texts:
What happens when the above compound is mixed with D2O (deuterated water)?
As a result of tautomerism, I'd expect the 4H atoms, one alpha to carbonyl carbon, and three at gamma position; to be replaced with deuterium.

However, I'm not clear about the mechanism that'd be followed to achieve the same.

My thoughts:
The first step should involve formation of carbanion by abstraction of hydrogen gamma to carbonyl group. The carbanion is stabilised by extended conjugation, and has three resonance structures.

Now, how does the reaction exactly proceed? Could someone please provide a detailed mechanism, it'd be really helpful. Thanks a lot.


texts:
It's the amount of heat required for liquid ---> gas phase change of a substance at it's Boiling point.
But my question is, does providing energy equivalent to latent heat of vaporization to a liquid at a temperature below it's Boiling point (if you need, also assume above it's Freezing point) 'Evaporate' it?
eg. When water is kept inside a clay pot out in the Sun, we know a very small amount of water somehow seeps out through it's pores and 'evaporates' (if not vaporizes). Obviously the temperatures aren't even close to 373K(boiling point of water), but the water is spontaneously turning into steam. Because it's not boiling, but is simply evaporating which can take place any where below it's boiling point. But the point here is, 'how much' of the energy from the rest of water-pot system is entrapped in order to convert into a form that has got more energy than its predecessor.
Is it equivalent to only the amount of latent heat of vaporization or is it plus the amount of energy required to raise it's temperature upto it's boiling point.


texts: What are the practices to naming organic chemicals by abbreviations?

texts:
Is there a preferred method to writing organic chemicals by abbreviation?

I am finding it hard to decipher the methods I see in writing.

For example $\ce{EtOH}$ is ethanol, which makes sense, but $\ce{PhAc}$ is acetophenone, where the constituents appear to be backwards.

What about more complicated chemicals like 1,1-diphenylethanol, would $\ce{EtPh2OH}$ be considered appropriate, or maybe $\ce{Ph2EtOH}$?


texts:
The following question was given in NCERT Exemplar Problems (Class XII):

According to Wikipedia:

  In organic chemistry, the aromatic alcohols or aryl-alcohols are a
  class of chemical compounds containing a hydroxyl group (—OH) bonded
  directly to an aromatic hydrocarbon group, in contrast to the benzyl
  alcohol, where the hydroxyl group is bonded indirectly to an aromatic
  carbon atom.

But, I didn't understood the part: aromatic alcohols or aryl-alcohols (as aromatic alcohols are not always aryl alcohols).

Further, we know that aryl halides are compounds in which halogen group (-X) is directly attached to an aromatic ring. In the same way, aryl alcohols also mean that those compounds in which hydroxyl group (-OH) is directly attached to an aromatic ring.

Hence, according to my understanding, the answer should be (ii), but the answer given is (iii).

Where I am wrong? And, what is an aromatic alcohol?


texts:
When I notice that ferric chloride is sold as $40\%$ solution w/v, does it mean weight / volume?

Is it a matter of for example adding $40$g of ferric chloride crystals to a water solution where the total volume will then be $100$ml?

Or do I have to workout via the molar mass of $\ce{FeCl3}$ to water? How do I calculate the weight of crystals necessary to create a $40\%$ solution of $\ce{FeCl3}$?

Thanks

EDIT:

The system seems to think this is a homework question (whatever that is). If I divide $100$ml of water (so $100$g) by $40\%$, I get $40$g of $\ce{FeCl3}$. If I dissolve $40$g of $\ce{FeCl3}$ in $100$ml of water, will I get a $40\%$ solution of $\ce{FeCl3}$? And a total volume of $114$ml? ($\ce{FeCl3}$ is $2.9\frac{\mathrm g}{\mathrm{cm^3}}$, so $40$g is approx $13.8$ml)?


texts: Protonation of Carbonyl oxygen in Fischer Esterification

texts:
In the Fischer Esterification, why is it the acid's carbonyl oxygen getting protonated and not the hydroxyl oxygen? This protonation occurs in Step 1 of the mechanism below.

I read in some textbooks that this is due to the carbonyl oxygen being more neucleophilic and the hydroxyl oxygen. Why is this so?


texts: Constraint optimization of the linear H4 and H6 chain with gaussian

texts:
I want to optimize the linear hydrogen chain ($d_{\infty h}$, equal bond lengths) with gaussian 16.

Using z-matrix

# opt=z-matrix hf/sto-3g

H6 chain

0 1
 H
 H  1  r1
 H  2  r1  1  a1
 H  3  r1  2  a1  1  d1
 H  4  r1  3  a1  2  d1
 H  5  r1  4  a1  3  d1
Variables:
r1=0.9
Constants:
a1=180.0
d1=0.0

is not possible, since angles of 0° and 180° are not allowed.

 Error on Z-matrix line number      3:  angle Alpha is outside the valid range of 0 to 180.
 Error on Z-matrix line number      4:  angle Alpha is outside the valid range of 0 to 180.
 Error on Z-matrix line number      5:  angle Alpha is outside the valid range of 0 to 180.
 Error on Z-matrix line number      6:  angle Alpha is outside the valid range of 0 to 180.
 Conversion from Z-matrix to cartesian coordinates failed:

Using generalized internal coordinate optimization (GIC) module

#p hf/sto-3g
opt geom(AddGIC)

H4 chain

0 1
 H
 H  1  r1
 H  2  r1  1  a1
 H  3  r1  2  a1  1  d1
Variables:
r1=0.9
Constants:
a1=180.0
d1=0.0

R12(active)=R(1,2)
R23(active)=R(2,3)
R34(active)=R(3,4)
R23(modify)=R12
R34(modify)=R12

LinBend1H1H2H3(freeze)=L(1,2,3,0,-1)
LinBend2H1H2H3(freeze)=L(1,2,3,0,-2)
LinBend1H2H2H4(freeze)=L(2,3,4,0,-1)
LinBend2H2H3H4(freeze)=L(2,3,4,0,-2)

does not work either.

 ***** Axes restored to original set *****
 -------------------------------------------------------------------
 Center     Atomic                   Forces (Hartrees/Bohr)
 Number     Number              X              Y              Z
 -------------------------------------------------------------------
      1        1          -0.000000000    0.000000000    0.093021603
      2        1           0.000000000   -0.000000000   -0.205327093
      3        1           0.000000000    0.000000000    0.205327093
      4        1          -0.000000000   -0.000000000   -0.093021603
 -------------------------------------------------------------------
 Cartesian Forces:  Max     0.205327093 RMS     0.092025570
 Leave Link  716 at Fri Apr 24 15:09:36 2020, MaxMem=  1342177280 cpu:               0.4 elap:               0.1
 (Enter /usr/local_rwth/sw/gaussian/LINUX_emt64/g16.c01_bin_avx2/l103.exe)

 GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
 Berny optimization.
 NTrRot=    -1 NTRed=     6 NAtoms=     4 NSkip=    -1 IsLin=T
 Problem with coordinate system.

How can this be done?


texts:
In Atkins Physical Chemistry 10th edition in chapter number 10B it is given that within the Born-Oppenheimer approximation, the Schrödinger equation can be solved for the molecular species $\ce{H2+}$ but to simplify things and to obtain a method more readily generalizable to more complex species, we use the linear combination of atomic orbitals concept.

But my question is: how do we know that the wave function obtained from the linear combination obtained (say of two 1s orbitals of each atom) satisfies the Hamiltonian of this new system involving two nuclei? (The modified Hamiltonian is also given on the same page in the book).

Or do we need to make some iterative calculation as in the Hartree-Fock self consistent field method.

PS. I am a beginner so please try to keep the answer technically simple if possible.


texts: Full Valence Shell (Octet Rule) vs Formal Charge

texts:
When does formal charge have more precedence over the octet rule / an atom having a full valence shell when drawing structures?

When you draw $\ce{BCl3}$ for example, there are no double bonds - just three single bonds. Because of this $\ce{B}$ does not end up with 8 valence electrons. The explanation I have seen for this is that a double bond makes it so that the formal charge is undesirable. When drawing structures which has a higher precedence: formal charge or ensuring the atoms have full valence shells?


texts: Why rinse flask with distilled water when the flask will be used for storing aliquots of HCl for titration?

texts:
In an experiment for standardisation of NaOH with titration, the lab manual instructed students to rinse conical flasks that were supposed to store 1mL aliquots of hydrochloric acid with distilled water.

Won't the excess water dilute the aliquot? Why not rinse with the HCl solution instead?

Thanks in advance.


texts: Which kind of plastic material would be suitable for a clutch cover on a motorcycle transition?

texts:
I'm going to have an online machine shop build a part for me using a CAD drawing that I specify.

Typically, these parts are made of aluminium, but this manufacturer also mills parts out of these plastic materials:

Polypropylene (PP)
Polystyrene (PS)
High impact polystyrene (HIPS)
Acrylonitrile butadiene styrene (ABS)
Polyethylene terephthalate (PET)
Polyester (PES)
Polyamides (PA) (Nylons)
Poly(vinyl chloride) (PVC)
Polyurethanes (PU)
Polycarbonate (PC)
Polyethylene (PE)

Polypropylene, I know, is the plastic used in water bottles, so I know that is not what I want.

This fabricated part will be used for the clutch cover on a motorcycle transmission and will have a raised section that needs to be tapped to allow attaching a gear shifter to, like in the aluminium version below.

I'd like something rigid and strong. Plexiglass comes to mind, but there could be a better alternative that I am unaware of, as long as I am not getting into something exotic that would cost more than aluminium.

Could suggest a good plastic for me, which would need to be oil resistant and withstand typical engine transmission temperatures.


texts:
I was going through my chemistry book (RT Morrison and Boyd) and found a statement:

  " the collision frequency of isopropyl and n-propyl w.r.t. Chlorine atoms is the same."

Is it correct because I think the size will matter in this case while both have the same weight?


texts: Why does rock salt change colour when it's heated

texts: We heated rock salt for a chemistry lab and it changed from white crystally rock to brown rock and ash-like materiak on the bottom of the test tube. Also there was a sizzling\popping noise. Why did it change colour and why was there a noise? What caused this?


texts: How to prove it mathematically that either rhombic or the monoclinic sulfur is denser?

texts:
For the transition, rhombic sulfur → monoclinic sulfur, the value of $ΔS$ is positive. The transition temperature increases with increase in pressure. Which is denser, the rhombic or the monoclinic form? Prove your answer mathematically.

I tried by using Clapeyron equation but still failed. How should I approach and solve it? This is so tricky.


texts:
I have a question regarding the solubility of baking soda (bicarb soda) in oil. I am pretty sure that it has poor solubility, but I have a chemistry dilemma and cannot seem to solve it.

I make all-natural deodorant, and the main ingredients are coconut oil, shea butter and baking soda (amongst a few other ingredients). We have been making it for years, and it was always soft and smooth, but this time the baking soda is not dissolving and leaves a gritty texture (even after sifting baking soda to remove lumps).

Does anyone have any idea why this might be? We heat the ingredients to melting point on the stove, then let cool to room temperature and re-solidify in the fridge for a day, before using.

The only thing I can think of is that we have recently changed to a new brand of baking soda; however, with adequate mixing, surely that would not change the final texture so much.

Thank you!


texts: Understanding the use of Le Chatelier's principle in the industrial production of ammonia

texts:
I understand why the reaction

$$\ce{N2 + 3 H2 -> 2 NH3} \qquad \Delta H = \pu{-92.2 kJ mol-1}$$

isn't carried out in the lowest possible temperature (even though it seems that it should be as it favors the right side of the reaction). As the rate of reaction would be very slow, the amount of $\ce{NH3}$ produced would be lesser than the amount that would've been produced if the reaction was carried out at the optimum temperature in a given time span.

Why isn't then the reaction carried out at the highest possible temperature since the rate of reaction would be very high and the yield would be very high consequently as well?


texts: Formation of radicals from C-H and C-C bonds

texts:
Why do radical mechanisms favor the homolytic dissociation of a $\ce{C-H}$ bond over a $\ce{C-C}$ bond?

The $\ce{C-H}$ bond is stronger in magnitude (and it's also slightly polarized), so why would it break more easily as compared to the $\ce{C-C}$ bond?

My instructor explains this by claiming that the products of $\ce{C-H}$ bond dissociation are stabler than$\ce{C-C}$ bond dissociation.

I know that radicals are unstable and highly reactive, so why does it make any difference as to which radical is formed? Wouldn't the radical easiest to form be the one formed the most?


texts: What is the reaction mechanism for the hydrolysis of Amifostine?

texts:
I have to do research on a drug called Amifostine: 2-(3-aminopropylamino)ethylsulfanyl
phosphonic acid.

I'm supposed to say how the organic reaction works inside the body.  I understand that it's hydrolyzed by an enzyme into its active form; 2-((aminopropyl)amino)ethanethiol.

I don't get what happens to the phosphonic acid functional group. Does the water break apart the $\ce{S-P}$ bond because it is a weak bond? And what does the acid group become? $\ce{H3PO4}$?


texts:
This question is primarily related to stack testing data.

Whenever stack testing is being conducted and the parameter being measured is VOC concentration, it is often reported as ppm (as hexane) or ppm (as propane) and so on.  My question is: what exactly does it mean physically to say ppm as hexane vs. ppm as propane or heptane and so on?

My apologies if it's a stupid question.  I think my question probably gets into a little bit about how a flame ionization detector actually works.


texts:
The following is the answer for a question that I am doing:

  Reduction: $\ce{X^2+(aq) + 2 e- -> X(s)}$

Can I write $\ce{X + 2 e- -> X^2-}?$ Why can't I start with $\ce{X}$ instead of $\ce{X^2+}?$

EDIT:
The question:

Deduce the balanced equation for the voltaic cell constructed using metals B and C as electrodes.

Context:


texts:
There are only a few naturally occurring liquids I can think of on earth, such as water, mercury and animal oils.

Why are naturally occuring liquids more rare than solids and gasses on Earth?

To be specific,

By Earth I mean the surface which is inhabited by humans, not the interior core or mantle.
I am referring to naturally occurring substances, i.e. naturally occurring liquids are far more rare than naturally occurring gasses or solids. Why is this?
I am referring to average conditions of temperature and pressure that prevail on our planet's surface, not man-made conditions or extremities.

Current Line of Thought

I looked into inter-molecular forces for an answer. Here's what I've come up with.

At Earth's temperature, substances held by dipole-dipole forces are solid and substances held together by weaker london forces are liquids or gasses, such as oils or noble gasses.

The majority of substances have dipole-dipole interactions, hence are solids. In comparison, london forces are weaker so require only a little energy to change phase, which is why non-polar and noble-gasses are gasses or liquids at the same temperature. However, the majority of substances or not noble gasses or non-polar, which is why solids are more common on Earth.

To sum, dipole-dipole are the most common inter-molecular forces. Substances with dipole-dipole forces are solids at earth's temperature, hence the majority of substances are solids.

I am aware that many exceptions arise to this general trend, such as water, however the fact remains that liquids are more rare than solids and gasses on Earth.

I still have a feeling I am wrong, so if anyone could provide a better answer or critique on my line of thought that would be great.

Updated the question with specifics to make it less broad


texts: How to calculate the resonance energy of thiophene?

texts:
How to calculate the Resonance energy of Thiophene?
I know how to calculate the resonance energy of Benzene. I am applying same procedure for thiophene, too. (Wikipedia: Resonance energy)

The values are taken from NIST Chemistry WebBook.

\begin{array}{lccc} \hline
  \frac{\text{Heat Of Formations}}{\pu{kcal mol-1}} &
  \text{Thiophene} &
  \text{Tetrahydrothiophene} &
  \text{2,5-Dihydrothiophene}\\
\hline
\text{Experimental}          & 27.82 & -8.03 & 20.86 \\
\text{Using Argus Lab (AM1)} & 29.65 & -13.7 & 15.31 \\
\hline
\end{array}

From moving from tetrahydrothiophene to 2,5-dihydrothiophene, there is a change of $\pu{28.89 kcal/ mol}$, so ideally thiophene should have
$28.89 \times 2 (=57.78) \pu{kcal/mol}$ more energy of formation, but it has only $\pu{35.85 kcal/mol}$ more. This difference should be called resonance energy, i.e. $\pu{35.85 kcal/mol} - \pu{57.78 kcal/mol} = \pu{-21.93 kcal/mol}$.
In the literature, the value is given as $\pu{-29 kcal/mol}$. (1) (2)

I applied the same method on furan, where I got an error within 1%, but in case of thiophene, I am getting an error of about $\pu{7 kcal/mol}$.
Why? When using Argus lab the error even reaches above 50%.

I've posted this question on another forum also. I didn't get any satisfactory answer. Why in the cases of benzene and furan does this method work, but in case of thiophene I'm getting this error?


texts: How can Ellingham diagrams be linked to Gibbs energies of formation?

texts:
My textbook1 quotes the following as the limitation of Ellingham diagram:

  The interpretation of $\Delta G_\mathrm{f}^\circ$(standard Gibbs free energy of formation) is based on $K$ ($\Delta G_\mathrm{f}^\circ = -RT \ln K$).Thus it is presumed that the reactants and products are in equilibrium.

Definition of Standard Gibbs free energy of formation:

  The standard Gibbs free energy of formation of a compound is the change of Gibbs free energy that accompanies the formation of $\pu{1 mol}$ of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at $\pu{1 bar}$ of pressure and the specified temperature, usually $\pu{298.15 K}$ or $\pu{25 ^\circ C}$).

But in Ellingham diagram  reactants are normalized to consume one mole of oxygen having partial pressure of $\pu{1 atm}$. Thus products formed are not one mole. So how can it be a graph of Standard Gibbs free energy of formation and how this limitation even applies?

1. NCERT Chemistry Textbook for Class XII - Part I, Chapter 6, page 152


texts: Can hydrogen plasma reduce carbon dioxide?

texts:
There are several studies describing usage of hydrogen plasma to reduce metal oxides. This is not yet widely adopted in industry, but it is of interest for environmental reasons (such as desrcibed in Sabat et al. 2013).

I was wondering if the same could be done with carbon dioxide. If not, why not? Is there a way to calculate which oxides can be reduced this way?


texts: ortho/para-Selectivity in the Reimer-Tiemann Reaction

texts:
I can't figure out why the dichlorocarbene molecule produced in the Reimer-Tiemann reaction gets attached to the ortho position of phenol.
The ortho position is sterically slightly more hindered due to the oxygen, so why dosen't the carbene attach to the para position?


texts: Why are optically active compounds abundant in nature?

texts:
Enantiomers have most physical properties exactly same, which makes them hard to seperate from one another. Due to large amounts of physical similarities and chemical similarities (when dealing with optical non active compounds) anyone will assume that if I eat any one of enantiomers of some compound I will get same amount of energy and they will perform exact same task in my body.

Given that many optically active compounds are extracted from nature, why do organisms go through pain of separating enantiomers for their consumption? Why do optical isomers are found in nature that are hard to separate in a lab?


texts: Boundary lines in phase diagrams and the lever rule

texts:
My first question is: What exactly happens on a point situated on a line? Or on a point such as E in this figure?

Does point E mean that the $\delta , \gamma + \delta , \delta + \epsilon , \gamma + \epsilon $ phases all coexist here? If so, then why would it be considered a eutectoid invariant point where three phases coexist if in reality there are more than three phases coexisting?

My second question is: How can I apply the tie line and lever rules on a point on a point situated on top of a line, if I want to find Liquid percentage Solid Percentage, and maybe concentrations of one component in the liquid phase and solid phase? Is it undefined on top of the line?

Also, regarding the nature of the lever rule, is it some sort of empirical rule without any real theoretical foundation? At first glance, I can't believe it's actually accurate. Why is it true?

Thanks and sorry if my questions are unclear...


texts: What is the heat needed for an isothermal expansion of gas. Why do physics and chemistry yield different answers?

texts:
One mole of a certain ideal gas is contained under a weightless piston of a vertical cylinder at a temperature T. The face of the piston opens into the atmosphere. What is the heat supplied in the process to expand the gas from volume $V_1$ to $V_2$ isothermally ? Friction of the piston against the cylindrical wall is negligible is small

Now thermodynamics is a common topic to both physics and chemistry and as per my understanding of thermodynamics I am getting different results for the heat that will need to be supplied.

Chemistry says $$∆U =∆Q +∆W $$ and defines work as the work done on the gas and this will give $$W = -P_{atm}(V_2-V_1) $$ and as for isothermal process$$ ∆U =0 , ∆Q =P_{atm}(V_2-V_1)$$

According to physics on the other hand $$∆Q =∆U+∆W$$ and here the work done is the work done by the gas. That is

$$W = \int_{V_1}^{V_2} PdV=\int_{V_1}^{V_2} \frac{RT}{V}dV = RT \ln V_2-RT \ln V_1$$ and as for isothermal process $$∆U =0 ,\, ∆Q =RT \ln \left(\frac{V_2}{V_1}\right)$$

I am also uncertain that maybe neither of these is the correct expression and the network ok is actually in that work from both these forces and we have to take the sum of these to yield $$∆Q =RT\ln \left(\frac{V_2}{V_1}\right)-P_{atm}(V_2-V_1)$$

Now the value of Q should be unique because in the real world when we perform an experiment, only one value of Q would be supplied.

So which one of these is correct and where am I lacking in my understanding of thermodynamics from a chemistry  standpoint ??

Now as this question links both physics and chemistry, I want to post it on both sites (I hope it's fine) and the link to it is here


texts: About nitrogen acidity in function groups

texts:
I have a compound and it has several nitrogen atoms. I wish to know how do we differentiate between the basic and acidic nitrogens?

This is an example compound:


texts: I have just started inorganic chemistry in school and I have just learnt about metal aqua ions and how they react in water. I learnt that $\ce{[Fe(H2O)6]^2+}$ reacts in water by losing a $\ce{H+}$ acting as a Bronsted-Lowry acid producing $\ce{H+}$ ions. Due to this reaction we can test for metals such as $\ce{Fe^2+}$ by reacting it with $\ce{NaOH}$. This is because the $\ce{OH-}$ ions react with the $\ce{H+}$ ions produced pushing the equilibria to the right forming a insoluble precipitate. My questions is, why does the reaction stop there? The reaction stops once $\ce{[Fe(OH)2(H2O)4]}$ forms which is the insoluble precipitate but why doesn't it continue to form $\ce{[Fe(H2O)3(OH)3]-}$ and become soluble again?


texts: Confused about inversions in $S_N2$ Reaction

texts:
I just learned that in $S_N2$ reaction there is an inversion of configuration. I thought that it is a change of $R$ to $S$ and vice-versa. But that is wrong as mentioned in this answer.

While I was referring to more sources I saw this.

Here it is mentioned that $S$ to changes to $R$. Shouldn't that be wrong as absolute configurations do not change?

EDIT:
I solved a few problems and I think that $R$ to $S$ (and vice versa) inversion takes place when the attacking nucleophile is having the same priority (according to CIP rules) as the leaving group. Is my logic correct ?


texts: Reactivity order in hydrogenation reaction of but-2-yne and butene isomers

texts:
Question 1:

  The reactivity order towards hydrogenation of the following compounds is:

  but-2-yne ($\ce{CH3-C\bond{3}C-CH3}$)
  cis-but-2-ene ($\ce{CH3-CH=CH-CH3}$)
  trans-but-2-ene ($\ce{CH3-CH=CH-CH3}$)
  2,3-dimethyl-but-2-ene

Question 2:

  Which of the following has the lowest heat of hydrogenation per mole:

  cis-2-butene
  trans-2-butene
  1-butene
  1,3-butadiene

In the first question, I understand that 2 > 3 (cis is more reactive than trans generally)  and 4th is the least reactive (steric hindrance). But I am not quite sure about the order of (1). I could think that alkynes are more reactive toward hydrogenation because they have more pi electron density because of which its adsorption on the surface of metal catalysts will be easier. Is that the reason?
I have also read that alkynes are more reactive because they have less number of substituents around them. Which logic is correct and why?

I am more confused in the second question since there are just so many factors to compare - more no of pi bonds (more electron density) (according to my above logic, it should increase reactivity), steric hindrance, increased reactivity of cis isomers. I can make out that a > b (cis is more reactive than trans)  and d > c (more electron density) in terms of reactivity toward hydrogenation but how do we compare the others?


texts:
I'm asked the following:

  Explain why the structure $\ce{H-C=C-H}$ doesn't make sense chemically.

Not only am I just looking for a check up of my answer, but am I making any sense in what I'm saying here? Am I mixing up or misunderstanding concepts here?

My answer was:

The hydrogen and carbon atom form a covalent bond. Hydrogen has only 1 electron in its valence shell, so it 'needs' 1 of carbon's electrons to complete it. Now there are 3 electrons left to take in the carbon atom. But this isn't enough to make a double bond with the other carbon atom: we're one electron short.

Does this sound about right?


texts: Can you eliminate cigarette smoke odor between walls?

texts: If holes are made in dry walls is there a substance that can be sprayed in the walls to eliminate cigarette  odor?


texts: Electrodes involving sparingly soluble salts (Electrodes of the second kind)

texts:
Consider the sparingly soluble salt, $\ce{AgI}$ ($K_\text{sp} = 8.52\times10^{-17}$) and a silver electrode (Standard Reduction Potential = $\pu{0.799V}$). $\pu{0.02L}$ of $\pu{0.001M}~\ce{KI}$ solution is added to a silver nitrate solution with a silver electrode immersed. After connecting to SHE, the reading is $\ce{0.068V}$. Hence, what is the concentration of silver nitrate added at 298K?

Clearly, we should start off by writing the relevant Nernst equation, as follows
$$E = \pu{0.799V} - \frac{8.314 \times 298}{1 \times 96485}\ln\left(\frac{1}{[\ce{Ag+}]}\right) $$

From here we can substitute $E = \pu{0.068V}$ and obtain a result of $[\ce{Ag+}] = 4.331 \times 10^{-4}$

However, I am not sure how to proceed from here. An unknown amount of $\ce{AgI}$ precipitated and so we cannot calculate the initial amount of silver nitrate added. Although we know the amount of $\ce{KI}$ added, most of it presumably precipated due to low [$\ce{I-}$] from $K_\text{sp}$, suggesting excess silver nitrate. However, the still low concentration of silver nitrate presents problems when we use approximations.


texts: Influence of solubility on the complexation constants at different pH values

texts:
Given some small chemical compounds whose solubility varies with pH, and in the case of compounds that can form complexes, I have seen that the complexation constant varies with pH.

I think there might be two main reasons for this:

Chemical structure of the host system is affected by pH (for instance, protonation) and therefore it affects complexation constant;
It might be related to the small chemical compound, since its solubility might vary according to pH.

So I guess that in this case there are many chemical/physical equilibria involved, in this case mainly phase solubility and protonation for both species. I wonder what is the best approach for describing this, perhaps one can use different equilibrium constants for the mentioned equilibria, and from there derive a global constant that depends on pH. How do these two factors (protonation and phase/solvation) influence the value of the complexation constant?

As a particular case, I am mostly interested in complexation of flavonoids with cyclodextrins.


texts: Multiplet shape in proton NMR of morpholines

texts:
I recently carried out a Buchwald–Hartwig reaction to attach a morpholin-4-yl group to an aromatic ring:

In the proton NMR of the (columned) product, I found the peaks corresponding to the morpholine protons. The multiplet at 3.86 ppm comes from the protons next to oxygen, and the protons next to nitrogen give rise to the multiplet at 3.04 ppm:

The spectrum was obtained on a 400 MHz spectrometer and the values of the "coupling constants" are shown in the second multiplet. (They are identical in the first one.)

Why do the peaks have the fine structure that they do? Based on a simplistic analysis (the "n+1 rule"), I would expect a 1:2:1 triplet for both of these peaks.

In my crude NMR (pre-column) there was some excess morpholine and those peaks had exactly the same fine structure.

Does it have something to do with the chair conformation of the six-membered ring and the differentiation between axial and equatorial protons?


texts: What Does Electrical Work Represent in Context of Electrochemical Cells?

texts:
If cell operates reversibly than change in Gibbs energy of system equals electrical work of the cell. As far as I know electrical work is work done by electric field when charge moves between certain potential difference which in case of electrochemical cells is potential difference between two electrodes: $$ W = -zF\Delta E $$
Here work is written per mole of reactant consumed or product formed in electrochemical reaction. It is said when cell is short circuited that cell does no electrical work. How is this possible if charge moves through certain potential difference? What does the fact that there is no load connected to the cell A.K.A cell is short circuited have to do with electrical work since charge will still move between two electrodes or certain potential difference?


texts: Will bridged compounds the undergo SN1 reaction?

texts:
$\mathrm{S}_{\mathrm{N}}1$ reaction involves only one molecule in the rate determining step. So, the molecule which undergoes $\mathrm{S}_{\mathrm{N}}1$ reaction should be stable when it forms a positive ion. $\ce{(CH3)3C^+}$ is considered stable due to inductive effect from the three carbon atoms and also hyper-conjugation. But, what about bridged compounds like 1-bromobicyclo[2.2.1]heptane:

When $\ce{Br^-}$ is abstracted the positive ion formed will be stable and therefore this will undergo $\mathrm{S}_{\mathrm{N}}1$ reaction. Am I thinking right? Please help me correct myself.


texts: Dangers of using activated carbon past its lifespan

texts:
Activated carbon (AC) is one of the most widely used media for water filtration. It's effective at removing chlorine taste and odor, and it's recognized as being safe.

However, most activated carbon filters have an indicated lifespan of about 4-6 months, after which they need to be replaced. But is there any risk to using an AC filter past its lifespan other than the fact that it won't effectively filter contaminants anymore?

I've read in passing that an AC filter past its lifespan can actually release contaminants in water, because some contaminants in the influent water may be preferentially adsorbed by the AC, replacing existing contaminants previously trapped in the AC and causing them to be released in the effluent water. Is this something that has been explored in research?

In particular, has it been shown that using a saturated AC filter can cause the levels of certain contaminants — e.g. a trihalomethane such as bromoform, or perhaps fluoride or lead — to rise to a level that is well above the EPA maximum contaminant level?


texts:
Me and my classmates are doing an experiment in order to determine the pH of Sprite. We are going to conduct a titration with NaOH.

We are taking under consideration that the citric acid in Sprite is the only thing that is causing the drink to be acidic.

Our question is how do we calculate the pH of the drink.
We determined that it took 26,9 ml of NaOH to make the solution of sprite (50ml) and water (50ml) neutral (pH=7).


texts: What is the patina formed on copper pennies?

texts:
I'm currently taking high school chemistry and I don't quite understand my results from my experiment.

I had two pennies where both were put into a mixture of salt and vinegar. One of the pennies was dried and cleaned and the penny was like brand new. While the other penny Is left it in the mixture for 2 and 3 days with water.

Once I took it out, the penny had patina  forming. I'm not quite sure what type of reactions are occurring here and what elements/compounds are coming into play.


texts: Conditions for spontaneity of redox reaction among redox couples with equal standard reduction potentials

texts:
A question from the university course:

Could a redox reaction spontaneously occur among the redox couples $\ce{A_{ox}}/\ce{A_{red}}$ and $\ce{B_{ox}}/\ce{B_{red}}$ within non-standard circumstances if they have the exact same standard reduction potentials? So then, under which conditions?

The lecturer used the Nernst equation as follows for this question:
$$\Delta E = \Delta E^{\circ\prime} + \frac{RT}{zF} \ln{\frac{[\ce{A_{ox}}]}{[\ce{A_{red}}]}} - \frac{RT}{zF} \ln{\frac{[\ce{B_{ox}}]}{\ce{[B_{red}}]}}$$
From my understanding he is calculating the energy that is needed to run the reaction spontaneously, but I don't understand how he came to this equation.
If the reduction potentials of two half-reactions are the same, is it still possible for them to run spontaneously under certain conditions?


texts: Probability of forming dihydrogen with molecular weight 3

texts:
During a lecture, my professor told us that the probability $P$ to form a hydrogen molecule $\ce{H2}$ with mass number 3 could be calculated out of the abundances, $\gamma$, of the isotopes of this element: $\ce{^1H}$ (normal hydrogen), $\ce{^2H}$ (deuterium), etc. So,
$$
\begin{split}
P[\ce{H2}] &= P[(\ce{^1H} \cap \ce{^2H}) \cup (\ce{^2H} \cap \ce{^1H})] \\
%
           &= P[\ce{^1H} \cap \ce{^2H}] + P[\ce{^2H} \cap \ce{^1H}] -
%
              P[(\ce{^1H} \cap \ce{^2H}) \cap (\ce{^2H} \cap \ce{^1H})]
\end{split}
\tag{1}$$
But since
$$(\ce{^1H} \cap \ce{^2H}) \cap\ (\ce{^2H} \cap \ce{^1H}) = \ce{^1H} \cap \ce{^2H}\tag{2}$$
and
$$P[\ce{^1H} \cap \ce{^2H}] + P[\ce{^2H} \cap \ce{^1H}] = 2P[\ce{^1H} \cap \ce{^2H}]\tag{3}$$
we end up with
$$
\begin{split}
P[\ce{H2}] &= P[\ce{^1H} \cap \ce{^2H}] \\
       &= \gamma(\ce{^1H}) \cdot \gamma(\ce{^2H}) \\
       &= 0.99972\cdot 0.00028 \\
       &= 0.0002799
\end{split}
\tag{4}$$
This is my result while for my professor, it should be twice that value. It's like he's forgetting the term
$$
P[(\ce{^1H} \cap \ce{^2H})\ \cap\ (\ce{^2H} \cap \ce{^1H})]
$$
Am I right?


texts:
I have seen some heating apparatus for a crucible use a retort stand with a large metal ring attached to the boss head to support the clay triangle as shown below.

Instinctively, I would have placed the clay triangle on a tripod, however, I see that this has certain advantages, such as being able to adjust the height of the crucible so that it is in the hottest part of the flame.

My question is: What is the name of this piece of laboratory equipment, I have seen it sometimes referred to as an iron ring, but is there a more formal name?


texts: Why are some annulenes such as [14] and [18]annulenes are aromatic even though they are not fully planar as cited by Wikipedia? What does it mean that they can achieve planar form?


texts: What are the essential arrows for entering chemical equations in text?

texts:
I'm the author of a custom chemistry keyboard on iOS. I am looking at improving the selection of Unicode arrows I can provide. When the device is a phone in portrait mode, I don't have a lot of extra room on screen, so I give a flyout with:
→, ⇌, ↔, ⇢, ↛
When the phone is rotated or it's on a larger device, I have some extra room, so I was thinking about adding either more items in that flyout, or perhaps another button with an expanded set. Maybe something like:
⇄, ←, ↝, ↮⟿
I would like to make the most useful unicode arrows available, and not provide ones that nobody would use. I expect that this will vary from speciality to speciality, but I'd really appreciate some feedback.
I'm limited to what is in Unicode. (If you are on a Mac, you can bring up the Emoji and Symbols palette and look at the Arrows category)


texts: Stability of methoxy-methyl and tropylium carbocations

texts:
Which is expected to be more stable: methoxy-methyl carbocation
$(\ce{CH3-O-CH2+})$ or tropylium $(\ce{C7H7+})$ cation?

I think because oxygen would donate its lone pair so there will be complete octet formed that would make it more stable. Is this argument true and can it be applied everywhere against resonance?

Is it wrong to say tropylium cation is exceptionally stable?

What would be its (tropylium cation) comparison against cyclopropyl cation?


texts: Elimination reactions of vicinal dibromide

texts: When a vicinal dibromide undergoes elimination reactions in vigorous basic conditions, say in ammonia with $\ce {NaNH2}$, is the product an alkyne or is it a conjugated diene? I would think that the answer depends on thermodynamic and kinetic factors. Considering bond energies of the $\ce {C-C}$ $\pi$ bonds, perhaps the conjugated diene would be more favourably formed?


texts: Quadrupole MS: mass as a function of voltage

texts:
Every time I see an article about Quadrupole MS (e.g. here), they give formulas like:

$$ a_x = \frac {8eU} {m r_0^2 \Omega^2} $$ and $$q_x = - \frac {4eV} {m r_0^2 \Omega^2}$$

I suppose the instrument changes voltage and keeps the rest constant, but I failed to find any article that would show direct formulas on how to calculate m/z from that. I could rearrange it like this:

$$ \frac {m} {e} = \frac {8U} {m r_0^2 \Omega^2 a_x} $$ But this doesn't really help because $a_x$ itself is unknown and is derived from mass.

PS: this question is about Quadrupole MS though it looks to me that Ion Trap MS has very similar concepts and math.


texts: Nomenclature of Coordination compounds containing nitrogen

texts: As Per rules , amine when present as a ligand is written as "ammine" with double m's , so a compound having a complex ligand such as ethane-1,2-diamine , will be written with 1 'm' amine or double 'm' ammine?


texts:
Somehow I am told that my product is incorrect. Why is my product incorrect?

As far as I can see this is a Wittig reaction resulting in a two carbon increase with removal of the oxygen.

The only thing that strikes me as odd is that the Wittig is conjugated to a bromide salt. The only way this can happen is if the phosphorous part has an overall positive formal charge. Does this mean that the n-butyllithium will abstract a proton and leave the carbon backbone of the Wittig as $\ce{CH3CH}$?

Even so this doesn't seem to affect my final product ...


texts: What is parachemistry? What does a parachemist do?

texts:
I was reading the Washington Post article An atomic town revels in its nuclear past as tunnel collapse raises contamination concerns and came across a quote from someone who was said to have been a "parachemist" at the Hanford nuclear facility in the US state of Washington.

Is parachemistry a recognized subfield of chemistry? If not, what else could this mean?


texts:
H2O has two lone pair electron and H2S also have two lone pair electron but Bond Angle in H2O is 104.5° but H2S has 92.12°bond Angle .

Both H2O and H2S has same hybridization ,which is sp3 and i know that the four hybrid orbitals of sp3 hybridization are directed towards the four corner of a regular tetrahedron making Angle of 109.5° .

My teacher taught me that for every lone pair you have to subtract 2.5° from 109.5° so if that's the case then both of them should have same Angle as both of them have 2 lone pair electron ?
If that's not the case then what is the exact way to determine Bond Angle ? And the way my teacher taught me is it ok ?


texts: Is there a quantitative test/analysis technique that can determine if some chloroform has degraded into phosgene?

texts:
Before I go to use any chemical that I've had in storage for a while, I try to check if it's degraded into something else (e.g.: checking the $\ce{H2O}$ content of $\ce{H2O2}$, checking for $\ce{H2O2}$ in $\ce{Et2O}$, etc.). This can usually be done using the appropriate test strip.

I have a 3/4 full bottle of chloroform that's been sitting on a shelf for about a year (probably less, actually), in an amber bottle to restrict the amount of light that can get to the chloroform. I'm aware that chloroform can break down into phosgene, and I know there are some ways to test for this, but I was hoping for a quick quantitative test that can be done without any hassle, but I can't seem to find anything out there. The Wikipedia page for chloroform states:

  Suspected samples can be tested for phosgene using filter paper (treated with 5% diphenylamine, 5% dimethylaminobenzaldehyde in ethanol, and then dried), which turns yellow in phosgene vapor.

I don't have either of the diphenylamine or the dimethylaminobenzaldehyde, and would prefer not to have to purchase them just for this simple test (I don't have any use for either chemical currently).
Does anyone know if there is a simple quantitative test that accomplishes the same thing? Preferably a test strip.


texts: A polymer is sometimes defined as a macromolecule with MW larger than 1000 g/mol. So can graphene be considered a polymer?


texts: How accurate would be the following conclusion on 'Critical Temperature'?

texts:
"Boiling does not occur when liquid is heated in a closed vessel. On heating continuously vapour pressure increases. At first a boundary is visible between the liquid and vapour phases because liquid is more denser than vapour. As temperature increases more and more molecules go to vapour phase and density of vapours rises. At the same time liquid becomes less dense. It expands because molecules move apart. When the density of liquid and vapours becomes the same; the clear boundary between the two phases disappears. This temperature is called critical temperature"

That is EXACTLY what my textbook says. And that is where I am having doubts. It's because - a gas might still be found in its gaseous phase below the critical temperature if the pressure is considerably below its critical pressure ($P_c$) and it has a volume sufficiently larger than its critical volume ($V_c$).

Just consider any point in the Pressure-Volume isotherms of $\ce{CO2}$ given above, which is in the region of gas-liquid equilibrium (within the shaded dome shaped curve) but has a volume greater than the critical one. For e.g a point that lies

Within the shaded region.  and
On a line passing through B and parallel to the pressure axis.

Let that point represent the state of liquid inside the vessel.
From there if we increase the temperature, we would arrive at a point on the boundary of the dome shaped curve, (viz. B) but that point would be on a lower isotherm than the critical isotherm. And it looks like B is also a point where the two densities becomes equal.(isn't it?)
Based on that premise, we can't say that the temperature arrived at in the above (heating liquid in a clossed vessel) situation would necessarily be the Critical temperature.

What I want to ask is if my reasoning is correct or am I missing anything?

My question can be rephrased in the following manner also
Is it true that critical temperature is the only temperature at which the density of the gaseous phase of a gas becomes equal to its liquid density?


texts: I was looking up fluorine isotopes out of curiosity. The Wikipedia entry gives info on them but adds there are also two isomers which are $\mathrm{^{18m}F}$ and $\mathrm{^{26m}F}$. What is an isomer of an atomic nucleus please someone?


texts: What is the common denominator of all the lipids?

texts:
I've read the lipids article on Wikipedia, but I couldn't understand the answer for my question and I'll explain why.

In biochemistry we have monomers and polymers while the monomer is the basic unit molecule for the polymere. In protein for example, we have amino acid that this is the basic unit of the proteins. Amino acid is characterized as structure of 4 groups: Alpha carbon, amine group, carboxylic group, hydrogen and R chain. this is the basic of all the amino acids.

But when we are talking about lipid as a main family of molecules (like what we have we have with protein) then I can not understand what is the "amino acids" (parallel) of them, i.e. what is the basic unit of the lipids and what is the structure.

Well, I could understand that the fatty acids are the analogous for the amino acids, but the problem is that fatty acids according the article (and other schemes that I saw on google pictures), they are considered as subgroup of the lipids, and that says that not all of the lipids are made of them. So I don't have clue for the answer to my question.


texts: Is it possible to separate/remove sugar from common drinks, such as juice?

texts: Is it possible to remove sugar from a drink (for example, juice) using common household equipment?


texts:
I was reading the topic alcohol in that I saw a reaction Pinacol pinacolone rearrangement .

But I am not able to find the sterochemistry of the reaction .

Can anyone please tell me the stereochemistry


texts: It seems that all wave functions studied in physical chemistry are orthogonal (e.g. particle in a box, hydrogen atomic orbitals). Does this come about because we purposefully make them orthogonal, or are they derived that way naturally? Can there be useful wave functions that are not orthogonal?


texts: In what way could benzoin give Tollen's test?

texts:
In Q29 of Joint Entrance Exam (JEE) 2016 India, the official answer key mentions that benzoin gives Tollen's test. However, I saw this post which says that it doesn't: Why do α-hydroxy ketones give Tollens' test?

Benzoin:

I'm very confused now. If benzoin does give the test, how? And what is the mechanism/intermediate involved?

I thought of all possible reactions benzoin may undergo in basic medium:

I did its aldol condensation but the product was too crowded and seemed quite unlikely. It didn't have any aldehyde group.
Another possibility seemed oxidation to benzil, but I'm not sure. I don't think $\ce{Ag+}$ is strong enough.
I was thinking about cleavage of central $\ce{C-C}$ single bond — as the hydroxyl $\ce{O}$ donated its lone pair to the carbon it is attached to, but am not sure on this too.

I couldn't find any related reaction of benzoin or any rearrangement on the internet.


texts: Why does this elimination reaction occur?

texts: I was confused by why the following elimination reaction hits only one of the hydrogens instead of both isomers that are possible. Please help me out!


texts: Contactless non-ferrous metals hardening?

texts:
Is it possible to work-harden non-ferrous metals without direct contact?
I know induction hardening is used on ferrous metals, but would like to know if a technique exists for non-ferrous metals.


texts: When, if ever, can standard enthalphy be subsituted for standard chemical potiential?

texts:
I'm reading through a combustion modeling paper by Gordon & McBride which is a bit scant on some of the algebra & calculus used to derive their equations. My advisor and I have derived nearly all the equations missing clear derivations except for a few where the chemical potential seems to be have been completely substituted for by standard enthalpy.
We are mathematicians, and we figure this is likely some clever algebraic trick using a chemical equivalence we are unaware of, but which is so well-known to a chemistry audience that the authors did not bother to include the pertinent equation. The only thing I can think of is that somehow the Gibbs definition was used. However, there is no entropy in the final equation, as I would expect if the Gibbs definition were used to substitute for chemical potential.
Do you chemistry folk have any pointers for a lost math fellow?


texts: Lab test to compare the reactivity of liquid 1-heptene and liquid heptane

texts:
Describe how you would carry out a lab test to compare the reactivity of liquid 1-heptene and liquid heptane. State clearly what the possible results of the test are and what they would indicate.

Would you carry out the lab test using bromine?
Add about 1 mL (about twenty drops) of 1-heptene to one
container and about 1 mL of heptane to the other container.
Add an equal volume of bromine water to each of the liquids then
shake each container to the same extent.
Leave the containers to settle, then observe.

Would this process work for heptane and 1-heptene? Would the colour of the solution change?


texts: What causes soda to fizz and how can it be stopped?

texts:
When you go to a soda fountain and pour some soda into your cup, frothy fizz is generated at the top of the cup. Obviously, it has something to do with carbonation. However, when a cup of soda is just sitting and is not being filled or refilled, there is no fizz.

What causes the fizz? Is the fizz generated by the crashing of the soda into the cup?

I would also like to know how to stop the fizzing produced when the soda cup is being filled/refilled: Can I slow the rate at which the soda falls? Will spinning the liquid on the way down to the cup help attenuate the fizzing? What about changing the material from which the cup is made?


texts: Experience with PTFE tubing & glass connectors?

texts:
I'm wondering which PTFE tubing size to get to connect to normal 10mm OD glass connectors. For a silicon hose I would take an ID of 8-9mm as it is flexible but I think PTFE is quite rigid.
Anyone has some experience with PTFE tubing?


texts: Why don't 1,2-substitued alkenes polymerize as much as mono or disubsituted alkenes?

texts: Ethylene, propylene, PVC, acrylates. All of these monomers that are industrially produced seem to only have substituents on one of the carbons, rather than both. Why don't we usually see 1,2-substituted alkenes undergoing polymerization? Sterics? Electron cloud interference?


texts: UV radiation on IBr (Radical Substitution)

texts: I came across a radical substitution which Methane reacts with $\ce{IBr}$ to form iodomethane and hydrogen bromide and many more products. I understand the whole process but I don't quite see how the $\ce{IBr}$ molecule will break via homolytic fission instead of heterolytic. Since Bromine is more electronegative than Iodine, wouldn't $\ce{Br}$ takes both electrons and form $\ce{Br-}$ ions?


texts: I need to cool a tube containing liquid to −35 °C for a cold chemical experiment that will last about a week. The glass vessel I need cooled is 500 mL in volume and will be giving off $\ce{H2S}$ gas. I currently only have a fume hood. Most freezers do not seem capable of this low temperature. Most cryochemistry refrigeration seems designed for much lower temperatures, and is needlessly expensive. I realize that refrigeration is relatively simple: 1 compressor, 1 expansion valve, two heat exchangers, and electronic control/monitoring. My first impulse is to modify a freezer, but I am completely new to this. At this point I would be very happy with some general advice and perhaps a reference for custom designing these sorts of cooling devices.


texts: Generating molecular graph Laplacian based on Hückel theory

texts:
While studying graphs and graph Laplacians from "Laplacian eigenvectors of graphs: Perron-Frobenius and Faber-Krahn type theorems.", I encountered a type of graph Laplacians that rise from quantum chemistry. This matrix is consists of off-diagonal elements called resonance integrals and diagonal terms called Coulomb integrals. This is a sparse matrix, meaning that the matrix elements corresponding to non-connected atoms are zero. It is further mentioned that

  ... the entries of this matrix, H, are tabulated for different atoms and
  bonds.

I was looking online to find some table that gives this information and write a package to compute this matrix given a SMILES entry. As an alternative, I also looked for an already existing package that provides this matrix. The only thing I found was the implementation of the extended Hückel method in RDKit, which requires molecule conformation as input (apparently, eHM needs atom coordinates).

I was wondering if anyone can point me to such a table or python package or let me know if I'm missing something.


texts:
While documenting myself on the detectors used in HPLC, I came across one that I did not know: ELSD.
I understood that the sample with the mobile phase was nebulized at the column outlet but I do not understand what is measured next.
Could you clarify this for me?


texts: Atomic number ranges in "integral units"?

texts:
My textbook says the following:

  For an electrically neutral or complete atom, the atomic number also equals the number of electrons. This atomic number ranges in integral units from 1 for hydrogen to 92 for uranium, the highest of the naturally occurring elements.

I'm wondering what is meant by "integral units" in this context?

I would greatly appreciate it if people could please clarify this.


texts: Is it possible to isolate potassium triiodide from KI solution? Sources claim that this is possible because potassium is a sufficiently large cation and triiodide is a sufficiently large anion, therefore it is capable of forming a stable solid. This is an explanation based on HSAB, where triiodide is the soft base and potassium cation is the soft acid. Has anyone tried to do so?


texts:
I'm really unsure what the difference is. We're using these when calculating $K$ of combined reactions. In general, I am also confused what $K$ is in comparison to $K_\mathrm{a}$ and $K_\mathrm{b}$. For example here is a calculation where for the reaction involving $\ce{NO2-}$, the equilibrium constant is $1/K_\mathrm{a}$ even though it shows $\ce{NO2-}$ acting as a base.

  Use the following four aqueous species to write an acid-base reaction with $K > 1$. (An acid-base reaction is one that involves the exchange of a proton. Your reaction will involve all four species.)

  $\ce{NO2-(aq)}$, $\ce{F-(aq)}$, $\ce{HF(aq)}$, $\ce{HNO2(aq)}$

  $\ce{HNO2}$ $(K_\mathrm{a} = \pu{4.6e-4})$ is a weaker acid than $\ce{HF}$ $(K_\mathrm{a} = \pu{6.6e-4})$, so $\ce{HNO2}$ holds onto its proton more tightly than
  $\ce{HF}$. So if we write a reaction when $\ce{NO2-}$ takes a proton from $\ce{F-}$, we'll have a reaction with $K > 1$:

  $$\ce{HF + NO2- → HNO2 + F-}$$

  We can get the $K$ for this reaction that adding the two acid dissocation reactions together as:

  $$
\begin{align}
\ce{HF &→ H+ + F-} &\quad &K_\mathrm{a}(\ce{HF})\\
\ce{H+ + NO2- &→ HNO2} &\quad &1/K_\mathrm{a}(\ce{HNO2})\\
\hline
\ce{HF + NO2- &→ HNO2 + F-} &\quad &\frac{K_\mathrm{a}(\ce{HF})}{K_\mathrm{a}(\ce{HNO2})} = \frac{\pu{6.6e-4}}{\pu{4.6e-4}} = 1.4 > 1
\end{align}
$$


texts: Why can singlet oxygen participate in cycloaddition reactions while triplet oxygen, on the other hand, can't?


texts:
Phenols are hygroscopic and form a red liquid, upon contact with air. Yet, Phenol’s solubility in water is said to be moderate. ( Tilted to the low solubility side) This is explained with the benzene ring being non polar.
Then how can it be hygroscopic? Are solubility and hygroscopicity even related at all, then?


texts:
Wikipedia says that Ka was a symbol for potassium once.

  Current symbol is K.

  Name changed due to a standardization of, modernization of, or update to older formerly-used symbol.

When was the symbol for potassium changed from Ka to K? What was the rationale behind that?


texts: What are the predominant acids in sphagnum peat moss?

texts:
I'm trying to figure out what the predominant acidic substances in peat moss are. Peat moss is said to have a pH of approximately 4.0. So, I'm curious what is making it acidic.

I know not all acids bind to various elements in the same ways. So, I'm trying to find out which acids (and/or acidic salts) are present in peat moss in order to aid me in my research to discover approximately how long it might take to acidify soils with it compared with the traditional methods of adding various forms of sulfur to soil. You don't need to tell me how long it takes, by any means. I can do more research after I find out which acids or acidic salts are in peat moss, in what levels.

I'm not familiar with this particular SE site's customs. So, if this is the wrong place to ask, or if I used the wrong tag(s), feel free to let me know. I figured people might be more likely to know here than on Gardening and Landscaping, though.


texts:
We all know the very famous esterification reaction, where a carboxylic acid and an alcohol react to give an ester and water. But why do they actually smell? What is the reason behind its aromatic character?

I initially thought that it must be due to the conjugation between the two oxygens present. I do know that aromaticity is decided by the conjugated lone pairs present in the compound where the compound must follow Hückels rule. But it's only valid for a cyclic and a planar compound.

Why do esters have that fruity smell? What is the chemical explanation for a smelly non planar compound?


texts:
For oxalic acid, $\mathrm{K}_{\rm a1}> \mathrm{K}_{\rm a2}$.

My teacher told me that after first deprotonation, $\ce{COO-}$ acts  as an electron donating group and hence reduces the acidic strength of $\ce{HC2O4-}$ (due to the +I effect of $\ce{COO-}$ on the second $\ce{COOH}$).

Why is $\ce{COO-}$ an electron donating group when $\ce{COOH}$ is an electron withdrawing group?


texts: Mercury is a very good solvent for many metals. We have mercury metal available, how do we check for its purity? Is there some kind of test available to verify its purity? And, more helpfully, which kind of metals are dissolved in it?


texts: Does the Boltzmann distribution hold for supercritical fluids?

texts: Above the critical temperature of a real gas, if we compress it, to whatever extent, it doesn't get liquefied (no gas liquid interface). However, it does behave like liquids , esp. in case of very high pressures (upto 300 atm) it's physical properties are almost like liquids due to decreased intermolecular distance and increased intermolecular forces, yet is not a liquid but condensed vapors. Now , the Boltzmann distribution assumes negligible intermolecular forces so that the total energy of the system consists of only individual kinetic energies of the molecules, $E_{\text {total}} = \Sigma_i K_i$. So, in the aforementioned case of supercritical fluids, does the Boltzmann distribution still hold true, with only an increased number of energy states , including the intermolecular potential energies, i.e. $E_{\text {total}} = \Sigma_i K_i +\Sigma_{i≠j} V_{ij}$? Or will we have to search for another statistical distribution? Any help/suggestions please.


texts: Need to specify cyclic alkenes as cis or trans

texts:
I'm studying organic chemistry from John McMurry's book. Double bond's substituents can be on cis or trans configuration. An example for cyclic molecules is trans-cyclooctene and cis-cyclooctene, where the cis compound is more stable. On the other hand, in a naming exercise this molecule is named simple as -cyclohexene. None of the other molecules  in the same exercise was named as cis or trans.

So, my question is: In small rings is not necessary to specify cis or trans orientation because the trans orientation is less stable (maybe impossible to obtain)?


texts:
I'm in chemistry and I still have a hard time comprehending how to balance a chemical equation.
What are the main steps and general things to know?
thank you.


texts: Why does the passivation layer in DRIE protect just the mask and not the substrate?

texts:
Here's a good link as an introduction to DRIE:
BSAC: DRIE Process Development

The $\ce{C4F8}$ (refer Pg. 9 on the link) passivates the entire top layer. But when $\ce{SF6}$ ion bombardment occurs, only the region not covered by the mask is etched. Why does the passivation layer protect just the mask and not the substrate?

Additional reference: Surface Micromachining Techniques and Materials.


texts: The most convenient process to purify Oxalic Acid up to a high level of purity

texts:
I am set out to purify a batch of commercial oxalic acid with the aim in mind to end up with a highly pure product (starting from $\pu{4,000 ppm}$ total impurities and doing so with basic lab equipment and no advanced analytical capacity).
Looking at the distribution of solubility vs. temperature in aqueous medium (which - despite the widely discrepancy in data from different sources - seems to generally adopt a somewhat exponential shape), I was thinking that the best may be to carry out dissolution/filtration at high temperature, followed by fractional recrystallization.
A few questions remain though:

I have no idea how I could discriminate against Vanadium impurities with the basic equipment I have at my disposal.
According to the data I've found $\ce{V2O5}$ has a fairly low solubility at ~$\pu{10^{-1} g}/\pu{100ml}$ at $\pu{25 ^\circ C}$, a level which makes it much too soluble for proper filtration, and too little for the recystalization to efficiently remove it.
I found data for the solubility of Vanadyl Oxalate to be of ~$\pu{22 g}/\pu{100ml}$ at $\pu{20 ^\circ C}$, and that of vanadium oxalate complexes of ~$\pu{14.5 g}/\pu{100ml}$ at $\pu{25 ^\circ C}$, which makes it very close to the solubility of oxalic acid itself (though, unlike for oxalic acid, I don't have data for how the solubility of Vanadium evolves with temperature).
I had the notion that slowly recrystalizing the oxalic acid would yield better results, but I found an old paper* on its purification which found/states exactly the opposite, for a reason I don't very well understand. If someone had enough understanding to explain to me why a faster recrystalization would yield better results and/or to confirm/refute the paper's statement on the subject, I would greatly appreciate.
I read upon a preliminary search here on Chemistry Stack Exchange that upon excessive heating, oxalic acid decomposes into $\ce{CO2 + CO + H2O}$ (in the ~$\pu{103-185 ^\circ C}$ range), thus I was wondering if it would be worth it to attempt to further exploit the exponential shape of its water solubility vs temperature by carrying out the dissolution/filtration in a $\ce{CO2}$ atmosphere, maybe under a slightly increased pressure. Would that significantly decrease the rate of its decomposition or simply complicate things without significant advantage?

https://core.ac.uk/download/pdf/29156537.pdf


texts:
I'm asked to find $\Delta G$ for the isothermal compression of $\ce{N2(g)}$ (real gas) at $0\ \mathrm{^\circ C}$ if the gas expands from $P=1\space\mathrm{atm}$ to $P=1000 \space\mathrm{atm}$. The fugacity coefficients are $\phi=0.9996$ and $\phi=1.84150$ respectively.

I'm confused about two things:

My professor makes a distinction between $\phi^*$ and $\phi$, the first one being the fugacity coefficient for a pure gas and the second for a gas in a mixture. Are they the same in this case or did he make a mistake since there's not a mixture to begin with? (Not sure how Lewis—Randall rule can relate here since, again, there's no mixture to apply the relation between the two coefficients.)
I already calculated the Gibbs free energy if the gas were an ideal one, I got $\Delta G=15.688\ \mathrm{kJ\over mol}$. Since $G^E=RT\ln(\gamma)$, and I have the Gibbs energy for an ideal gas, I could find the Gibbs energy for the real gas when I get a value for $G^E$; but again, in order to find $\gamma$ I need both coefficients, the one for a mixture and the one for a pure gas.

Can anyone please let me know what am I doing wrong? Or if my approach is far from the right path? Thanks in advance.

EDIT:

I assumed that the data that was given corresponded to the values of fugacity coefficients for the pure gas, making it all simpler since $G^E=RT\ln(\phi)$, so I got $G^E_{N_2}=17.075765\ \mathrm{kJ\over mol}$ and then $\Delta G^R=1.387765\ \mathrm{kJ\over mol}$

What I don't understand is that according to those two definitions of $G^E$, I get that $\gamma=\phi$, which I know it's not right, how's it possible?


texts:
An example of a solution not in equilibrium
  (A) Chemical ph
  indicator
  (B) Acid/base buffer
  (C) Anhydrous solution
  (D)
  hypotonic solution
  (E) Supersaturated solution

I  eliminated A and B. Then, I chose E, which is a right answer. Nonetheless, I read then that theoretically any solution or system can be in equilibrium. So, why is the answer E but not C or D?


texts: Chemical Reagent Test sensitive at low concentrations

texts:
Would there be a spot test/tests that can detect either/both of the following molecules at low concentrations?

The likely concentrations are in the $10{-}\pu{50 mg/L}$ range in an aqueous solution. Ideally, I'd want something that does not need an exotic/expensive instrument.  e.g. a color change or precipitation or conductivity/pH change.

The background interference: The sample is Terrific Broth which has the following composition:

$\pu{12 g}$ Bacto tryptone
$\pu{24 g}$ Bacto yeast extract
$\pu{4 mL}$ Glycerol
$\pu{100 mL}\ \pu{0.17M}\ \ce{KH2PO4}$ and $\pu{0.72M}\ \ce{K2HPO4}$, sterile, to be prepared separately from the tryptone, yeast extract, and glycerol solution.


texts:
I have the following reversible bimolecular reactions

$$\begin{align}
\ce{A_0 +B &<=>[$3k_+$][$k_-$] A_1} \\[5pt]
\ce{A_1 +B &<=>[$2k_+$][$2k_-$] A_2} \\
\ce{A_2 +B &<=>[$k_+$][$3k_-$] A_3} \\
\end{align}$$

that can be written as follows

$$\begin{align}
\ce{A_0 +3B &<=>[$k_1$][$k_2$] A_3} \\[5pt]
\end{align}$$

The initial conditions are $[\ce{A_1}]_0 = [\ce{A_2}]_0 = [\ce{A_3}]_0 = 0$. I know rate constants $k_+$ and $k_-$ and would like to write rate constants $k_1$ and $k_2$ in terms of $k_+$ and $k_-$.

It would be great if you have any ideas. I am quite new to the topic. So far, I can only think of using some fitting algorithms to find $k_1$ and $k_2$.
Thanks!


texts: Distribution of reaction times in (typical organic) chemistry

texts:
Is there any research on how reported reaction times are distributed (in typical organic chemistry)?

I feel like I remember that there was a paper/talk discussing this, finding that there was a steep drop around 10-14 h (since one would then have to setup the reaction very late or come in very early for workup - to avoid staying in the lab in the midst of the night), but right now I cannot find anything on the topic.


texts: Could you charge a recharable battery with a voltaic cell?

texts: In class we were learning about voltaic cells and my chemistry teacher joked that after modern society falls, we'll be the only ones who can recharge batteries with simple voltaic cells. And this got me thinking, is this possible? Could I create a salt bridge cell, attach wires to a store bought rechargeable battery, and charge it? I'm really curious and I can't ask my chem teacher as he's in the hospital recovering from an emergency appendix removal


texts: Distinguishing between potassium chloride and sodium chloride

texts: I have these very large blocks of salt intended for a water softener in my house, but I'm not sure if they're potassium chloride or sodium chloride, according to what I've read they're both widely used for water softeners. I've thought about distinguishing them by weight but I don't have any sodium chloride with the same granularity as the salt blocks.


texts: If dG is a state function, why do reversible and irreversible paths differ?

texts: For a reversible process at constant T,P in a closed system with no non-expansion work dG = 0. For an irreversible process under the same conditions, dG < 0. Since dG is a state function I would expect two process at the same T,P to give the same result just as dS is calculated for reversible processes but can be applied to any process with the same initial and final states. I suspect that I have incorrectly assumed that the states for dG are the same but I'm unsure.


texts: Friend threw mercury in a fire, is this dangerous?

texts: My friend broke a mercury thermometer and threw the mercury in the fire. Is this dangerous? and what should she do about the fireplace?


texts:
The relative reactivities of acyl compounds towards nucleophilic substitution is acyl chloride> anhydride>ester>amide.
I would like to know how  this kinetic property is decided. Is it on the basis of better leaving grp or is there another explanation for it?,


texts: What causes positive and negative deviations when weighing analytical samples?

texts: Positive deviations are when the measured mass is more than the true mass of the sample and negative deviations are when the measured mass is less than the true mass of the sample. What steps causes this type of errors in analytical measurements?


texts: What would happen to a diamond in the presence of oxygen and elevated temperature and how fast?

texts:
Let's say I have a $\pu{1cm^3}$  diamond and I put it into an oven where the temperature is about $\pu{ 400°C}$. We all know that diamond oxidizes. Would it evaporate or turn into graphite? If so, what would be the rate of reaction? Is there some way to calculate it?
From Wikipedia:

Above $\pu{1700^\circ C}$ ($\pu{1973 K}$/$\pu{3583^\circ F}$) in vacuum or oxygen-free atmosphere, diamond converts into graphite; in air, transformation starts at $\pu{\approx 700^\circ C}$. Diamond's ignition point is $\pu{720–800^\circ C}$ in oxygen and $\pu{850–1000 ^\circ C}$ in air.
[....]
But diamonds (sp3 carbon) are unstable against high temperature (above about $\pu{400 ^\circ C}$ ($\pu{752 ^\circ F}$)) under atmospheric pressure. The structure gradually changes into sp2 carbon above this temperature. Thus, diamonds should be reduced under this temperature.

So even if the diamond doesn't reach the temperature of $\pu{700^\circ C}$  it still oxidizes. That's why I'm asking.


texts: Claisen-like condensation with acid chloride

texts:
In the Claisen condensation, an ester enolate attacks an ester, with an alkoxide anion leaving subsequently to give a $\beta$-keto ester. Is it possible for a typical enolate of an aldehyde or ketone to react with an acid chloride (acting as the electrophile) to give a $\beta$-keto aldehyde or ketone, with the chloride ion leaving in a similar manner to how the alkoxide leaves in Claisen condensation?

Similarly, could I also extend it to the anhydride as well? Would we observe a similar Claisen-like mechanism?


texts: Generating Precipitation Diagrams with CompuTherm Pandat

texts:
I am trying to develop precipitation diagrams for an Ag-Cu-Sn alloy to figure out the kinetics involved using the CompuTherm Pandat Software (Demo Version).

The precipitation diagrams need the thermodynamics/mobility database and it further needs the kinetics database as well. The software I have installed comes only with Al-Ni Kinetic database.

Does anyone know how to get Pandat to generate diagrams for other alloys?
Their website is http://www.computherm.com/


texts: Why do ketenes participate in [2+2] cycloadditions with their $\ce{C=C}$ bond and not the $\ce{C=O}$ bond? Can the reactivity be reversed somehow?


texts: Why is ordinary soap and water adequate to decontaminate possible nerve agents?

texts:
In the news it was announced that anyone who might have been exposed in the recent Salisbury nerve agent incident should wash any potentially contaminated clothing as normal using regular detergent and water; other personal items can be cleaned with wipes.

The agent in question (identified only as Novichok, a family of chemicals) has been described as the most potent ever made.

How is it that ordinary cleaning can suffice as a method of decontamination? Is it a very unstable molecule? Does water (or detergent, or detergent solution, or alcohol solution) act strongly to decompose such chemicals? If unstable in water, how can it remain stable in the body to act? Could any viable agent remain in the wash waste water (going down the drain) after washing and pose a hazard downstream?

Edited:

The focus of my question is entirely about the apparent paradox of a chemical able to remain stable in an everyday environment, yet readily destroyed/decomposed by everyday means. In the specific case, a chemical which happens to be lethal in trace quantity that can persist, yet simple washing apparently destroys all trace, removing any potential for harm.


texts:
What is the IUPAC name of isocyanide : isonitrile or carbylamine?

Are "methyl isocyanide" and "carbylamine" the same thing?


texts: How to rationalise the IUPAC name for tetrahedrane?

texts: I'd like some assistance in understanding the IUPAC name for tetrahedrane. I understand the basics of polycyclic ring naming however this example has me confused.


texts: Can someone explain the unintuitive ordering in the metallic activity series?

texts:
I would understand it if the metallic activity series Li, Cs, Rb, ... Pt, Au corresponded to electronegativity or ionization energy. However, the way it is written, lithium will displace caesium, while caesium will displace rubidium (it goes from the top of family 1 to the bottom and then up again).

This order seems so random. Is there any order to it or is it just determined experimentally through trial and error? In addition, wouldn't different valences on the metals affect their placement in the series?


texts: In what case would water attack the least substituted carbon in an oxymercuration–demercuration reaction?

texts:
I understand that oxymercuration–demercuration is textbook Markovnikov. However, in a case like this, where the $\ce{OH}$ is formed on the least substituted carbon (secondary) rather than the most substituted (tertiary because of the methyl group), what could be the explanation?
I thought that $\ce{H2O}$ always attacks the most substituted carbon which is why $\ce{OH}$ forms there.


texts: Is it possible to retain the stereo-information when using enantiopure compounds?

texts: In a reaction, there is always a probability that the product will be a racemic mixture of the product's enantiomers. Is it possible to use only certain enantiomers in order to achieve just one enantiomer of a product? That is, would using only the D enantiomers of certain compounds ensure getting the D enantiomer of the product?


texts: Typical reaction yield for combustion of hydrogen

texts:
I am writing an essay on the chemistry of rocket fuel, and I was wondering what, if any, would be a commonly accepted value for the actual yield of the reaction between hydrogen, $\ce{H2},$ and oxygen, $\ce{O2}.$ I would also love it if you could cite some sources so I can find more information on this exothermic reaction:

$$\ce{H2 + O2 -> H2O + heat}$$


texts: What exactly is hydrogen bonding (and does it really need fluorine, oxygen, or nitrogen)?

texts:
I'm not satisfied with the rationale for the intermolecular attraction known as hydrogen bonding. In my book, it states that

  Hydrogen bonding is a special type of intermolecular attraction between the hydrogen atom in a polar bond (particularly H ¬ F, H ¬ O, and H ¬ N) and non-bonding electron pair on a nearby small electronegative ion or atom usually F, O, or N (in another molecule).

It seems that chemists looked at the data and found they needed a 'fudge factor' to fit the higher boiling points of ammonia, water, and hydrogen fluoride.

Why doesn't hydrogen bonding apply to other atoms like Sulfur or Chlorine? They seem to be electronegative enough IMO. Is there an explanation that explains why this is, rather than saying that it's there? What makes Hydrogen so special?

Note: Chlorine is more electronegative than Nitrogen.


texts: Shouldn't it take more energy to break CO2 compared to CO?

texts: I read in a book that bond dissociation energy of carbon monoxide $(\ce{CO})$ is $\pu{749 kJ/mol}$ and carbon dioxide $(\ce{CO2})$ is $\pu{532 kJ/mol}.$ Shouldn't it take twice as much energy to break $\ce{CO2}?$


texts: Finding out more stable conformer via molecular orbital interaction

texts:
Out of these two, which one is more stable? I'm unable to imagine the orientation of the lone pairs of O and ABMO of C and Cl bond.

Any tips to tackle these kind of problems?


texts: Why does NaBH4 reduce double bonds conjugated to carbonyl groups, while LiAlH4 does not?

texts: I have been going through reduction of aldehydes using $\ce{LiAlH4}$ and $\ce{NaBH4}$. If there is a double bond conjugated with the carbonyl group, $\ce{LiAlH4}$ doesn't reduce it, leading to an allylic alcohol. However, using $\ce{NaBH4}$, some of the fully reduced alcohol will also be formed. Why is this so?


texts: Extraction of a pyridine tetrazole from the aqueous phase

texts:
I have synthesised a compound which is basically a pyridine ring connected to a tetrazole. The procedure suggested to precipitate it at pH 1, but it did not precipitate. It then suggested to extract it with ethyl acetate.

The problem is that it is not going to the organic layer but into the aqueous layer. I have tried both at pH 1 and 7 and it still does not move to the organic layer.

Any ideas how to solve this problem?


texts: What additive can I add to Jelly Wax/Gel Wax to increase its cooling time/setting time?

texts:
Jelly Wax. Jelly wax, also commonly known as gel wax, is a clear, dimensionally stable, jelly-like material made from specially processed mineral oils. It can be used to create a variety of special effects and is also suitable for making decorative container candles. It is normally heated until it liquifies and then poured into a mould. It sets quickly back into a jelly.

I want to use it to pour into a transparent PVC pipe for a sculpture. Unfortunately I have found that it cools rather quickly for it to be useful for this purpose.

Anyone knows how I can increase the cooling time, using an additive maybe?


texts: Does the largest known cycloalkane contain 288 carbon atoms?

texts:
If you Google "largest known cycloalkane", you will find this result:

For context, there has been discussions on "largest known alkane". There is a related chem.SE question. There is also a scientific paper on it. The paper says that the longest linear alkane is $\ce{C59H120}$. OTOH, the Wikipedia article for cycloalkane mentions that the larger cycloalkanes, with more than 20 carbon atoms are typically called cycloparaffins. So, there has to be a known "cycloparaffin" with highest number of carbon atoms.
The above result came from a random HW-QnA site. From where does the result come from?
Question: Does the largest known cycloalkane really contain 288 carbon atoms? If not, how many carbon atoms are there in the largest cycloalkane that has been actually observed and isolated?


texts: What is most efficient method of lowering freezing point of amines without greatly effecting properties? Method must involve incorporating an additive at small percentage.


texts: Is there a free, super simple app or website for IUPAC names from structures?

texts:
I am looking for a free, very simple tool for IUPAC names of organic molecules.

I teach high school chemistry, and it would be fantastic to have an app or web tool that students could use to draw molecules and verify the systematic names of branched alkanes and simple alcohols, aldehydes, ketones, possibly acids; simple ethers, esters, cycloalkanes would be nice but aren't strictly necessary.

I do have MarvinSketch, but I find it too complex for absolute beginners, both to install and to use.
Chemdraw JS does not work well on mobile.

Suggestions?


texts: Does (2-fluoroethyl)benzene undergo elimination via E1cb or E2?

texts:
I have seen in two different sources claiming that $\ce{PhCH2CH2F}$ gives styrene $\ce{PhCH=CH2}$ when treated with alcoholic $\ce{KOH}$, but one source suggests an E1cb mechanism, while the other suggests an E2 mechanism.

I think that the phenyl group should not be able to promote the formation of a carbanion in an E1cb mechanism. All the examples of E1cb mechanisms I have seen involve deprotonation of compounds which have $\mathrm{p}K_\mathrm{a}$ values of 20 or less, and toluene does not fit this.


texts: Why is it that tertiary alcohols cannot be oxidized? I was told that it's because there is no hydrogen to remove, but I don't understand why another OH could not be formed where there is a C-H bond.


texts: Bond length and bond strength correlation

texts: Is bond strength inversely proportional to bond length? As the bond length decreases, does the bond strength increase?


texts: Why is the equilibrium constant increasing in this exothermic reaction?

texts:
A problem asks, if you have a positive $\Delta S$ (positive change in entropy) for an exothermic (meaning a negative $\Delta H$, or negative change in enthalpy) reaction and temperature increased, what would happen to $K_{\mathrm{eq}}$ and $K_{\mathrm{eq}}/Q$ (where $K_\mathrm{eq}$ is the equilibrium constant and $Q$ is the reaction quotient)?
The answer states that $K_{\mathrm{eq}}/Q$ and $K_{\mathrm{eq}}$ would increase. This is because if you use the thermodynamic equation, $\Delta G = \Delta H - T \Delta S$ (where $\Delta G$ is the change in Gibbs free energy and $T$ is for temperature), as you increase temperature you get a more negative number (since $\Delta S$ is positive and $T\Delta S$ is being subtracted). This would lead to a more negative $\Delta G$. Then, using another thermodynamic equation, $\Delta G = RT\ln(Q/K_{\mathrm{eq}})$ (where $R$ is the ideal gas constant), if $\Delta G$ is decreasing (becoming more negative), then the term $(Q/K_{\mathrm{eq}})$ must also be going down. This means that $K_{\mathrm{eq}}/Q$ must be going up and therefore $K_{\mathrm{eq}}$ increases, as temperature increases for this exothermic reaction.
So my issue is, I thought for an exothermic reaction, where heat can be represented as a product, I thought increasing the temperature would shift the reaction to the left and decrease $K_{\mathrm{eq}}$. Could someone clarify this for me? I tried looking this up with Chemistry Libretexts, but it didn't seem to clarify anything. The table seemed to suggest that we do use heat as a component of the reaction in endothermic or exothermic reactions to predict the $K_\mathrm{eq}$ change.


texts: How to calculate the pressure of an ideal gas that undergoes isothermal expansion?

texts:
A 2.35 mole sample of an ideal gas, for which $C_{\mathrm{m},v}=3R/2$ initially at $\pu{27 ^\circ C}$ and $\pu{1750 kPa}$, undergoes a two stage transformation. For each of the stages described in the following list, calculate the final pressure as well as $q$, $w$, $\Delta U$ and $\Delta H$. Also calculate $q$, $w$, $\Delta U$ and $\Delta H$ for the entire process.
(a) The gas is expanded isothermally and reversibly until the volume triples.
(b) Beginning at the end of the first stage, the temperature is raised to $\pu{105 ^\circ C}$ at constant volume.

Since the process is isothermal, $\Delta H = 0$. In order to calculate the final pressure. I use the formula,
$P_\mathrm{i}V_\mathrm{i}^{x} = P_\mathrm{f}V_\mathrm{f}^{x}$,
where $x = C_{\mathrm{m},p}/C_{\mathrm{m},v}$.
Hence $x = 5/3$. I then substitute this into the formula to get
$$P_\mathrm{i}V_\mathrm{i}^{5/3} = P_\mathrm{f}V_\mathrm{f}^{5/3}.$$
Since the volume triples, $V_\mathrm{f}/V_\mathrm{i}=3$, hence manipulating the formula I got
$$P_\mathrm{i}/P_\mathrm{f}=3^{5/3}$$
and since $P_\mathrm{i}=\pu{1750 kPa}$, I substitute this into the above equation to get $P_\mathrm{f}$, which answers the first part of the question.
However I don't seem to get the right answer, hence I could not continue doing the question. Could anyone explain?
Also, am I right to say that we use
$P_\mathrm{i}V_\mathrm{i}^{x} = P_\mathrm{f}V_\mathrm{f}^{x}$
for an reversible adiabatic process only.
$w = -nRT\ln\left(T_\mathrm{f}/T_\mathrm{i}\right)$ for an isothermal process and
$\Delta U = nC_{\mathrm{m},v}(T_\mathrm{f} - T_\mathrm{i}) = -P_{\text{external}}(V_\mathrm{f} - V_\mathrm{i})$
for a non-reversible adiabatic process.
Im rather confused as to decide under which conditions should I use each of these three formulas.


texts: Why does vapor pressure of ice decrease faster than water when temperature decreases?

texts:
In melting point depression, I have learnt the explanation from the textbook that (e.g. aq. solution):
Definition of melting point: ice and water exist in equilibrium (have the same vapor pressure).
(1) aqueous solution generally has a lower vapor pressure than the pure solvent (water)
(2) Vapor pressure of ice drops faster than water when temperature drops
Therefore, at 0°C, the vapor pressure of water in aq. solution is lower than ice. When the temperature drops below 0°C, the drop in vapor pressure of ice can 'catch up' with water, hence an equilibrium can be reached i.e. melting point depression.
Question: I would like to know what is the rationale behind (2) since I have no idea on how to explain its validity.
Thank you.


texts: How would one calculate the entropy change for an adiabatic irreversible process?

texts:
If two states $A$ and $ B$ are connected by a reversible path, they can never be connected by an irreversible path during an adiabatic process because:

$\underbrace{\Delta U}_{\text{state function}} = \underbrace{\Delta W}_{\text{path function}}$

And $W_{\text{reversible}}\neq W_{\text{irreversible}}$

Now, Atkins' Physical Chemistry (Section $3.2$) states that:

  To calculate the difference in entropy between any two states of a system, we
  find a reversible path between them, and integrate the energy supplied as heat at each
  stage of the path divided by the temperature at which heating occurs.

But the problem is that we cannot define a reversible path for an adiabatic irreversible process. If that's the case, how can we calculate the entropy change for an adiabatic irreversible process?


texts:
Polar solvents love polar solutes to be dissolved in it and non polar with non polar. Often said as like dissolves like.

Okay, polar loving polar can be understood with help of the facts: same polar nature, same kind of interactions etc.

But how will you explain the application of this rule with organic or non-polar solvents?

Solomons’ and Fryle’s Organic Chemistry says that there are some unfeasible entropy changes when polar solutes are added in non polar solvents and vice versa.

Why so?


texts: Why does latex tubing become white and brittle over time, especially where it's bent?

texts:
Here's a picture of some latex tubing we have in the lab, bought many years ago and stored in a drawer.

What's responsible for the white corners near places where the tubing is bent? Is this dehydration, oxidation, an aging effect accelerated by stress, or something else?


texts:
I need some help in a electrophilic substitution reaction.

What will be the major product formed in this reaction and why?

I know that
(1) Activator wins over deactivator.
(2) A powerful wins over a weak activator.
(3) When a substituent possesses a lone pair, it it usually extends the product determining influence.
(4) Steric factor always plays a key role.

$\ce{NO2}$ is a powerful deactivator, so I think the middle ring will not undergo substitution. I can't decide which of the other two rings will undergo substitution and at what position.


texts: In a heating curve, when it is plateau, where does all the energy go since the temperature does not get higher?

texts: So between the change of phases within the matter(solid liquid gas), the temperature reaches a plateau, no matter how much heat you add to it, it just stays the same. Where did all those energy go?


texts: I learned that when $PbO$ is hot, it is orange. When $PbO$ is cold, it is yellow. I know this's called thermochromism. But how do that happen? Is it because the ions inside doing something?


texts: Molecular Orbital Theory and No. of bonds

texts:
The order of filling of molecular orbitals $\ce{O2}$ by MOT is this :

But from it, how can I deduce that there is one sigma and one pi bond in an oxygen molecule ?


texts: availability of database for vibrational spectroscopy

texts:
is there a database for vibrational spectrums of molecules available?
i have recently started working with fragrant molecules and I am interested in their vibrational spectrums. i am limited by the facilities right now and would like to know if there is a database available so that I can begin working without delay.
Any software used for the same would also help.


texts: Confusion about orienting effects in o-chlorotoluene

texts:
I'm confused about where the next substituent in the electrophilic substitution of o-chlorotoluene will land. My question comes on the background of having 3 different sources of information that say different things.
The first one is my teacher: she taught us that at the nitration of ortho-chlorotoluene, the $\ce{NO2}$ group will be placed in the 4 position, giving 2-chloro-4-nitro-toluene. This seems reasonable, but even more reasonable seems the second source. That is this website, which shows that the product will be 2-chloro-5-nitrotoluene (3rd image, example 2).
The 3rd source is completely confusing, giving little citation as I was not able to find the material cited online. I'm talking about a question on this website here, but I am not sure if I can trust it, that is the reason why I'm adding another question.

So, can someone please explain me what is the actual product?


texts: Why doesn't lithium form dilithium crystals? (Calling Mr.Spock)

texts:
Hydrogen is in the first column of the periodic table. At STP it is a diatomic gas. When cooled and/or under pressure it forms a crystalline solid of di-hydrogen molecules. Calculations indicate that under high enough pressure it may form a monatomic basis metallic crystal, and scientists are actively looking to find evidence of this. Results so far seem inconclusive.

However, lithium is also a first column element. But its solid is a monoatomic basis metal and NOT a dilithium crystal as we would expect based on hydrogen. Why not?


texts: What is the reason for the anomalous electronic configuration of palladium?

texts: The p block elements generally have the general valence shell configuration as $$n\mathrm{p}^{1-6}\,n\mathrm{s}^{1-2}.$$ Expected electronic configuration for palladium is $$\ce{^46Pd} = \mathrm{1s^2\, 2s^2\, 2p^6\, 3s^2\, 3p^6\, 4s^2\, 3d^{10}\, 4p^6\, 5s^2\, 4d^8}.$$ But I find that it's valence shell instead is $$\mathrm{4d^{10}\, 5s^0}$$ I first thought, for achieving fully filled d-subshell, 2 electrons go to the d-subshell from s-subshell. This electron transfer should happen for all members of its group, yet only palladium demonstrates this. Why is this so?


texts: Why doesn't Nitrogen monoxide dimerize even though there is an odd electron present whereas nitrogen dioxide does (because of the odd electron on nitrogen)?


texts: What is the electrolytic bath used in gold-plating of copper articles?

texts:
The answer is $AuCl_3 + NaCN$

Now I understand that for electroplating, we need gold to be deposited on the copper article, and the electrolyte must enable that deposition. But I don’t know what is the use of $NaCN$ in the process.

Also, if copper is the cathode, then pure gold should be the anode. But the oxidation potential of gold is very low, then how does it get dissolved in the solution.

Can I get an explanation on this process would work?


texts: How are the Cahn-Ingold-Prelog rules applied to chiral molecules without a stereogenic carbon center? i.e biphenyls and allenes

texts: It's easy to apply CIP rules to chiral carbons but what about in chiral molecules without these carbon cneters like biphenyls, sulphoxides and allenes? Are they applied at all?


texts: How is the process of creating PVC fabrics harmful for the environment?

texts: I often hear that the production process for PVC fabrics (such as those used in Gucci and Versace handbags) is very harmful to the environment. What part of the process is harmful and can this be prevented?


texts: What is CIF (a PCB developer) and what does it do?

texts:
I made a PCB (printed circuit board) for the first time, and the process included covering the board with the shape we want, exposing the board to UV light and then putting it in a developer which removes the part of the resin that was exposed to the UV radiation.

My question is, what is this developer? I think it has the commercial name of CIF (http://uk.farnell.com/cif/ar46/developer-ready-for-use-1l/dp/1783557), but what is it really? What does it do to the board and why only to the UV-exposed part?

Thanks!


texts: Finding out the value of rate constant on titration

texts:
The question goes as follows

Consider the reaction $$\ce{X(aq) \longrightarrow Y(aq) + Z(aq)}$$

The above reaction is titrated with a reagent $A$ and all of $X, Y, Z$ reacts with $A$ with the ratio of 'n' factors of $X, Y, Z=1:2:3$

here n factor refers to change in oxidation number of substance per mole of the substance on titration with $A$

The following data was obtained.

The question is to find out the value of rate constant considering the titration reaction to be first order.

The value of rate constant is given by $\frac{0. 693}{t_{1/2}}$ So I have to find out half life of the reaction . I am facing trouble finding out since the rate of voume of A required depends on the amount of substance present at that instant. Any help shall be highly appreciated. Thanks.


texts: Do strong acids actually dissociate completely?

texts: Do strong acids actually dissociate completely (every single molecule dissociates), or are they just assumed to do so for the sake of simplicity? That seems odd, considering weak acids, many of which are very similar to strong acids, don't fully dissociate.


texts:
I read an article by popsci that talked about huge fans forcing methane over a catalyst.

Now that got me wondering, can't we produce hydroxyl radicals with powerfull uv lasers blasting the sky, creating more hydroxyl radicals to break down the methane.

Would this be effective enough to help create enough hydroxyl radicals to help break down methane or would it be a waste of energy against too small an offset?


texts: How to name binary (inorganic) compounds given their chemical formula, and vice-versa?

texts:
I wish to understand how to name binary (inorganic) compounds when given their formula. When I am a given compound like $\ce{B2F2}$ or $\ce{N2O4}$, I have little to no clue on how to write their chemical names. Similarly, I also trip up when trying to convert a given chemical name - say diboron difluoride - to its chemical formula.

Moreover, I have seen that a few times we do not need the numeric prefixes - as in lithium oxide or magnesium chloride - but sometimes we do - as in dinitrogentetroxide or iodine monochloride. So, I also need help understanding when to include numerical prefixes and when to not.

Please limit the answer to simple, binary, ionic and covalent compounds, and exclude hydrocarbons.


texts: How to check which compound will show optical isomerism?

texts:
So my teacher told that those compounds which have one or more chiral carbon present in them it will definitely show optical isomerism because it has an optically active stereoisomer, but there are many compounds which do not have any  chiral centre like, how will you determine which shows optical isomerism among the following.

(1) https://pasteboard.co/J73FtBo.jpg

(2) https://pasteboard.co/J73FDnl.jpg

(3) https://pasteboard.co/J73FN9N.jpg


texts: Plotting the Arrhenius curve without the rate constant

texts:
I was carrying out an experiment about finding the activation energy of the Maillard reaction using the Arrhenius equation. Since I didn't know the rate constant for the reaction due to the complex reaction mechanism of the Maillard Reaction, I tweaked the rate reaction to fit into the Arrhenius reaction.
$$\text{Rate}=k[\text{glucose}]^m[\text{asparagine}]^n \\\implies k=\frac{\text{Rate}}{[\text{glucose}]^m[\text{asparagine}]^n } \\\implies k=([\text{glucose}]^m[\text{asparagine}]^n)\,\frac{\mathrm d[\text{product}]}{\mathrm dt} \\\implies k=\frac{c}{t}$$ where $c=([\text{glucose}]^m[\text{asparagine}]^n)\,\mathrm d[\text{product}]$. By ln both sides, I got $\ln k=\ln c-\ln t$ which I then subbed into the Arrhenius equation to get $$\ln c-\ln t=-\frac{E_\mathrm a}{R}\times\frac{1}{T}+\ln A$$ By manipulating, I got $$\ln t=\frac{E_\mathrm a}{R}\times\frac{1}{T}-\ln A+\ln c$$ Which then produce the below graph based on the experimental data
However, the gradient is positive which technically should be negative according to other Arrhenius plots I have seen. Does anyone know if this is correct or is there something I missed out?


texts: What are energies in computational methods relative to?

texts:
As per my understanding, in molecular mechanics (MM) the computed strain energy is based off the strain inherent in the molecule under study relative to an idealized form. For example, cyclobutane to its acyclic form.

However, what about computed values from other methods like PM6 energies, HF energies or MP2 enthalpies. What are these computed values relative to?