than Cu due to its increased nuclear charge which can decrease the size of the atom. But experimentally it has been found that Zn is bigger in size than Cu.

So why does Zn has the highest ionisation enthalpy in 3d series?

TEXT SOURCE:NCERT textbook (chapter:d and f block)


texts: Why is phenyl shift preferred over methyl shift in cumene hydroperoxide reaction?

texts:
In the cumene process, which converts cumene to phenol and acetone, there is a step where cumene hydroperoxide undergoes acid-catalyzed rearrangement:

(Image source: Wikipedia)

Why does the phenyl shift happen preferentially? The methyl group is smaller and should have a higher migratory aptitude.


texts: What is the role of dichloromethane in the ozonolysis / Criegee oxidation?

texts: Why is $\ce{CH2Cl2}$ used in ozonolysis of alkenes and alkynes? What role does it play in the reaction? Is dichloromethane a common solvent for organic reactions and used for its inertness, or is it particularly used in ozonolysis reactions? If it is the latter case, how does it enhance the ozonolysis reaction?


texts: Need help with an IR spectrum (polymer identification)

texts:
I have been given an unknow polymer and I have to identify it.

DSC measurements showed no glass transition (which means it's below room temperature) and a melting temperature at around 100-120°C. So, I thougth it was a polyethylene. But then, the IR spectrum showed some bands that I didn't expect.

The only thing I'm sure about are the peaks at around 2900 being C-H streching.

Maybe the large band between 3200-3400 is an O-H bonded? At 3500 cm-1 a N-H ? 1370 I really don't know...

I don't find any corresponding polymer. Could it be a copolymer ? Or an impurity ?

Could you help me please ?


texts: So, as part of an experiment, I plan to make a diprotic basic buffer. For a monoprotic basic buffer, I used the standard combination of Ammonia and Ammonium Chloride. However, how can I make a diprotic basic buffer using commonly available reagents? If possible, could you also explain how the buffer behaves in the presence of an acid/base?


texts: When we say "the energy in a system" (in chemistry) do we mean the energy stored in the chemical bonds in the compounds present in that system?

texts: Is it the energy stored in the chemical bonds of the compounds present in a system, that we refer to as the energy in/of a system ?


texts: Can't you form a ring from almost any number of sides from carbon?

texts: Recently, we have been learning Chemistry in my physics class at school. We learned that Carbon is one of the elements that has the most variety in the compounds it can formed, being able to form four covalent bonds. This got me thinking- I know you can form Carbon into hexagonal rings- graphite does this- but shouldn't you be able to form almost any kind of polygon from carbon, with each one double bonded to the two next to it?


texts: Can anyone tell me what reaction is this?

texts:
I came across this reaction, but I have no idea what reaction is this. Can anyone please tell me?

What will be the products?

My first guess is that a carbene will be formed which will attack on the alkene, but I don't know what to do after that.


texts: Why does aluminium chloride react with water in 2 different ways?

texts: Aluminium chloride has 2 different reactions with water, depending on whether a small amount or an excess of water is added. One produces a solution of hexaaquaaluminium ions whereas the other produces a ppt. of aluminium hydroxide And HCl gas. Does the 2nd reaction occur due to the reaction 1 first occurring followed by vaporisation of the solution due to the heat given out?


texts:
I'm currenty wondering what the correct naming scheme for the following molecule would be:

Is this called "2,N,N-trimethylpropan-1-amine" or "2-methyl-N,N-dimethylpropan-1-amine". In other words, do you group the substituents attached to the N with the other substituents.


texts: How do you know if SN1 orSN2 reaction occurs when it is not so obvious?

texts: For instance, when you have a primary halide with a weak nucleophile, do you think that the reaction mechanism would be SN1 or SN2, neither or would it even be both, like sometime leaving group can leave by itself creating carbocation and nucleophile because it is late later attack in second step. Same when you have a tertiary halide and really strong nucleophile and polar aprotic solvent (which we know facilitates SN2 rxn). I am not sure how to think of the process. Like when it comes to primary and tertiary halides,  does the substrate nauture determine mode of mechanism from the get go, with no input of the strength of nucleophiles, or type of solvent. Or do nucleophiles and type of solvent have a role in determining whether sn1 or sn2 would occur also?


texts:
To extract essential oils from plant matter (amongst other purposes), steam distillation is often used. I've seen a lot of different glassware setups for this. I've sometimes seen them broken into two categories:

Internal steam distillation
External steam distillation

Here's my (admittedly shaky) understanding of each:

Internal

With internal steam distillation, you have one boiling flask containing plant matter and liquid water. You simply boil the mixture and send the gas to to the condenser.

External

With external steam distillation, you have two flasks. One contains water only. You heat this one and route the steam into the second flask. The second flask contains a mixture of water and plant matter. The steam from the first flask combines with the liquid mixture in the second flask. Optionally, the second flask also has a heating mantle. The output of the second flask then goes to the condenser.

Differences?

What is the effect of using one or the other setup? External is substantially more complex, so I can't imagine it would be used if it didn't offer some advantages in some circumstances. When would you use external, and why?


texts: Software to predict equilibrium products in the ideal gas phase

texts:
I'm interested in software packages that can answer the following kind of question:

If I mix 30mol% $N_2$ and 70mol% $H_2$ together at 2 bar and 2000C, what is the equilibrium composition after all reactions have reached equilibrium. Assume all reactants and products are ideal gases.

This is a relatively straightforward calculation. All that is required is knowledge of standard Gibbs Free Energies of formation and specific heat capacities for each species which may be formed. Of course, the challenge is guessing which species may be formed - here an obvious candidate is $NH_3$, but it is certainly possible that the formation of other species could lead to a lower value of the Gibbs Free Energy. A software package with a large database of standard Gibbs Free Energies and ideal gas heat capacities would be very useful here - you could simply select to search over all chemicals which you suspect may be formed, or instead you could minimise the Gibbs Free energy over 'all substances in the database' (at least those composed of the available chemical elements - $N$ and $H$ in this case.)

Does anyone know of any software packages (open source or otherwise) which could do these calculations?


texts: Why is data about wavelengths of different colors and the visible spectrum in general so different in different sources? On Wikipedia, the numbers differ by up to $\pm\mathrm{30~nm}$.


texts: I have came across the following statement : "the oxidation state $+II$ is stable for the elements of the alkalin earth metals" , the same is true for the elements of the first group , i've looked for a possible explanation and heard that it has a relation with the charge densities of the elements , if that's true what is that relation ? otherwise , what could explain the oxidation states for each of the groups in the periodic table ?


texts: What is the ionic equation for reaction of potassium permanganate with potassium iodide?

texts:
The half equation for the reduction of the permanganate would be

$$\ce{5e- + 8H+ + MnO4- -> Mn^2+ + 4H2O}$$

But with regards to the iodide, I am very confused. I have seen some sources say that $\ce{I-}$ is oxidised to $\ce{IO3-}$ in this reaction, and others saying that it is oxidised to $\ce{I2}$.


texts: Does Reduction Potential affect rate of electrolysis

texts:
I am currently doing a project on electrolysis, and I was wondering if the reduction potential (ie. $E^0$) will affect the rate of electrolysis. In other words, across different cells with differing $E^0$ values, is there a trend in the rate of electrolysis of these cells? Why or why not? I have seen other similar questions but all were talking about the ease of discharge/selective discharge of ions, which is not what I am looking for.

Thanks!


texts: Does there exist a molecule of formule XαYβ where X and Y are elements that are also found in molecule XγYδ?

texts:
I am not a chemist, but I will be explaining chemistry to some third-graders. I want to give the example of how different things can be made of the same parts, but arranged differently. My "real world" example is a car and a motorcycle. The car has an engine and four wheels, but we can create a different vehicle with an engine and only two wheels: we get a motorcycle. Does there exist a molecule composed of the elements $\ce{X}$ and $\ce{Y}$, where $\ce{X}$ and $\ce{Y}$ can form a different molecule when the quantities of $\ce{X}$ and/or $\ce{Y}$ atoms are different?
I was hoping to use carbon and hydrogen because the children have already heard me use those words, and $\ce{CH4}$ is a gas that will make them laugh when I tell them where it comes from. But the only $\ce{CH2}$ molecule that I could find is this, which is too complicated and unfamiliar to explain. I would prefer molecules composed of the common elements hydrogen, oxygen, carbon. I would like to avoid molecules of elements that are commonly found in their elemental state such as gold, iron, or silver as at this stage I want to reinforce the idea that we cannot see molecules with the unaided eye. I might introduce the idea that a molecule (and macromaterial) can be composed of a single element later, if this lesson goes well.
For purposes of discussion, a molecule can be defined as "a discrete body composed of atoms". There is no need to address quantum chemistry, as the target audience is a third-grade classroom.


texts: What fraction of hydrogen in air results in an explosive mixture?

texts: I would like to know if there is documented evidence of the quantity of hydrogen to air that must be present in the mixture to risk explosion or flame.


texts:
Some days ago, before buying a chocolate I read the ingredients and saw that it contains a natural emulsifier. A Google search didn't reveal anything about of what the emulsion formed is, do you have any idea?

The general composition of chocolate:

  The main components in milk chocolate is cocoa butter, sugar, and milk
  powder.

Then, a concrete example:

  Hershey’s chocolate is made of sugar, chocolate, cocoa butter, cocoa
  processed with alkali, milk fat, lactose (milk), soy lecithin, PGPR
  (emulsifier), vanillin, artificial flavor, and milk.

This is taken from The Chemistry of Chocolate on ChemistryIsLife.com

I continue wondering what the emulsion is formed by.


texts: Sugar cube is filled with liquid (coffee), only if corner is sinked for few millimeters

texts:
Sorry for quite stupid question, but I could not find answer for it (perhaps my question is wrong).

I noticed one thing about sugar cubes. When I sink one corner of cube in coffee, just for few millimeters, after a few seconds it's already turning brown (filled with coffee, so to say). Another thing, if I sink it for a short period of time and take it out, coffee liquid stops spreading, if I sink it again it continues.

Why this is happening?


texts: Determination of brominated aromatics by 13C and 1H NMR spectroscopy

texts:
How can I identify 4-bromoazobenzene, 4-bromoazoxybenzene, and 4,4’-dibromo-$\ce{N,N}$’-diphenylhydrazine products using $^1\ce{H}$ and $^{13}\ce{C}$ NMR?

I’m really confused by the general shape of NMR peaks of aromatic protons. I want to distinguish each product from the other products, knowing that the three products are synthesized starting by the reaction of 4-bromonitrobenzene with sodium borohydride.


texts: Home made dispersion/solution with detectable >0.1μm particles

texts:
Sorry for the possibly wrong terminology. I'm not a chemist and I'm not a native English speaker.
Please edit the question as needed. Thank you.

Is it possible to buy or prepare a dispersion with the following properties?

the particles should be >0.1μm in size, for example 0.11μm - 0.2μm
there must be a way to detect them - even in a small amount (colour, taste, chemical reaction with something else, ...)
it mustn't be a "glue"; it must be possible to flush them completely away with water or something else readily available
it mustn't be a toxic or corrosive substance
the dispersion (or components to prepare it) should be readily available (drugstore, grocery etc.)
the total price shouldn't be higher than $20 (I know this difficult with prices different in every country - this is just a guideline)

Why do I need it?
There's a very slight chance that a Sawyer Micro Squeeze Water Filter might have been exposed to a below zero temperature and might have been damaged by frozen residual water.
The manufacturer says there's no way to test the filter functionality in that case and a new filter should be bought instead. I wonder if this is really needed or there's a way to test the filter at home.


texts: What causes the iridescent colour in laboratory grown bismuth?

texts:
Artificially grown bismuth crystals are arguably magnificent, as seen in the image below:

Image source: Minerals.net

The website states that:

  They have hopper-like growths in pseudocubic crystals and are usually coated with chemicals to prevent tarnish, thus maintaining the silver-white color. Sometimes the coating gives a colorful effect on the bismuth.

What coating gives the colourful iridescence? and what chemical processes cause the colourful iridescence to occur?


texts:
In IUPAC naming double bonds take preference over an alkane chain of any length, right? So the above should be named as 2-ethylnon-1-ene.

However, when I verify with chemdraw it gives the answer as 3-methylenedecane. I cannot seem to find any mention of double bond side chains as alkylene anywhere on the internet... Is this common nomenclature, and if not why would chemdraw name it as this?


texts: Can 1,2-dioxetanedione (active ingredient in glow sticks) undergo stimulated emission (and thus form a laser)?

texts:
In common glowsticks, diphenyl oxalate reacts with hydrogen peroxide, forming 1,2-dioxetanedione. The dioxetanedione is unstable, but direct decomposition to carbon dioxide is a forbidden transition, so this can only happen in a reaction with another molecule. If the other molecule is a suitable fluophore dye, the dye molecule will become exited and then emit a photon of light. (The color depending on the fluophore used.)

Some types of lasers make use of forbidden transitions: atoms or molecules are brought into an excited state such that the transition to the ground state is forbidden and thus slowed down. This causes the exited state molecules to collect, forming a population inversion. The excited molecules can then undergo stimulated emission in a resonance cavity, producing the laser effect.

Now my question is if 1,2-dioxetanedione can also be made to undergo stimulated emission if the glow stick chemical reaction takes place in a suitable optical resonance cavity. (It looks to me like it should, but my chemistry knowledge is not enough for this.)

Alternatively, if the 1,2-dioxetanedione cannot undergo stimulated emission, could a suitably chosen dye molecule?


texts: Looking for a theory predicting conductivity values of electrolytes at higher concentrations

texts:
I'm looking for a theory to calculate the electrical conductivity of electrolytes, namely $\ce{NaCl}$ and tartaric acid ($\ce{C4H6O6}$) dissolved in water, depending on their concentration.

The only equation I could find was the one derived from the Debye-Hückel theory, which I read works great for 1:1 electrolytes like $\ce{NaCl}$ (not sure about tartaric acid 1:2 electrolyte), but only until about 0.1 M.

The concentrations in my case vary from 0.2 M up to 4.0 M.

Is there a theory I can use to calculate conductivities in that range, or is the Debye-Hückel theory the only one?


texts:
Suppose we have a redox reaction and we want to see in what direction the reaction is spontaneous. We do this by comparing the standard reduction potentials of the sub-reactions available in the main reaction and say if
$$E^\circ = E^\circ_\text{Oxidizer}-E^\circ_\text{Reducer}>0$$
 then the reaction is spontaneous in the direction mentioned otherwise in the reverse direction. The same result can be obtained by comparing the standard oxidation potentials. However, as every spontaneity has its root in the second law of thermodynamics I am eager to see how the spontaneity of a redox equation in a given direction can be checked based on thermodynamics.

So basically how can we derive the condition
$$E^\circ = E^\circ_\text{Oxidizer}-E^\circ_\text{Reducer}>0$$
 for spontaneity of a reaction from the fundamental thermodynamics laws?

To clarify the question better let me add that I already know that the second law for a common chemical reaction yields into the condition $$dG \le 0\,,$$ my question is about to find the condition
$$E^\circ =E^\circ_\text{Oxidizer}-E^\circ_\text{Reducer}>0$$ from that inequality. Also let me add further that I even already know that the electric work equals $-n F E^\circ_{\text{cell}}$ but I cannot justify for myself why $\Delta G$ is equal to this work. (Note. the electric work is an internal work not crossing the boundaries of the system, it is not the work of the system, and if it was then at best we had $\Delta G=W_{\text{max}}$ but the inequality $\Delta G\le 0$ no longer hold.)


texts: How can I create a graph of a titration curve (acid-base, strong or weak, not something specific), with an equation or a function. In other words, what is the equation that describes such a curve that could be used in graphing software to recreate the curve without actually needing any experimental values? Also, if they exist, what are the parameters of the function (Molarity? Volume? Etc.)


texts: Why does the activation enthalpy of ester hydrolysis increase with an increase in alcohol-chain length?

texts:
(Particularly concerning acid hydrolysis) Is there some sort of chemical reason as to why with increasing alcohol-chain length, there is also an increase in the minimum energy needed to cause the ester bond to break?

Does the molecule as a whole become more stable because of the large -R group of the alcohol section of the molecule, for example?

(I am thinking of esters like methyl and ethyl ethanoate).


texts: Why is cyclopentadiene anion is aromatic but cycloheptatrienyl anion is not?

texts: I just can't seem to figure this out. The cyclopentadienyl anion (1) is aromatic, but the cycloheptatrienyl anion (2) is not, though its cation (3) is. Why?


texts: I have a question regarding net ionic equations. In a solution, sodium fluoride and hydrochloric acid are mixed together. The "correct" net ionic equation is shown below. However, how can this actually BE a net ionic equation, since none of the ions change state (all aqueous)?


texts: Why is the composition of a liquified vapor the same as that of the vapor?

texts:
In Organic Chemistry Lab Techniques (Nichols), I found this diagram.

I understand that when going from Point $a$ to Point $b$, the composition becomes richer in the more volatile component (component A).

However, why does condensation of the vapor at Point $b$ not change the composition? Shouldn't the condensate of a vapor be richer in the less volatile component (the reverse of vaporization), by the principle of microscopic reversibility?


texts: Why does mixing two solutions decrease the concentration of the solutes?

texts:
The irreversible liquid reaction

  $$\ce{A + B -> C + D}$$

  follows an elementary rate law and is carried out
  isothermally in a plug flow reactor (PFR). The volume of the PFR is 500 litres. The concentration of $\ce{A}$ is $\pu{2 mol L-1}$ and concentration of $\ce{B}$ is $\pu{2 mol L-1}$ before mixing. The volumetric flow rate of each stream is $\pu{5 L min-1}.$

  The streams are mixed immediately before entering. The reaction rate constant at $\pu{20 °C}$ is $\pu{0.05 L mol-1 min-1}$
  and $E = \pu{20 kcal mol-1}.$ (Note: gas constant $R = \pu{1.987 cal mol-1 K-1})$

  Find conversion at $\pu{40 °C}.$

This is what I had:

From the solution given the $c_{\ce{A},0}$ used is $\pu{1 mol L-1}$ which is after mixing. Need some clarification on this. Why is it not $\pu{2 mol L-1}$ before mixing?


texts:
This question was given by my chemistry professor, but I doubt that this question is not correct.

Following the lewis definition of the acid, any molecule or atom acts as a acid if it accepts an electron and according to Inorganic Chemistry by Weller CO is a good $\pi$ acceptor, then how it can be weak pi-acid ligand? In fact, CO is a poor $\sigma$ donor.

What am I missing?


texts: What is the most "important" resonance structure of SCN⁻?

texts:
Numerous online references say that $\ce{SCN-}$ has two resonance structures:

I am wondering why this structure is not also possible?

I expect structure 3 to be rare because of the high formal charges, but shouldn't it be included as a possible resonance structure?

Furthermore, there is disagreement about whether structure 1 or structure 2 is more common. I would expect structure 2 to be more common because the negative charge is on the more electronegative N atom. However, this worksheet says that structure 1 is more common. On the other hand, this video says that structure 2 is more common. Which should it be?


texts: How can ionic bonding in lanthanides occur without valence orbitals available for overlap?

texts:
I've recently been taught that the 4f orbitals in lanthanides are "core-like", supposedly meaning they have radius smaller than the 4d orbitals, therefore they are not available on the outside of the atom to form covalent bonds with ligands. The lecturer then went on to say that, therefore, the bonding of lanthanides to ligands is entirely ionic.

It is my understanding that a bond is deemed ionic when there is a large electronegativity difference between the two atoms, i.e. the bonding molecular orbital is near-identical in energy to the atomic orbital of the more electronegative atom, as shown below for sodium fluoride:

However, if this is the case, how can lanthanides form any bonds if their valence orbitals are not available? Surely orbital overlap with the ligand is still required to form a molecular orbital, even if the resulting orbital is ionic in nature?


texts: I have heard that electrons absorb or eject photons when transitioning from one orbital to another. Is this correct? Can atomic nuclei eject photons?


texts: Why don't decomposition reactions form pure elements as products?

texts:
For example, if I had a reaction like this:

$$
\ce{NaHCO3 -> Na2CO3 + H2O + CO2}
$$

Why does it not break down all the way down to its elements?
What makes it form such "intermediate" products, stopping at water, carbon dioxide, etc.?


texts: Complex formation in water and Henry's law

texts:
I've been trying to solve the following problem for a while now.

Consider a mixture of two different gases ($A$ and $B$) for which Henry's law holds. When gas molecules $A$ and $B$ do not interact with each other in either the gas phase or in water, the amount of each that will be dissolved in water is determined only by its partial pressure and does not depend on the partial pressure of the other gas. However, let us now consider the case in which $A$ and $B$ form a complex $AB$
when they are dissolved in water:
$\ce{A(l) + B(l) <=> AB(l)}$
Let $x_i$ ($i$ = $A$, $B$, $AB$) be the mole fraction of the dissolved species, and let $K_{AB}$ be the equilibrium constant for the above equation:
$K_{AB} = \frac{x_{AB}}{x_Ax_B}$
Suppose that water ($V_l$ = $\pu{1.00 L}$) and a gas mixture are filled into a container ($V = \pu{2.00 L}$) at $\pu{25^\circ C}$. The
Henry coefficients of $A$ and $B$ are $1.0×10^4$
, and $\pu{2.0E4 bar}$, respectively, and $K_{AB}=500$. The initial partial pressures of each gas, $P_A^0$ and $P_B^0$, are both $\pu{2 bar}$.
1) Calculate the pressure of each
gas and the mole fractions of the dissolved gas molecules after the equilibrium is established.
2) Calculate the percentage of the mole fraction of dissolved gas $B$ relative to that found in question 1)
when the initial partial pressure of gas $A$ is increased to $\pu{10 bar}$.

I'm having trouble coming up with the right equations to cope with the multiple unknown variables. What I have come up with so far is the following.
$n(A)_{g,i} = n(B)_{g,i} = \frac{P^0V}{RT} = \pu{0.08072 mol}$
$n(\ce{H_2O}) = \frac{1000}{18.016} = \pu{55.51 mol}$
$x_A = \frac{P_A}{k_{H,A}}$
$x_B = \frac{P_B}{k_{H,B}}$
$x_{AB} = K_{AB}\cdot \frac{P_A}{k_{H,A}}\cdot\frac{P_B}{k_{H,B}}$
$P_{f,y} = \frac{n(y)_{g,f}RT}{V}$
$P_{f,y} = k_H x_y \approx k_H\frac{n(y)}{n(\ce{H_2O})}$
$\frac{n(y)_{g,f}RT}{V} = k_H\frac{n(y)}{n(\ce{H_2O})}$ (1)
I'm not sure how to involve the effects of the complexation equilibrium on the moles of dissolved gas $A$ and $B$, respectively. Normally I would calculate the number of moles dissolved using the following formula derived from equation (1) ($y$ is any chosen gas):
$n(y)_l = \frac{n(H_2O)n(y)_{g,i} RT}{n(H_2O) RT + k_{H,y} V}$
But this doesn't take into account the equilibrium formed when $A$ and $B$ are dissolved in water and form the complex $AB$.


texts: Why is ionic strength (mu) calculated differently for these 2 examples?

texts:
In the following examples; I don't understand why $\ce{Na_3PO_4}$ is a much more complicated process when calculating $\mu$ compared to $\ce{NaH_2PO_4}$ and $\ce{Na_2HPO_4}$. Specifically, I don't understand how to determine which species to include in the $\mu$ equation. All of the examples I've come across just behave just using water and the original species at most. What is more confusing also, is why doesn't the $\ce{NaH_2PO_4}$ and $\ce{Na_2HPO_4}$ include the concentrations and charges of their conjugates as the last example with $\ce{Na_3PO_4}$ does.Thanks for any help!!! Here is the work:

$0.1000M$ of each reagent to start.

$\ce{NaH_2PO_4}$

$$\text{Ignoring} ~H^+ \text{and}~ OH^-. [C] << 0.1M$$
$$\mu = \frac{1}{2}\sum([Na^+](+1)^2 + [H_2PO_4^-](-1)^2)$$

$$\mu = \frac{1}{2}\sum([0.1M](+1)^2 + [0.1M](-1)^2)$$

$$\mu = 0.1000M$$

$\ce{NaH_2PO_4}$

$$\text{Ignoring} ~H^+ \text{and}~ OH^-. [C] << 0.1M$$
$$\mu = \frac{1}{2}\sum([Na^+](+1)^2 + [H_2PO_4^-](-2)^2)$$

$$\mu = \frac{1}{2}\sum([0.2M](+1)^2 + [0.1M](-1)^2)$$

$$\mu = 0.3000M$$

$\ce{Na_3PO_4}$

Without using Quadratic (which is just to keep things simple):
$$[OH^-]=0.044M$$
$$[PO_4^{3-}]=0.056M$$
$$[HPO_4^{2-}]=0.044M$$
$$[H^+]=\frac{K_w}{0.044M}=2.27*10^{-13}M$$
$$\mu = \frac{1}{2}\sum([Na^+](+1)^2 + [PO_4^{3-}](-3)^2+[HPO_4^{2-}](-2)^2+[H^+](+1^2))$$
$$\mu = \frac{1}{2}\sum([0.3M](+1)^2 + [0.056M](-3)^2+[0.044M](-2)^2+[2.27*10^{-13}M](+1^2))$$
$$\mu=0.5120M$$


texts: Why can you blow bubbles in milk but not hot cocoa, which is milk based?

texts:
My daughter is asking this question and I’m assuming it’s something related to the cocoa added to milk but don’t know what change is happening molecularly and why it would affect the bubbles. Thanks!

Let me know if there is a better place to ask this question!


texts:
The reason given me in my book is that it's stable due to steric relief.
The answer given on quora said "there is a lot of angle strain."

What exactly is steric relief ?

Can anyone help me elaborate how these points are contributing to the answer.Also what is the minimum angle to provide strain so that geminal diols are stable


texts: Why do vinegar and other acids remove rust?

texts:
I have started a project on restoring a very rusty knife. I had used vinegar to remove the rust. A question dawned on me: why does vinegar remove rust? So being the thoughtful person I am, I googled it. Unfortunately, Dr. Google could only provide me with what it is doing (which I already know).

But what I really want to know is: what chemical reaction causes the rust to disappear?


texts: Can ethanol be oxidized by hydrogen peroxide?

texts:
Is it possible to oxidize ethanol to acetic acid with hydrogen peroxide and if yes then
under what circumstances? I tried it in room temperature but either concentration was too small (of hydrogen peroxide(3%)) or I couldn't quite precisely read the the results of the universal indicator. I also tried heating it up, but it didn't change anything. The color stayed the same (of indicator). Can someone please explain me if the mistake was in my experiment (if the reaction can happen in room temperature) or the reaction needs some specific catalyst or other conditions.
The reaction would be:

\begin{align}
\ce{\underset{(ethanol)}{C2H6O} + H2O2 &->
  \underset{(aldehyde)}{C2H4O} + 2H2O}\\
\ce{\underset{(aldehyde)}{C2H4O} + H2O2 &->
  \underset{(acetic acid)}{C2H4O2} + H2O}
\end{align}

Or the reaction without the middle part (since aldehyde will try to oxidize faster then ethanol) would be:

$$\ce{C2H6O + 2H2O2 -> C2H4O2 + 3H2O}$$


texts: Ester vs ether links: Why are archaeal cell membranes more resistant to high temperatures and acidity than bacterial and eukaryotic membranes?

texts:
The phospholipids composing the cell membranes of eukaryotes and bacteria contain ester links between the glicerol and the fatty acids. Archaeal membranes, instead, are composed of phospholipids containing ether links between a glicerol and an isoprene chain:

My microbiology teacher explained that these differences, mainly the ester vs ether links, were determinant to maintain the archeal membranes stable in environments with high temperatures and acidity, but she didn't go into much detail on why. I would like to know the specific chemical reasons why.

(Disclaimer: Considering I'm interested only in the organic chemistry involving this situation, and not in specific archeal phisiology or biology in general, I found it adequate to post this question here in the "Chemistry" cathegory.)


texts: What are the known atomic oxygen species?

texts:
I'm interested in chemical reaction mechanism with more exotic particles. The Wikipedia page seems to imply that the normal atomic oxygen is $O(^3P)$, is that right?

I also came across $O(^1D),O(^1S),O(^5P)$ and some longer strings like $O(3S3s)$. What are the atomic oxygen species, or at least these which we can expect to see in the parts per millions range or a little below, in oxydation processes specifically? How to know which I left out?


texts: Is there a simple field test for heavy water?

texts:
Thought experiment

Given two glasses of water, how would one detect which glass contains heavy water, and which contains potable water without using complicated laboratory equipment?

Something like the way a piece of litmus paper (yes, it is laboratory equipment and easily available to the layman at that!) may be used to test whether a solution is an acid, or alkali.


texts: If heavy metals bind to sulfur why isn't sulfur used as a safer way to chelate them?

texts: I was wondering about sulfur as an alternative life-threatening chelators. Why isn't sulfur used as a chelator if heavy metals have an affinity for it?


texts: Can rate constant for forward reaction be equal to rate constant for backward reaction?

texts:
For a particular reaction, can we have
$K_c = 1$?

My confusion arised when I was studying the effect of temperature on $K_c$ . I see that the temperature must affect forward and backward rate constants, differently for a reaction so that it changes $K_c$ (which is ratio of the two rate constants). So I thought for a reaction with $K_c$ equal to one, both the rates must be equal, so both will get equally affected by temperature, and thus no change in $K_c$ , or does it have something to do with the Arrhenius equation?

I know that there is a lot of lacking in my intuition as I have just began studying Le Chatelier's principle and all the stuff. So a detailed explanation would be much welcome.


texts: Determining the mass of sodium sulfate that forms when reacting sulfuric acid with sodium hydroxide

texts:
I have come across simple problem in the chemistry book which I cannot solve. The question is below. I would appreciate if you have any solution to this.

Question:

  $3\ \mathrm{g}$ of $\ce{NaOH}$ are mixed with $4.9\ \mathrm{g}$ of $\ce{H2SO4}$. How much sodium sulfate $\ce{Na2SO4}$ will form?

(The answer is $3.55\ \mathrm{g}$)

Note: I have calculated it as $5.33\ \mathrm{g}$ of $\ce{Na2SO4}$ don’t know where I am mistaken. It doesn’t seem to be a typo in the question because I couldn’t solve other similar problems in other books wither. There is something I always miss.


texts: Does anyone know if the human gastic lipase has a quaternary structure? If not, why not? I can not seem to find this information anywhere.


texts: How the plate height is assumed to be the standard deviation?

texts:
Fundamentals of Analytical Chemistry book states that the  plate  height  can  be  thought  of  as  the  length  of  column  that  contains  a  fraction  of  the  analyte  that  lies  between  $L$  and  $L - \sigma$ [1, p. 870].
But what I know is that $H = \sigma^2 / L$ (At the retention time), so, how can plate height be equal to $L - (L - \sigma)$?
$H$ is the plate height. $L$ is the column length. $\sigma$ is the standard deviation.
Reference

Skoog, D. A.; West, D. M.; Holler, F. J.; Crouch, S. R. Fundamentals of Analytical Chemistry, 9th ed.; Brooks Cole: Belmont, CA, 2013. ISBN 978-0-495-55828-6.


texts: What is the minimum mass of iron(III) chloride required to be added until the dark blue precipitate first appear?

texts:
How do I solve this question?

  The presence of iron(III) ion is confirmed in a qualitative analysis by adding potassium hexacyanoferrate(II) ($\ce{K4[Fe(CN)6]}$) solution.

  A dark blue precipitate, iron(III) hexacyanoferrate(II) ($\ce{Fe4[Fe(CN)6]3}$), is formed.

  What is the minimum mass of iron(III) chloride (in grams) required to add to a $\pu{200 cm3}$ of $\pu{0.0010 mol dm-3}$ potassium hexacyanoferrate(II) solution until the dark blue precipitate first appears?

  solubility product of $\ce{Fe4[Fe(CN)6]3} = \pu{3.30 x 10^-41 mol^7dm^-21}$
  relative molecular mass of $\ce{FeCl3} = \pu{162.3 g/mol}$

  Choices:

  $\pu{1.35 x 10^-8 g}$
  $\pu{4.38 x 10^-7 g}$
  $\pu{5.48 x 10^-7 g}$
  $\pu{2.19 x 10^-6 g}$

This is what I came up with just now :

  $K_\mathrm{sp} = \ce{[Fe^3+]^4 [Fe[CN]6^4-]^3}$

  $\pu{3.3x10^-41}$ = $\ce{[Fe^3+]^4[0.001]^3}$

  $\ce{[Fe^3+]^4}$ = $\pu{3.3 x 10^-32 mol dm^-3}$

  $\ce{[Fe^3+]}$ = $\pu{1.35 x 10^-8 mol dm^-3}$

  Mass of $\ce{FeCl3} = \pu{1.35 x 10^-8 mol dm^-3 \times 0.2 dm^3 \times 162.3 g/mol}$

  = $\pu{4.38 x 10^-7 g}$

  I am still relatively new to this topic so I am not sure if I am doing this correctly. Any help will be appreciated. Thank you !


texts: Why ammonium salts can not undergo substitution

texts:
Why is ammonium salt, such as RNH3+, can not react with nucleophiles like HI to give RI and NH4+? The reaction is pretty much like the substitution of alcohol in acid condition.

In my opinion, NH3 (rather than NH2-) is a very good leaving group, so it can be substituted by good nucleophiles like I-. In order to prevent the resulting ammonia from attacking back, we can add more acids like HI to drive the equilibrium to the right direction.

I haven't found any signs of this reaction in textbooks, so I thought this reaction cannot happen. If it is a common reaction, where can I find more information? Thank you all in advance.


texts:
NaBH4 and LiAlH4 will be a source for the hydride ion and reaction will begin with addition of hydride by displacing the carbonyl group.

But I am not sure will it attack both the carbonyl or only one.
Moreover, Will it displace the chlorine at the bottom carbon?


texts: Chemical equilibria and changes in concentration

texts:
I learned that if concentration of reactants or products is changed, the position of equilibrium changes but value of $K_c$ remains the same.
This just does not make intuitive sense to me... I mean whatever concentration of reactants I start with does not matter, $K_c$ remains same....?

Also, can someone please elaborate the term position  of equilibrium


texts: How do the Bonding and Anti-bonding MOs of dx2-y2 sigma bonding with another dx2-y2 look like ? I mean to ask that if the sigma bond is along the x-axis then is the shape of the lobes along y-axis altered during the formation of the MOs.


texts: Pepto-bismol molar bismuth concentration

texts:
I want to measure the Bismuth molar concentration in the OTC drug "pepto bismol".

525 mg bismuth subsalicylate (C7H6BiO4) / 30 mL (17.5 mg/mL)
molecular weight 363.10054 g/mol

If I convert to mM (17.5 mg/mL / 363.10054 g/mol * 1000), I get 48.2 mM. However, this value seems very high. Am I missing something obvious?

I am sorry if this question seems basic to you. I can't find the answer anywhere else though. Thank you so much in advance!


texts: Does electrolysis of aqueous tin(II) chloride produce Cl₂, SnCl₄ or both?

texts:
When applying a current to an aqueous solution of tin(II) chloride, tin crystals grow from the cathode. However, I'm not sure about the anode. It seems like there are two possible reactions:

$$\ce{2 Sn^2+(aq) + 4 Cl-(aq) -> Sn(s) + SnCl4(aq)}$$

and

$$\ce{Sn^2+ (aq) + 2 Cl- (aq) -> Sn(s) + Cl2}$$

Online sources that I've found — including an educational lab and YouTube videos of the experiment being performed — give inconsistent answers. I'm thinking that both products are produced; if that is the case, how can I predict exactly how much of each will be produced? Can other factors, e.g. current, electrode material, pH change the results?


texts: What is the minimum distance of Rubidium and Iod ions in a centered cube?

texts:
I have a problem to visualize the following assignment:

What is the minimum distance between $\ce{Rb^+}$ and $\ce{I^-}$ ions if radius of  $\ce{Rb^+}$ is ${1.49\cdot10^{-10}}~\mathrm{m}$ and radius of $\ce{I^-}$ is ${2.17\cdot10^{-10}}~\mathrm{m}$ if they are arranged in centered cube?


texts: Reverse osmosis membrane used as an osmosis membrane

texts: I recently came across the so-called 'thin-film composite membranes'. They are build up of layers with one of them being semipermeable. As I'm not well versed in chemistry, I'm unsure, if these membranes can be used for standard osmosis too, or if their permeability-property is reliant on the exerted pressure i.e., they allow the flow of water just in one direction.