texts: Is there a commonly agreed threshold at which a compound is considered "insoluble" or "soluble"?

texts: I'm doing a literature review on solubility prediction and this is a bit of information that surprises me in its absence. The only information I've found is through Wikipedia with 0.1 g per 100 ml, but that source throws up a 403 Forbidden and seems to be a university's course notes.


texts: Why do amino acids hydrogen bond rather than ionic bond when they are forming secondary structures in proteins?

texts:
When peptide bonds are formed between amino acids, electron delocalisation causes the N to be more positive and the O to be more negative. As a result, why does 'hydrogen bonding' occur to form secondary structures such as alpha helices and beta pleated sheets, rather than 'ionic bonding'?

Is this simply a case of semantics, or is it the lack of transfer of an electron that makes the distinction between the two?


texts: Friedel-Crafts Alkylation Using Alkenes: Mechanism

texts:
What is the mechanism by which benzene, cyclohexene and $\ce{AlCl3}$ form cyclohexylbenzene?

I believe that cyclohexene will form a bond with Al with its double bond. However, how do we get rid of the $\ce{AlCl3}$ now attached to the previous cyclohexene after the benzene attaches to the module?


texts:
The question is to find out the pH of $\pu{0.01M}$ glycine solution. It is given that $K_\mathrm{a1} = \pu{4.5*10^{-3}}$ and $K_\mathrm{a2} = \pu{1.7*10^{-7}}$.

Glycine is $\ce{NH2CH2COOH}$. The two $K_\mathrm{a}$ values correspond to the ionization of $\ce{COOH}$ and  $\ce{NH2}$. My idea was to average the two $K_\mathrm{a}$ values and take log to get pH. However this is not yielding the correct answer.


texts: Converting benzoic acid into meta-fluorobenzoic acid

texts:
How do I convert benzoic acid to meta-fluorobenzoic acid in not more than 3 steps? I did it but the process was a little too long.
Here is my attempt


texts:
Leucine is a type of amino acid. Let me write its chemical formula as $\ce{NH2-C5H10-COOH}$. On the wikipedia page, https://en.wikipedia.org/wiki/Leucine, there are two dissociation constants, one for $\ce{-COOH}\,$ given by $\mathrm{pK}_{a1}=2.36$, and one for $\ce{-NH3+}$ given by $\mathrm{pK}_{a2}=9.60$. But I also know that once $\ce{-COOH}\,$ loses its proton $\ce{H+}$ into the solution, the proton may combine with the $\ce{-NH2}\,$ group of the same molecule to form the zwitterion $\ce{NH3+-C5H10-COO-}$ so that the solution now has $4$ species with $4$ dissociation equilibria

$$\begin{array}{rclll}
\ce{NH3+-C5H10-COOH}\!\!&\!\!\ce{<=>}\!\!&\!\!\ce{NH2-C5H10-COOH +H+},& \ &(1)\\
\ce{NH3+-C5H10-COOH}\!\!&\!\!\ce{<=>}\!\!&\!\!\ce{NH3+-C5H10-COO- +H+},& \ &(2)\\
\ce{NH2-C5H10-COOH}\!\!&\!\!\ce{<=>}\!\!&\!\!\ce{NH2-C5H10-COO- +H+},& \ &(3)\\
\ce{NH3+-C5H10-COO-}\!\!&\!\!\ce{<=>}\!\!&\!\!\ce{NH2-C5H10-COO- +H+}.& \ &(4)
\end{array}$$

So there should be $4$ equilibrium constants. Which two do $K_{a1}$ and $K_{a2}$ refer to and how do I know the other two? Or is it that we can assume that $\ce{-COOH}\,$ and $\ce{-NH3+}$ dissociate independently so that the equilibrium constants of the $4$ equations are $K_{a2},K_{a1},K_{a1},K_{a2}$ respectively? I've also seen in some calculation that the zwitterion $\ce{NH3+-C5H10-COO-}$ and the original molecule $\ce{NH2-C5H10-COOH}$ are treated as the same species. But I don't quite understand why this is allowed. They clearly have different charge distributions and should be treated as distinguishable particles in entropy (or Gibbs free energy) calculations.


texts: How to identify an emerald green solution with possibly two anions?

texts:
The solution is emerald green in colour.
When added with water, it gives a pale blue solution.
When reacted with $\ce{BaCl2}$, it gives a sky blue solution and a white precipitate.
When reacted with $\ce{AgNO3}$, it gives a sky blue solution and a white precipitate.

This does not make any sense to me. The $\ce{BaCl2}$ is used to test sulphates ions and $\ce{AgNO3}$ is used to test halides. How could you have two negative ions?


texts: Why, in titration, is universal indicator not commonly used?

texts: My teacher said that we always used indicators such as methyl red, methyl orange, litmus, phenolphthalein, etc. rather than universal indicator. I don't understand why, though, would not universal indicator serve the same function, but for essentially all titrations rather than select few?


texts: Symmetries of the v=0 and v=1 quantum harmonic oscillator wave functions and those of the Cartesian Coordinates (References)

texts:
I'm busy with a writing project for my third year Chemistry course and in the project one of the things we need to consider and answer is the symmetries of the v=0 and v=1 quantum harmonic oscillator wave functions and those of the Cartesian Coordinates. This question falls under the suh-heading (in the project) 'Determination of IR-activity of normal modes and the prediction of spectra'.

Now I'm not expecting anyone to give me the answer to this question, but I would greatly appreciate it if you could let me know of websites and/or accessible textbooks that I can use to find this answer. I still have two months to complete the writing project and am essentially done with it, but its just this question that I have been really struggling to answer since I can't seem to find it online or in the textbooks by Atkins and Engel & Reid respectively.

Any help would be appreciated, Thanks in advance.


texts:
In this question, the user asked about curing sodium silicate with calcium chloride. My question is, will the resultant product be insoluble in water? I know calcium silicate is only very slightly soluble, but I'm expecting it's going to be a bit more complicated than that.
I'm not a chemist, and wanted to know the answer to something I'm messing with at work to know if I need to hire a materials professional.


texts: Why is copper(II) sulfate added drop by drop during the Biuret test?

texts:
The Biuret test is a test for proteins.  The procedure is to add a strong base, such as NaOH, to dissolve the protein.  After that, copper(II) sulfate is added drop by drop into this until a (violet) colour change is observed.  I have a few questions.

How does NaOH dissolve the protein exactly?
What is the significance of adding copper(II) sulfate drop by drop?
How would the reaction vary if copper (II) sulfate was added first and NaOH added subsequently, drop by drop?


texts:
I am trying to monitor the esterification of a non UV active amino acid.I used thionyl chloride and Methanol as reagents.

As amino group is unprotected, Ninhydrin should give positive result for both reactant and products. However, I believe there should be Rf difference between reactant and product.When I performed TLC and stained with ninhydrin, the reactant was strong brown and one spot at very high Rf value showed pale brown coloration.Now can I think that pale brown spot as my target ester?

I am doubtful because reactant and product both supposed to show strong coloration as amino group is not affected.On the other hand,  will just methylating the acid result in high Rf change? Because I feel amino group is also polar, it would not allow spot to raise till high Rf end.


texts: Why don't ligands affect the oxidation state of the central metal ion?

texts:
If $\ce{Fe^3+}$ were complexed with 6 $\ce{H2O}$ ligands, the resulting complex ion would be $\ce{[Fe(H2O)6]^3+}$, and the central metal ion would still have the same oxidation state of +3 as it did before complexation. However, didn't the $\ce{Fe^3+}$ ion receive 12 electrons (2 from each water molecule) in forming the complex? Is this not a kind of reduction?

Also, is the positive charge of the complex ion still localized on the metal ion, or is it spread over the entirety of the complex?


texts: Finding the pressure equilibrium constant of the reverse reaction

texts:
At $1000~\mathrm{K}$, $K_\mathrm p = 1.85$ for the reaction.
  $$\ce{SO2 + \frac12O2 <=> SO3}$$

  What is the value of $K_p$ for the reaction
  $$\ce{SO3 <=> SO2 + \frac12O2}$$

Now, since the task gives us $K_\mathrm p$, it seems strange to ask for it again with the equilibrium put the other way around. Does this make sense? Is it a typo? Either that or my understanding is flawed. It would make more sense to ask for $K_\mathrm c$.

The chapter has this equation: $K_\mathrm p = K_\mathrm c(RT)^{\Delta n}$, I think this is relevant given the temperature is available to solve it.

Source: task 15.21 in the 11th edition of Chemistry: The Central Science, and the answer is suppose to be $0.541$.


texts: Stability of geometrical isomers in cycloalkanes

texts:
Among the following, which should be the most stable compound?
1)Cis-cyclohexane-1,2-diol
2)Trans-cyclohexane-1,2-diol
3)Cis-cyclohexane-1,3-diol
4)Trans-cyclohexane-1,3-diol

My thought process is-cis isomers with adjacent OH groups lead to Hydrogen bonding so 1) should be the most stable, I'm not sure if repulsion will be the dominating factor and change the answer- what is the correct way to think about this?


texts: Nomenclature for stereoisomer example possible wrong?

texts:
I understand the principal of the Cis-Trans naming system (at least I think so), until I saw this example in my learning material. My teacher doesn't know either so I thought I would post it here.

This is the molecule:

There are two ethyl groups both on the bottom side of the double bond, so it could be cis right?

Apparently not, the book says this is the answer:

Could someone please explain the reasoning behind this? This particular example is unusual because there are three ethyl groups attached to the double bond so I cannot determine which one should be the parent chain. The book doesn't explain.


texts: Shouldn't all of group 16 form double bonds?

texts: I notice that out of all of group 16 oxygen is the only element that can form a double bond. Why is that because shouldn't all of group 16 be able to form a double bond and be diatomic because they all have six valence electrons?


texts: How many decimal places should a volume measurement in a beaker include?

texts: I have a beaker which goes up in $0.5~\mathrm{mL}$ increments and my teacher told me that my measurement $(15.50~\mathrm{mL})$ was incorrect, and instead the answer was $15.5~\mathrm{mL}$. I don't understand. I know that the liquid is between $15.5~\mathrm{mL}$ and $16~\mathrm{mL}$. My estimated digit is $0$ (it looks like it lies on the line), so my answer is $15.50~\mathrm{mL}$. How is it $15.5~\mathrm{mL}$?


texts: Manipulate melting point of frozen water

texts: How to manipulate water in way that ice melting point isn't 0°C, but for example 4°C?


texts: reaction with Barium Chromate, Potassium nitrate

texts:
I'm confused, in the reaction:$$\ce{K_2CrO_{4(aq)} + Ba(NO_3)_{2(aq)}\rightleftharpoons BaCrO_{4(s)} + 2KNO_{3(aq)}}$$
I got a white precipitate in an opaque yellow solution and I was told that the white precipitate was $\ce{BaCrO_4}$ but while searching on Internet I found that its color is yellow, and that the $\ce{KNO_{3(aq)}}$ is white, so my question is what is true? or what causes the color of the final solution?


texts: Where can I find CAD blocks for lab glassware?

texts: I want to draw a sketch of my apparatus for my report. I am conversant with the AutoCAD drafting software. Where can I download CAD blocks for commonly used labware items (like round bottom flask, allihn condensor, drying tube, heating mantle, retort stand, etc.)?


texts: Is the pH of a solution (orange juice) affected by the presence of a metal?

texts: Is the pH of a solution (orange juice) affected by the presence of a metal (aluminium, tin or iron for example)? I know that the metal will corrode in the presence of an acid (citric acid in this case), but will the metal have any effect on the actual acidity of the solution?


texts: What is Vorlander's rule? I have got it from a book all of a sudden, but without any further information about it; could you please explain it a bit?


texts: I drink city water, city has lead pipe, how is this safe?

texts:
6 years ago, I needed to replace the main water shut off valve to my house.  This required the city to turn off the water at the street. Incompetent city employee drives key through water pipe. Plumbers fix pipe, I realize that pipe is lead.

Yearly, the city (90% of which was built before 1950) sends out a water quality report, which reports undetectable amounts of lead.  That is interesting since probably 90% of the city has lead pipe.

Several questions :

How is lead pipe safe from leaching lead into water?
Do cities usually treat the water to prevent lead from leaching into the water?
What is the form of harmful lead (e.g. is it in aqueous solution, lead oxide, or forming  ligands with some other molecule)?


texts: This is a follow-up to the question here.  There is no mono-anionic stage shown, does it "disproportionate" to the neutral molecule and the di-anion?


texts: Why are rare earth metals and platinum group metals are often found clustered together in ores

texts:
Rare earth and platinum group metals are often found clustered together in the earth's crust. Mining for platinum, for instance, also yields Rhodium and Ruthenium belonging to the same group. Likewise, rare earth elements such as Neodymium, Europium and Samarium also cooccur together in the same ore so much so that they are difficult to chemically separate.
It could be reasoned that it's the result of nucleogenesis where elements are formed consecutively based on their atomic number. While it might explain the first row and the second row of each group, where each metal is only one atomic number apart, it doesn't explain why metals from both rows are found together which are much further apart.
Alternatively, the similar chemistry of each group could explain the clustering. The two groups are the only group with this property. It fails to explain, however, how these metals found each other in a molten soup of heterogeneous elements. There may be some geological factors in the clustering, but it's unclear.
Why are the two groups of elements found clustered together?


texts: Why does dielectric constant of crystal fluctuates in case of Frenkel defect in a crystal?

texts:
So I was studying Frenkel defect in crystal and came across this line that said

  The closeness of like charges tends to increase the dielectric constant of the crystal.

I'm not able to understand it properly because in a dielectric an number of dipoles align themselves in a direction parallel to electrical field and thus they create a counter field to reduce the electric field that created or aligned it. Now, if we think like that here, dipole moment is charge multiplied by distance, and distance has definitely reduced between a positive and negative ion here, so dipole moment should decrease and consequently dielectric constant should decrease but why is the opposite happening here.


texts: What is the chemical structure of ceramic nonstick coating on pans?

texts: There are lots of pans nowadays that have a ceramic nonstick coating instead of a PTFE coating. However I can not find anything online describing what kind of ceramic such nonstick coatings are. Does anyone have an idea what these nonstick ceramics are on a chemical level?


texts: Are the HKL planes for a primitive unit cell identical to that of the conventional unit cell?

texts:
Is there a general relation between hkl planes in primitive vs. conventional unit cells? For example, is (111) identical for both? To illustrate, let's say you took the planar packing density for (111) in the primitive unit cell and (111) in the conventional unit cell. Is the planar packing density equivalent? I'm inclined to think that the answer is no.
Related:

Wiki - Primitive Cell
Wiki - Miller Index


texts: Are all naturally occuring reactions exothermic?

texts: If a reaction is endothermic, then the reaction must take energy from the environment to occur (as far as I know), and if this is the case, then to me the reaction seems energetically unfavorable, as there is only so much energy you can get from the environment. Does this means all naturally occurring reactions, (that don't just happen once in a blue moon but at a steady rate) are exothermic? This seems pretty silly, so if not, why not?


texts: Does increasing the number of interferometers increase signal in FT-IR?

texts: I'm trying to understand why most modern FT-IRs have three interferometers. Does this improve the signal in someway or does it have another effect?


texts: What is the molecularity of a reversible reaction?

texts: I know that the definition of molecularity of a reaction is number of species reacting in an elementary step. But considering the theory of microscopic reversibility for elementary reactions, each reaction can be assumed to be reversible. In that case, if $$\ce{A <=> B + C}$$ then what is the molecularity of the reaction? Is it 1 or 2?


texts: I learned that solubility of substance increases with increase of temperature. But I came to know solubility of NaCl doesn't increase when temperature is increased . So what is the reason for this phenomena?


texts: What is the average distance of two different types of molecules of different concentrations in solution?

texts:
Concerning the simplest approximation for intermolecular distance in solution:
$d=(\frac{10^{24}}{cN_A})^{1/3}=1.18c^{−1/3}$
This applies for one type of molecule in solution. But, how to account for two different molecules A and B of different concentrations?
My case: I have molecule A of 0,4 uM and molecule B of 16x0,4 = 6,4 uM. The average distance A-A is therefore determined as 160 nm, average distance of B-B as 63,5 nm and average distance of any two molecules as 62,3 nm.
Is it possible to approximate the average distance of A-B as a weighed average of A-A and B-B, therefore (160+16*62,3)/17 = 69,2 nm, since any given molecule is 16-times more likely to be of type B than type A?
Thank you for your answers!


texts: Positive charge on a zwitter ion at pH=7?

texts:
I faced this question. But I am having some problems understanding the solution to this:

How can the negative charge on the peptide vanish on $\pu{pH = 7}$? Suppose, we have some $\ce{H+}$ donor on either $\ce{R1}$ or $\ce{R2}$. Then the $\ce{H+}$ donor can make the carboxyl radical neutral. But by donating a $\ce{H+}$ ion, the donor becomes negatively charged. Maybe, the donor can take the $\ce{H+}$ from the $\ce{NH3+}$ radical. But the result, a completely neutral tetrapeptide, doesn't satisfy the condition of the question.

Need a hint.


texts: Order of adding reactants on growth of Cu

texts:
I am reading the following paper which details the steps to control growth of Copper. They fabricate Copper powders from $\ce{CuNO3, NaOH, and C6H8O6}$. Specifically, in this paper they add the sodium hydroxide first to the copper nitrate solution and then they add the ascorbic acid. The chemical equations that occur are $$\ce{Cu(NO3)2 + 2NaOH -> Cu(OH)2 + 2NaNO3}\tag{1}$$
$$\ce{Cu(OH)2 + C6H8O6 -> Cu + C6H6O6 + 2H2O}\tag{2}$$

My first question is if the order of adding the acid and base was switched: first ascorbic acid was added to copper nitrate and then sodium hydroxide was added, would it yield the same products as (2)?

My second question is how could I calculate the theoretical pH of the overall reaction if I add 0.1M $\ce{CuNO3}$, 0.5M $\ce{C6H8O6}$, and 0.1 M $\ce{NaOH}$ following the procedure of the paper?

I am thinking that since NaOH is a strong base while ascorbic acid is a weak acid, the pH will be dominated by NaOH. Therefore, I think the pOH would be -log(0.1M $\ce{OH- from NaOH}$) and so the pH would be 14-1 = 13. However, I know this is too high a pH so my method is wrong. What am I missing?


texts: Why do foraminifera use less magnesium in their shells when the water is cold?

texts:
When scientists study ancient seabed cores, they say they can judge the temperature of the water in the past by analyzing the magnesium to calcium ratio in foraminifera shells (both in the form of carbonate, presumably).  Supposedly, they added less magnesium when the water was colder.

Why?  Is it because the lighter magnesium was more likely to be locked up in ice, like Oxygen-16 vis-a-vis O-18?

Also, why the focus on foraminifera?  Why not use diatom shells?


texts:
I need some clarification for the following assignment:

Derive the rate law for
$$\ce{A + B -> C -> P}$$
when $\ce{A + B -> C}$ is the slowest step and very slow.

My understanding is $\ce{A + B -> C}$ is the rate-determining step, so the rate law would just be
$$\mathrm{rate} = k[\ce{A}][\ce{B}].$$
I'm not sure if the question is asking about steady state approximation (SSA) or just a simple rate law. I know SSA happens if you assume the second step $(\ce{C -> P})$ is faster than $\ce{A + B -> C},$ meaning  $\ce{A + B -> C}$ is the slow step. I'm not so sure if my understanding of the question is correct.


texts: Oxidation state of iron ions in a unit cell

texts:
Consider UC (unit cell) for a cubic ionic lattice containing 4 oxide ions - what is the avg oxidation state for Fe ions in this lattice?

The four oxide ions create a -8 charge that must be counteracted by the iron ions. In a FCC unit cell, there are 3 total Fe ions per UC; therefore each ion must have a +8/3rds oxidation state.

Is this correct?


texts: Acid strengths for HBrO4 vs HIO4, and HBr vs HI

texts:
So I was looking at factors that control the relative strengths of acids and bases.

We know that $\ce{HI}$ is a stronger acid that $\ce{HBr}$ because $\ce{I}$ is a much larger atom.

But then, I read somewhere that $\ce{HBrO4}$ is stronger than $\ce{HIO4}$, because in this case it's electronegativity that plays the important role.

How do you know whether to use size or EN as a guideline for comparing strengths of acids/bases?


texts: How to identify the anode and cathode in a concentration cell?

texts:
How do I understand which is the anode and which is the cathode in this problem?

  We have a concentration cell with hydrogen electrodes. It's made up of two half-cells. One half cell contains [BaCl(aq)]=0.5 M, the other one has [BeOH(aq)]=0.5 M. Draw the cell diagram and calculate e.m.f at 25ºC

So I tried this:

$$\ce{Pt}(\ce{H2} \, 1~\mathrm{atm})| \ce{H+,\,Ba^{+2}} \,(0.5 M)||\,\ce{Be^{+2}}\, (0.5 M)|\ce{H2}(g,1~\mathrm{atm})|\ce{Pt}$$
I don't know how I should think to write the correct diagram. Can you please help me?


texts: What is the reason that vanadyl sulfate shows blue colour, even in its anhydrous form? If it's d-d transition, can you explain how it works in this compound?


texts: Are we limited to use only xy, yz and zx planes to check for planes of symmetry of a molecule? Because I see a plane of symmetry in  the following molecule through the two shown H atoms or OH groups. I am aware of the 3D structure shown by this projection. And since this molecule is Chiral, and has enantiomeric mirror image, this existence of a plane of symmetry appears contradictory.


texts: Explanation for the trends in nucleophilicity—Orbital interactions or electrostatic attraction

texts:
The trend of halide nucleophilicity in polar protic solvents is $$\ce{I- > Br- > Cl- > F-}$$

The reasons given by Solomons and Fryhle[1], and by Wade[2] are basically as follows.

Smaller anions are more solvated than bigger ones because of their 'charge to size ratio'. Thus, smaller ions are strongly held by the hydrogen bonds of the solvent.
Larger atoms/ions are more polarizable. Thus, larger nucleophilic atoms/ions can donate a greater degree of electron density to the substrate than a smaller nucleophile whose electrons are more tightly held. This helps to lower the energy of the transition state.

Clayden et al.[3] give the reason that in SN2 reactions, the HOMO–LUMO interaction is more important than the electrostatic attraction. The lone pairs of a bigger anion are higher in energy compared to a smaller anion. So, the lone pairs of a bigger anion interact more effectively with the LUMO σ*. Thus, soft nucleophiles react well with saturated carbon.

What I don't understand is the trend of halide nucleophilicity in polar aprotic solvents.

$$\ce{F- > Cl- > Br- > I-}$$

In aprotic solvents, only the solvation factor is absent. Bigger anions are still more polarizable and can interact in a better way with the LUMO. Then, what is the reason for the trend reversal in aprotic solvents? Solomons and Fryhle[1] say

  In these[aprotic] solvents anions are unencumbered by a layer of solvent molecules and they are therefore poorly stabilized by solvation. These “naked” anions are highly reactive both as bases and nucleophiles. In DMSO, for example, the relative order of reactivity of halide ions is opposite to that in protic solvents, and it follows the same trend as their relative basicity.

Shouldn't the orbital interactions matter more than the electrostatic attractions even in polar aprotic solvents? Why does nucleophilicity follow the basicity trend in polar aprotic solvents?

References:

Solomons, T. W. Graham; Fryhle, C. B. Organic Chemistry, 10th ed.; Wiley: Hoboken, NJ, 2011; pp. 258–260.
Wade, L. G. Organic Chemistry, 8th ed.; Pearson Education: Glenview, IL, 2013; pp. 237–240.
Clayden, J.; Greeves, N.; Warren, S. Organic Chemistry, 2nd ed.; Oxford UP: Oxford, U.K., 2012; pp. 355–357.


texts: Volume of air required to oxidize glucose

texts:
In the body, the oxidation of glucose is according to the reaction:

  $$\ce{C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O}$$

  Knowing that glucose consumption is $\pu{2.47 mol/d}$, What is the volume of air that must be breathed at $\pu{25 °C}$ to accomplish this oxidation for $24\ \mathrm h$ at the pressure of $1\ \mathrm{atm}$?

We are given:

  The atmosphere is composed of $21\,\%$ $\ce{O2}$ and $79\,\%$ $\ce{N2}$ (% volume).
  $R = \pu{8.314 J mol-1 K-1}$; $\pu{1 atm} = \pu{760 mmHg} = \pu{1.014e5 Pa}$.
  The molar volume of a gas at $\pu{298 K}$ is $\pu{24.45 l mol-1}$.

So, I have been a little stuck on this question. I have been trying to use the formula:

$$pV = nRT,$$

but it seems that I am missing something and I am not getting the right answer. It's possible that it might include molar fraction or partial pressure. I am confused.

The answer is $1\,724\ \mathrm l$. I would like to know how to get to this point.

Following the advice of @matt_black:

Here are my calculations that doesn't give me the right answer of $1\,724$ liters.

$$V_\mathrm m = 24.45\ \mathrm{l/mol}$$

$$n(\ce{C6H12O6}) = 2.47\ \mathrm{mol}$$

$$n(\ce{O2})= 6\times2.47\ \mathrm{mol} = 14.82\ \mathrm{mol}$$

$$V =\ ?$$

By the ideal gas law:

$$V= n\times24.45\ \mathrm{l/mol}$$

$$= 14.82\ \mathrm{mol} \times 24.45\ \mathrm{l/mol}$$

$$= 362.349\ \mathrm l \neq 1\,724\ \mathrm l$$

Tried using $pV=nRT$

$$V= 14.82\ \mathrm{mol} \times 8.314\ \mathrm{J\ mol^{-1}\ K^{-1}} \times 293\ \mathrm K / 760\ \mathrm{mmHg}$$

$$= 47.5\ \mathrm l \neq 1\,724\ \mathrm l $$

I don't know how to implicate the fact that the atmosphere is composed of $21\,\%$ of $\ce{O2}$ and $79\,\%$ of $\ce{N2}$. Any ideas?


texts:
I would like to know if there is a simple function that gives the current as a function of time in a concentration cell. The current is measured in the wire connecting the two terminals of the cell. The two half cells are isolated i.e. not connected by a salt bridge and the electrolyte is a liquid.

I am looking at a very simple case without involving the factors that affect the current and the internal resistance of the cell.

From my workings, I've got $\displaystyle I=C\ln\left( \frac { A-q }{ B+q }  \right) $ or more specifically

$\displaystyle \frac { dq }{ dt } =\frac { RT }{ nrF }\ln\left( \frac { VnF{ C }_\pu{ cathode }-q }{ VnF{ C }_\pu{ anode }+q }  \right) $

where $R$ represents the gas constant

$T$ represents the absolute temperature

$n$ represents the number of moles of electrons exchanged

$r$ represents the resistance of the wire

$F$ represents the Faraday's constant

$V$ represents the Volume of the solution (assuming both electrolytes' to be same)

$C$ represents the initial concentration of the electrolyte in each half cell.

Now I've tried integrating this function using WolframAlpha and then differentiating it to obtain the current explicitly as a function of time. Seems this function is too complicated for Wolfram to evaluate.(I've used the expressions with A,B,C)

Is my derived expression correct?

Also, shouldn't a simple dynamic process have a simpler equation?

Thanks.


texts: I have the following reactions from a book, but it is not explained how the different substances come into being. I don't know what happens to $\ce{3H2O (H3O)}$ in the second line.


texts: How can we directly add half cell potentials to measure the EMF of a galvanic cell?

texts:
We know that $E^\circ_{\text{cell}}=E^\circ_{\text{reduction at cathode}}+E^\circ_{\text{oxidation at anode}}$. For example, in a cell $\ce{Zn(s) | Zn^2+(aq) || Cu^2+(aq) | Cu(s)}$, $$E^\circ_{\text{cell}}=E^\circ_{\text{reduction at cathode}}+E^\circ_{\text{oxidation at anode}}=E^\circ_{\ce{Cu^2+/Cu}}+E^\circ_{\ce{Zn/Zn^2+}}$$

This makes sense to me. I think of $E^\circ_{\text{cell}}$ as the $E^\circ$ value of the net cell reaction i.e. of $\ce{Zn(s) + Cu^2+(aq) -> Zn^2+(aq) + Cu(s)}$.

But, consider this cell: $\ce{Zn(s) | Zn^2+(aq) || Ag^+(aq) | Ag(s)}$ According to my textbook, the $E^\circ_{\text{cell}}$ value here is again defined by:

$$E^\circ_{\text{cell}}=E^\circ_{\text{reduction at cathode}}+E^\circ_{\text{oxidation at anode}}=E^\circ_{\ce{Ag+/Ag}}+E^\circ_{\ce{Zn/Zn^2+}}$$

But, I think this is not correct.
Consider the fact that this cell is made up of two half cell reactions:

$$
\begin{array}{}
\text{Oxidation}&\ce{Zn(s)}&\ce{-> Zn^2+(aq) + 2e-}&E_1^\circ\\
\text{Reduction}&\ce{Ag^+(aq) + e-}&\ce{-> Ag(s)}&E_2^\circ\\
\text{Net cell reaction}&\ce{Zn(s) + 2Ag^+(aq)}&\ce{-> Zn^2+(aq) + 2Ag(s)}&E_3^\circ\\
\end{array}
$$

and that we can't add $E^\circ$ values directly, since they are an intensive property. Instead, we need to say that $\Delta G_3=\Delta G_1+\Delta G_2$ and then write $2E_3^\circ=2E_1^\circ+E_2^\circ$ or $E_3^\circ=\frac{2E_1^\circ+E_2^\circ}2$, which is definitely $\neq E_1^\circ+E_2^\circ$, as my textbook says.

I believe I have correctly presented everything here, and cannot figure out my mistake. Where am I wrong?


texts: Are metallic/ionic bonds weaker than covalent bonds?

texts:
In mineralogy class, I was taught that metallic and ionic bonds are weaker than covalent bonds and that's why quartz and diamond have such a high hardness value. However, in organic chemistry class, I learned that covalent bonds are weaker than metallic and ionic bonds, thus organic substances have a much lower melting point than that of metals and ionic compounds.

What am I getting wrong? Are ionic and metallic bonds weaker than covalent bonds or not?


texts:
I'm interested in learning organic chemistry, and am following a text (Organic Chemistry by Clayden) and an online course. I also have access to ChemBio3D.

I feel as though the way chemistry is taught conventionally is more difficult than it needs to be. Some online courses utilize industry software when teaching things (such as using MatLab in engineering), which makes visualizing and understanding a lot of the theories and concepts taught in books much more intuitive, since you can replicate the theory directly into a program.

Does a similar course exist somewhere for chemistry? I'm not talking about the little java applets that are available everywhere that mimic certain reactions or visualize concepts, I mean a course that utilizes a powerful software suite such as ChemBio in order to teach organic chemistry? Something that will teach both organic chemistry at a proper undergrad level and a good piece of industry software at the same time?


texts: I'm taking chem classes, and am interested in learning a some biochem on the side, on my own. I've bee looking for a decent book, though I'm on a bit of a tight budget so not brand shiny new ones upwards of a hundred. Hopefully. Obviously I don't want something ancient just for reduced price, so two questions. How many years back is ok to use as a cutoff for publication date, and any suggestions?


texts: Formation of oximes by ketones and aldehydes

texts: Why do symmetric ketones form a single oxime and asymmetric aldehydes and ketones can form two isomeric oximes?


texts: Can sodium (just sodium, not with liquid ammonia) react with terminal alkynes in a simple acid-base reaction to form sodium alkynide and dihydrogen (just as it reacts with $\ce{H2O}$ to form sodium hydroxide and $\ce{H2}$)?


texts: Reducible representations - choice of new basis

texts:
I was looking at this tutorial about reductions of representations. At first, the basis consists of four orbitals $(s_N, s_1, s_2, s_3)$ and the representations look like this

and we want to reduce the 3D $\Gamma^{(3)}(g)$ representation. Because its matrices aren't block-diagonal, we need to perform some similarity transform to get them into the convenient form. For that, we should choose a new appropriate basis, i.e. the linear combination of our orbitals.

Now the tutorial says that the appropriate new basis looks like this:

And yes, the basis is correct and the new block-diagonal matrices can be further derived using it.

But I have no idea, how did the author come with this specific basis.

So, how can I find the appropriated basis to reduce a reducible representation?


texts: Bomb calorimeter and heat capacity of calorimeter

texts:
Can anyone describe the process through which we determine the heat capacity of calorimeter, for me?

The formula is
$q_{calorimeter} = C_{calorimeter} \times \Delta T$

The heat of bomb calorimeter is shown to be  the same as  negative heat of reaction. But without mass, their unit would be different, no?


texts: Calculating Molar Volume from crystal volume

texts:
I am trying to calculate molar volume of certain crystal lattices to be used for crystal growth kinetics calculations. The information I have is the crystal volume & crystal lattices. For example the crystal $\ce{Cu41Sn11}$ has the structure cF416 and the information taken from a certain crystal database is as follows:

Atom Formula: Cu41.5Sn10.5

Cell volume:    5.81258 nm3

Cell density (calculated):  8.85 Mg m-3

Now I have tried 2 approaches to it.

First was the wikipedia formula for molar volumes

Vm= NAVcell / Z

molar volume = (Avorgados number x crystal cell volume) / number of formula units in a crystal

This gives the following output for the above mentioned crystal

Molar Volume = 6.022 x 1023 x 5.81258 x 10 -27 / 51

Molar volume = 6.731 x 10 -5

The second one is i figured out the formula

Molar volume = Molar Mass of crystal / Cell Density

So in this case:

Molar mass of crystal $\ce{Cu41Sn11}$ = 41 x 63.546 + 11 x 118.71 = 3911.2 gms (3.9112 Kg)

Molar Volume = 3.9112 / 8850 = 4.41944 x 10 -4

These two approaches yield two different results, so i wanted to make sure where am i making the mistake?

In case you're interested in the crystal database, here it is:


texts: In the benzenediazonium $\ce{C6H5N2+}$ the nitrogen contributes its lone pair to the carbon in benzene. So where is one electron of that carbon, since it is not used for bonding with nitrogen where has one of the electron of carbon gone?


texts: structure information form IR and Raman spectra?

texts: Is it possible to gain the idea of full molecular structure from IR or Raman spectroscopy?


texts:
I have got the homework to balance the following redox reaction.

$\ce{Cr(OH)3- + HO2- -> Cr2O7^{-2} + OH- }$(Basic medium)

To balance this reaction first thing we need to do is to find the oxidation number of each element.

My efforts:

I have found out oxidation number of each element on product side.. But it is bit confusing in reactant side.

Can any help me in finding the oxidation number of elements on reactant side ?


texts: Why do carbonyl groups lower antibonding orbital energies of conjugated systems?

texts:
In the chapter on conjugation in Organic Chemistry by Clayden, Greeves, Warren and Wothers, there's a brief discussion of pigments with conjugated systems that includes the following paragraph (first edition, p. 171; emphasis mine):

  Transitions from bonding to antibonding π orbitals are called π → π* transitions. A much smaller energy gap is available if we use electrons in a nonbonding orbital as the electrons start off much higher in energy and can be promoted to low-lying antibonding π orbitals. We call these transitions n → π*, where the ‘n’ stands for nonbonding. It is easy to find coloured compounds throughout the whole range of wavelengths by this means. The colour of blue jeans comes from the pigment indigo. The two nitrogen atoms provide the lone pairs that can be excited into the π* orbitals of the rest of the molecule. These are low in energy because of the two carbonyl groups. Yellow light is absorbed by this pigment and indigo-blue light transmitted.

The bolded statement is not elaborated on or, as far as I can tell, addressed directly in the rest of the text. I took "these" to mean "π* orbitals" rather than "lone pairs"; my best attempt at deducing an explanation is something like this:

  The bonding orbitals in the carbonyl group are polarized towards the O atom, exposing a positive charge on C and shifting electron density in the π* orbitals toward C. These two effects combined mean that any electrons in π* experience a strong attraction to the carbonyl group, lowering the overall energy in π*.

Is this roughly correct?


texts: To what state would copper wiring revert if abandoned for centuries?

texts:
Would copper wires from power transmission or telephone lines acquire a patina but remain largely intact, or oxidize into dust after a century or more without replacement or maintenance?

Obviously environmental factors would be enormous; ideally I'd like to know what the metal's state would be in ideal (underground?), typical (temperate zone), and worst-case (near salt water?) scenarios. Clearly some circumstances allow copper objects to survive largely intact for several thousand years, since such artifacts have been found by archeologists, but does this require very exceptional circumstances?

This question is inspired by an answer on the Worldbuilding site, which claims that a post-apocalyptic society would have a difficult time developing metallurgy as the rusted remains of human civilization would be more difficult to smelt than the naturally-occurring ores which were relatively abundant during the Stone Age. Hopefully by asking about this copper wires specifically, I have an appropriate question for this site. If so, I may ask another question about iron and steel.

I did not have much luck in finding relevant tags. Any assistance there is appreciated!


texts: Can you combine elemental gold and boron?

texts:
Is it possible to combine gold and boron to form compounds? A simple example being:

$$
\ce{Au + B -> AuB}
$$


texts: How to delete everything but a specific ligand from a PDB file using Linux-compatible free software?

texts:
I would like to delete everything from a PDB file except a specific ligand that I know the PDB code for. Is there a simple way to using free Linux-compatible software? If you want a specific example for your answer 1YAT and its ligand FK5 (tacrolimus) is an example I'm presently working on. I think PyMOL might have this capability using the delete command but running:

delete /1YAT/A

which should delete the macromolecule (chain A) at least but I saw no visually-obvious change. I have viewed the PyMOL Wiki article on the delete command but it was not helpful as what name meant was not obvious to me.

By free software I mean free of charge not free as in freedom. One piece of software that I used to do this with on Windows was Accelrys (or BIOVIA) Discovery Studio Visualizer, tried to run it on Arch Linux, however, as it has a Linux binary, but it failed to run. This is presumably because it is for Red Hat Enterprise Linux/SUSE Linux Enterprise which has too old of system libraries for Arch Linux compatibility.


texts: Which electrons will be taken when oxidations take place and how does the resulting orbital diagram look like?

texts:
In detail, what I really mean is which electron in which orbital is being taken when a oxidation happen? Let me give a example: chromate ion(II)

Two electrons are taken but from which orbital:


texts: Type of chirality in polycyclic compounds

texts:
Ignoring whether or not this molecule could exist, is there a name for this type of chirality? This molecule's mirror image cannot be superimposed on itself but there are no chiral centres.

Even though the bottom boron only has three substituents, the fact that they are all joined at the top gives it similar geometrical properties as if it were tetrahedral.
The InchI is InChI=1S/C4H8B2OS/c1-2-6-7-3-5(1)4-8-6/h1-4H2


texts: Why are beta-ketoacids better at decarboxylation than gamma or delta?

texts:
My book claims that beta-ketoacids and beta-dicarboxylic acids are better at decarboxylating than their gamma and delta counterparts. Why is that?

I would assume that since gamma and delta keto-acids make a larger ring intermediate (less ring strain) and thus the energy barrier for reaching that intermediate would be lower...


texts:
When I was perusing the works of Schwarz on atomic structure, I came across the unfamiliar term of d-orbital collapse.

He describes it as a variation in energetic sequence from group 1 to 3 elements such that the order changes from 4s<4p<3d in K, 4s<3d<4p in Ca and 3d<4s<4p for Sc and subsequent elements.
He continues to say "It is the result of the interplay of nuclear attraction, of imperfect shielding by the inner-core electrons, and of angular-momentum dependent centrifugal forces. It explains why 4s becomes occupied in K and Ca before 3d, but 3d before 4s in the transition elements."

He states the orbital energies ε are represented by the effective quantum numbers neff = 1/(√|ε|/13.606 eV)^3. This seems to imply the orbital energy of 4s is lower than 3d for K and Ca hence the 4s orbitals are occupied in preference to 3d in their atoms.

This contradicts various literature which state according to Hartree-Fock calculations the 4s orbital never has a lower energy than 3d, regardless of which atom is being considered. ("Transition Metals and the Aufbau Principle" VPD, J. Chem. Educ. 1994 71 (6), 469; "Why Is the 4s Orbital Filled before the 3d" MS, J. Chem. Educ. 74: 498–503, 1996; "4s is always above 3d! Or, how to tell the orbitals from the wavefunctions" Pilar, J. Chem. Educ. 1978 55 (1), 2; "Transition metal configurations and limitations of the orbital approximation" Scerri, J. Chem. Educ. 1989 66 (6), 481)

Criticisms of a similar graph used in textbooks is that it features out-dated calculations made by R. Latter in the 1950s that seemed to indicate the energy of the 4s orbital was lower than that of 3d. The graph which shows the crossing-over of the energies of the 4s and 3d orbital energies, "is now known to be erroneous". ("A Critique of Atkins' Periodic Kingdom and Some Writings on Electronic Structure" Scerri, Foundations of Chemistry 1: 297–305, 1999) Schwarz also alludes to this in his article: "The graphic is quantitatively correct, in contrast to qualitatively incorrect artwork in many chemical and physico-chemical textbooks.", yet his graph reproduces the same phenomenon.

Does Schwarz's d-orbital collapse actually imply 4s orbitals having lower energy than 3d? Is there any way to renconcile the contrasting information presented?


texts: Can compounds (or only elements) be referred to as oxidising and reducing agents?

texts:
In the reaction

$$\ce{3CuO (s) + 2NH3 (aq) <=> N2(g) + 3H2O(l) + 3Cu(s)}$$

the oxidation number of $\ce{Cu}$ goes from $+2$ in the reactant side to $0$ in the products, and so it is reduced.
The oxidation number of $\ce{O}$ is $-2$ and stays the same on both sides.

My textbook refers to $\ce{CuO}$ as the oxidising agent. Is this because the $\ce{Cu}$ in $\ce{CuO}$ is oxidised while $\ce{O}$ is neither oxidised or reduced, so overall it is an oxidising agent?

What happens for a compound $\ce{AB}$ where $\ce{A}$ gets oxidised and $\ce{B}$ gets reduced? Do I call the compound $\ce{AB}$ a reducing agent if the net change in oxidation number (between the two elements $\ce{A}$ and $\ce{B}$) is negative?


texts: Electrolysis of a calcium salt in polar aprotic solvent

texts: If i found a calcium salt that is soluble in acetone or ethyl acetate, which are polar aprotic solvents, and attempted electrolysis, what would happen? Since polar aprotic solvents are used in metal-air batteries I don't think there would be a reaction between the newly formed metal and solvent. At the same time, no one uses such method industrially. Maybe it's just inefficient, or maybe it doesn't work?


texts: How does one measure the change in enthalpy of hydration?

texts:
I am learning about lattice enthalpies, and my textbook talks about determining the lattice enthalpy from the standard change of enthalpy of solution and the change of enthalpy of hydration of the ions. It says that the changes in enthalpy of solution and hydration can be determined experimentally but that the lattice enthalpy cannot be.

However, I am struggling to think of how one can measure the enthalpy change when one mole of gaseous ions is dissolved in water under standard conditions. I thought one would encounter the same problem as with the lattice enthalpy, and this involves one mole of an ionic lattice being formed from its gaseous ions under standard condition.

I thought that the problem with this was getting the exact amounts of gaseous ions under standard conditions.


texts: Why are sp hybridized carbocations high energy?

texts:
You don’t see carbocations on double bonds very much, and here's a good reason: compared to sp3, there is more s character in the orbitals, so the empty orbital is held more closely to the nucleus. This is destabilizing if we’re talking about positive charge.

(source)

This doesn't really make sense. Positive charge arises from the lack of electrons. How does holding an empty orbital (regardless of whether that makes any physical sense) closer affect your stability if the empty orbital is ... empty?

So, what is the exact reason sp2 (aren't most carbocations sp2 though?) and sp carbocations are generally less stable than their sp3 counterparts?

Also, how can we have an sp3 carbocation? Huh?!

The only reason I can think of is that it's energetically expensive to make an sp carbocation ... pulling electrons which are held more tightly to the nucleus away is probably harder than pulling away electrons which are not as close to the nucleus.

I can't think of any reason why the end products would be any less/more stable ... if anything an sp carbocation should be more stable than an sp2 carbocation in that in the sp carbocation the electrons are held closer to the nucleus and therefore better stabilizing the nucleus.


texts: When naming an organic molecule - which group has the highest priority: methyl or methylidene?

texts:
I have been tasked with naming Myrcene. (see image below)

Which of the following names is correct?

7-methyl-3-methylidene-oct-1,6-diene

or

3-methylidene-7-methyl-oct-1,6-diene

Thank you in advance :)


texts: Transforming a cis double-bond to a trans double-bond using any mechanisms of my choice

texts:
For my final, I need to be able to a trans-double bond from a cis double bond. Here is what I drew:

I essentially created a triple bond and oxidized


texts: What is the chemical composition of Turnbull's blue?

texts:
I was studying qualitative analysis from this book and  I found some tests for testing the presence of the cation $\ce{Fe^{++}}$.

There was a test in which we add $\ce{K4[Fe(CN)6]}$ solution to a solution of a ferrous salt which results in the Turnbull blue precipitate. Now according to Wikipedia, the Turnbull blue and Prussian blue are the same compound, ie, ferriferrocyanide $\left(\ce{Fe4[Fe(CN)6]3} \right)$.

But the book says that Turnbull blue is ferroferricyanide $\left(\ce{Fe3[Fe(CN)6]2}\right)$ which kinda makes sense because we are adding ferricyanide to ferrous solution.

I am preparing for an exam in which such questions can be asked SO I just want to settle this once and for all, which is wrong, Wikipedia or the book?


texts: What is the correct way to draw the end groups of polylactic acid?

texts:
I came across two different ways to draw the end groups of polylactic acid:

 (source)

AND:

 (source)

Which one is the correct way?


texts: Hydrolysing a compound by repeated methyl and hydride shifts

texts:
The question is to predict the major product in the following reaction.

First of all the proton will abstract the bromide ion resulting in the formation of a primary carbocation which being unstable would rearrange.I have the following idea about how the reaction should proceed.

However I have doubts if such repeated methyl and hydride shifts are actually possible.Is the same product possible through a different energetically favourable mechanism?Thanks.


texts:
The usual explanation for the molecular dipole moment of $\ce{NF3}$ being smaller than that of $\ce{NH3}$, despite the $\ce{N-F}$ dipole being stronger than the $\ce{N-H}$ dipole, is that influence of the lone electron pair on nitrogen is to oppose the net $\ce{N-F3}$ dipole, while enhancing that of $\ce{N-H3}$. See, for example, this good example.

What bothers me about this explanation is that when the $\ce{N-F}$ dipole is calculated (experimentally, I think), the effect of the electron pair on $\ce{N}$ is already factored in. Likewise for the calculation for $\ce{N-H}$.

Putting the question in terms of the language of the linked article:

  [T]he lone pair's negative concentration will augment the polarity contribution from the polar bonds while for the $\ce{NF3}$, the lone pair's dipole would subtract from the dipole contributed by the NF bonds.

If the lone pair on $\ce{N}$ subtracts from the $\ce{N-F}$ bond in the molecule it must have had the same effect in the original diatomic dipole calculation. Likewise for $\ce{N-H}$.

If this is true, assuming identical $\ce{N-F}$ and $\ce{N-H}$ bond angles in $\ce{NF3}$ and $\ce{NH3}$, it seems that the vector calculation should still give a stronger dipole moment for $\ce{NF3}$. [Please regard this as a question!]

One thing that would lessen the molecular $\ce{NF3}$ dipole moment is a smaller $\ce{NF}$ bond angle (compared to $\ce{NH}$), which increases the lateral component of the dipole at the expense of the axial, making the (axial) resultant smaller. I think fluorine is larger than hydrogen and maybe this would tend to push the fluorine atoms out laterally, decreasing the resultant axial dipole. However I do not see this as an explanation in texts so I am guessing it is wrong.

My confusion is that the vector algebra doesn't seem to support the argument but there is probably something I am not taking into consideration.


texts: What is created when "Iron-Out®" is mixed with household bleach?

texts: I accidentally mixed bleach in a toilet bowl that had Iron-Out in it. The gas almost overwhelmed me, and left me gasping for breath for a good 15 minutes. What in the heck did I create with those two chemicals?


texts: A solvent is an element which dissolves something, basically the solute. Normally, all the solvents we encounter are in liquid phase. So, I was wondering if there could be any solvent in a gaseous phase. Can there be any gaseous solvent, after all?


texts: How to compute Franck-Condon Factors for spin-orbit states?

texts:
I am computing Franck-Condon Factors between the neutral ground state and cationic states to simulate the photoelectron spectra (using Gaussian 16, freq=FCHT). The target cationic state is a pi state and has 3/2 and 1/2 spin-orbit components. I have done optimization and frequency calculation for the pi state in TDDFT. Thus I have FCF for the pi state before spin-orbit splitting. How do I compute FCF two spin-orbit components ? In another word, how can one optimize the two different components of a spin-orbit state. I used the same FCFs for both the components separated by the SOC. It provided reasonable agreement with experiment, however, I wonder if there is more accurate way of doing it.
Thank you for your help.


texts: Can someone explain the differences in decomposition rates for when two molecules which have 2 different substituents?

texts: Just having trouble on why these two have such different decomposition rates, I would like to think its because NO2 is electron withdrawing but I cannot see why this would change the rate...some please explain?


texts: Why triiodide ion does not form ionic bond with cation having +2 charge?

texts:
In general, I found that triiodide ion generally forms ionic bond with cations having +1 charge like  $\ce{NH4+I3-}$, $\ce{K+I3-}$, $\ce{Tl+I3-}$. But, I have never seen triiodide ion forming ionic bond with cations having +2 or +3 charge like  $\ce{Ba^2+(I3^{-})2}$, $\ce{Pb^2+(I3^{-})2}$, $\ce{Bi^3+(I3^{-})3}$. If properly written, it would  look like $\ce{Ba(I3)2}$, $\ce{Pb(I3)2}$, $\ce{Bi(I3)3}$. These compound has never existed and would not likely to exist. But what is the reason behind this?

Recently I went through this question:-

  Why isn't thallium triiodide stable?

One of the  commenter  said:-

  Thallium Tri-Iodide $\ce{Tl+(I3)-}$ does exist.  Thallium (III) Iodide, $\ce{Tl^3+(I^{-})3}$ to my knowledge, does not.

I was quite surprised at first seeing that $\ce{TlI3}$ exist because I knew that due to inert pair effect, thallium will form Thallium(I) compounds like $\ce{TlCl}$, $\ce{TlBr}$,  $\ce{TlI}$ etc. but I  realized that the compound contains  $\ce{Tl+}$ and not $\ce{Tl^3+}$. But what about the corresponding $\ce{Pb^2+}$ and $\ce{Bi^3+}$ ions? Why does not they form triiodide compounds?


texts:
I know that in a compound, when there are two double/triple bonds its like :

1,3-diene ; 1,3-diyne and so on.

For three :

1,3,5-triene ; 1,3,5-triyne and so on.

But what about 4?

While doing a question I encountered this :

2,4,6,8-(What?)ene

Is it quad,quart,quater(like quaternary carbon) or something else?

Also, it would be helpful if you could extend it to like 5 or as much as you can double/triple bonds.


texts: Are imine or amine bonds similar to ethereal bonds, from the perspective of an enzyme?

texts:
I'm interested in enzymes that can cleave (hydrolyse or however) an ethereal bond ($\ce{C-O-C}$). Enzymes can evolve to act on chemicals/bonds that are similar to what they previously acted on, so enzymes with similar functions are also interesting.

I've been told by a couple of chemists that carbon-nitrogen-carbon bonds are similar to ethereal, so I was wondering if, and in what way that is true. Are the bonds in an imine group ($\ce{C-N=C}$) or a amine group ($\ce{C-NH-C}$), more similar to those in an ethereal group compared to a $\ce{C-C}$ pair, for example?

I guess from the perspective of an enzyme, if you were approaching the imine from the direction of the lone pair, that would feel pretty similar to an oxygen maybe?


texts: Why does tetrachloromethane have a higher boiling point than trichloromethane?

texts:
London dispersion forces (LDF) are present in all molecules, whether polar or non-polar. Molecules also exhibiting dipole-dipole interactions (in addition to the LDF) must have stronger forces of attraction than those molecules which exhibit only LDF.

Then, why does tetrachloromethane (carbon tetrachloride), which is a non-polar molecule exhibiting only London dispersion forces, have a higher boiling point ($\pu{77 ^\circ C}$) than trichloromethane (chloroform) ($\pu{61 ^\circ C}$) which is a polar molecule, exhibiting dipole-dipole interactions?


texts: Why are isotopically pure diamonds 50% more thermally conductive than other diamonds?

texts:
A laboratory grown type-IIa diamond (no nitrogen defects) has a lambda of $\pu{1800-2200 W/mK}$, but an isotopically pure diamond of $\ce{^{12}C}$ can have up to $\pu{3320 W/mK}$.

Why are $\ce{^{12}C}$ diamonds so much more thermally conductive than diamonds with $\approx \pu{1.1\%}$ $\ce{^{13}C}$ atoms?

Sourcing for my question:
https://www.sciencedirect.com/science/article/pii/092596359290197V?via%3Dihub
https://adsabs.harvard.edu/abs/1990PhRvB..42.1104A


texts: Is the electric conductivity of chlorine ions influenced by its oxidation state?

texts:
I'm a high school student researching the conductivity of electrolyte solutions. In this excerpt of the CRC Handbook, I noticed that different ions containing chlorine have different limiting molar conductivity, and there seems to be a trend between molar conductivity and the oxidation state of chlorine:

Ion
Oxidation state of chlorine
$\Lambda$ in $\pu{e-4 m2 S mol-1}$

$\ce{ClO2-}$
+3
52

$\ce{ClO3-}$
+5
64.6

$\ce{ClO4-}$
+7
67.3

Does the trend really exist? If so, why did it happen? I found previous researches on the conductivity of $\ce{Fe^2+}$ and $\ce{Fe^3+}$, and the difference seemed to be a result of electrons spinning.


texts: During the 19th century many scientists did not believe in Dalton's theory of atoms. What was the alternative view of matter?


texts: Will Avogadro's number change if definition of atomic mass unit is changed?

texts:
I know that the relation between atomic mass unit and Avogadro's number is a reciprocal relation.
My question is if the definition of atomic mass unit is changed, suppose instead of 1/12th mass of carbon-12 isotope, we consider 1/24th mass of carbon-12 isotope, will the Avogadro's number change?
And if Avogadro's number changes will that change the mass of a mole of atoms of any element?


texts: Trifluoroacetic acid, Formic acid and dichloromethane

texts:
I am working in a small lab (in a small company) with very poor conditions, which I have to improve (for example: no sink , I have to wash the glassware in the bathroom). My organic chemistry is very poor, I am new to using solvents, and I have several basic doubts:

How to correctly wash the glassware after use?
How to correctly dispose of wasted solvents?
Should I leave the chemical fume hood on after using it and, if so, for how long?

I basically only do electrospinning here, using the respective solvents:
- Trifluoroacetic acid
- Dichloromethane
- Formic acid


texts: Uncertainty Principle in the Ground State of a Rigid Rotor

texts:
This is a fairly basic question which has bothered me for some time and I haven't been able to satisfactorily resolve.

In the ground state of the rigid rotor the energy is zero. That is, there is no zero point energy for this system. This means we definitely need to make sure we aren't violating the uncertainty principle for position and momentum.

So, the first place to look at is the wavefunction of the ground state. The wavefunction of the rigid rotor are the associated Legendre polynomials, and for the ground state (ignoring normalization) this is:$$P_0^0(x)=1.$$The point being, this is just a constant.

So, my first intuition is to say that we aren't violating position-momentum uncertainty because the wavefunction is only a constant so we know nothing about its location. This, however, I think is wrong because we solve this in spherical coordinates and the angle $\phi$ is constrained to be within $[0,2\pi]$. That is, our particle is somewhere on a sphere. Thus, this explanation doesn't work because the particle is somewhere on the sphere so we have some certainty of its position.

My next thought was that the uncertainty principle I'm thinking of is written as follows:$$\Delta p_x\Delta x \ge \frac{\hbar}{2}$$This, however, is wrong because it means that when the ground state energy is zero, the angular momentum is zero (that is, this is a closed spherically symmetric wave).

Thus, the next explanation I thought is that if I solved this in Cartesian coordinates rather than spherical coordinates, I would still get the same answer that the ground state energy is zero, but the x, y, and z position and x, y, and z momenta would all have positive, finite values which do not violate the uncertainty principle.

So, hopefully I've convinced you that this requires a slightly more nuanced answer than one might expect.

Is the last explanation correct in that when solving this in spherical coordinates, we should actually think about some other uncertainty principle than the one depending on Cartesian coordinates written above? Something like $$\Delta L \Delta r \ge \frac{\hbar}{2}$$

So, let me know if my reasoning has gone astray and where the solution lies. I feel a bit embarrassed that this isn't obvious, but I think my last point is where the answer lies.

Specifically, I'd like to see if anyone can address the question of the uncertainty principle in the ground state when this problem is solved in Cartesian Coordinates.


texts: Hexanoic acid and copper/brass - toxicity?

texts:
We have a sensor made of brass through which we are flowing organic solvent vapours mixed with air, typically hexane and various alcohols. After a year or so the interior is covered in a greenish-black slime. The smell is definitely that of hexanoic acid, so I am assuming much of the deposit will be the copper salts of the various acids.

Is there likely to be any significant toxicity with the probable compounds that may require special cleaning procedures?


texts: How can I balance the redox reaction of sulfur dioxide with oxygen?

texts:
How do I balance this reaction using half-redox equations?
$$\ce{2SO2 + O2->2SO3}$$

My work is:

Oxidation: $\ce{SO2 + H2O -> SO3 + 2e- + 2H+}$

Reduction: $\ce{H2O + 2e- + O2 -> SO3 + 2H+}$

Total: $\ce{SO2 + 2H2O + O2 -> 2SO3 + 4H+}$

BUT it's false. What did I do wrong?


texts: Why do we use the word phase and state of matter so interchangeably?

texts: I would be happy if someone explains me why the word "phase" and "state of matter" is used so interchangeably.Lets say we have HBr and another compound in the system both gases.Then am I to take two phases on a single phase when I plug in the Gibbs formula in Phase rule?


texts: Can Aluminum Hydroxide (Al(OH)3) be heated to it's melting temperature before decomposing?

texts: On the wikipedia page for aluminum hydroxide the listed melting point is 300 °C (572 °F), but in the same page it states that aluminum hydroxide decomposes at only 180 °C (356 °F). Can aluminum hydroxide be melted without decomposing?


texts: Aurora borealis - less favored energy transitions higher in atmosphere?

texts:
This question describes how some energy transitions become more prominent as you higher in the atmosphere. Short summary: Some electron transitions are "forbidden" by quantum mechanical selection rules, and so have a larger time delay from time of excitation until time of photon emission. Thus, low in the atmosphere (high pressure), it's more likely that the species loses the excitation energy by collision than emission.

However, as you go higher in the atmosphere, you see red (due to energy transition in atomic oxygen). The characteristic green line (also due to atomic oxygen, but different transition) disappears.

Why don't you see a mix of the two colours? After all, from the collision rate argument you would expect fast transitions (like the green of atomic oxygen) to become even more prominent.

Why is it that some transitions are less likely as you increase in height?

(I have a feeling that the answer to this question will also explain why nitrogen does not play a more central role in the colour of the aurora.)


texts: Does water acidity affect sugar solubility?

texts: For example, when making lemonade: will mixing sugar in water after adding lemon juice lead to a slower sugar dissolving rate, than if sugar were mixed in before adding lemon juice?


texts: Effect of Catalysis on Reaction Rate in elementary Reaction

texts:
I understand that there are many different catalytic mechanisms that suggest different ways of accounting for the effect of a catalyst on reaction rate. My question is:

Given a termolecular elementary (it is known it is an elementary reaction) reaction of the form:
$$\ce{A + B + C <=> D + E + C}$$
Does the rate of reaction simplify down (according to collision theory) to:
$$r = [\ce{C}]\bigr(k_\mathrm{fwd}[\ce{A}][\ce{B}] - k_\mathrm{rev}[\ce{D}][\ce{E}]\bigr)$$

Edit: To clarify my question, I have a gas phase elementary reaction of the form:
$$\ce{A + B + C -> D + E + C}$$
I have another of the form:
$$\ce{D + E + C -> A + B + C}$$
Whether they are exactly the same mechanism is irrelevant. My question relates to how quantitatively does a collision partner's concentration in a gas mixture affect reaction rate. i.e. is forward rate defined by (assuming that I know the reaction acts as an elementary reaction in that there is no intermediate):
$$r_\mathrm{fwd} = k_\mathrm{fwd}[\ce{A}][\ce{B}][\ce{C}]$$
and reverse rate defined by (reverse is also elementary reaction - not concerned if same mechanism just also acts in the rate law as a single collision event):
$$r_\mathrm{rev} = k_\mathrm{rev}[\ce{D}][\ce{E}][\ce{C}]$$
Therefore, the total rate, not assuming they're the same reaction just two elementary reactions that go in opposite directions and we've called on forward and one reverse, the total rate forward, taking into account our other reaction, is:
$$r = r_\mathrm{fwd} - r_\mathrm{rev}$$
$$r = k_\mathrm{fwd}[\ce{A}][\ce{B}][\ce{C}] - k_\mathrm{rev}[\ce{D}][\ce{E}][\ce{C}]$$
$$r = [C]\left(k_\mathrm{fwd}[\ce{A}][\ce{B}] - k_\mathrm{rev}[\ce{D}][\ce{E}]\right)$$
Therefore quantitatively a collision partner does not change the overall rates direction but rather enhances it in both directions. Is this correct?


texts: Which formula can be used to calculate the exact hydronium concentration present in sodium hydrogen carbonate solution?

texts:
Which formula  can be used to calculate the exact  hydronium concentration present in  sodium hydrogen carbonate solution ?

$$\ce{[H3O+]}=\sqrt{K_\mathrm{a1}K_\mathrm{a2}}$$
$$[\ce{H3O+}]=\sqrt{\frac{K_\mathrm{a1}K_\mathrm{w}}{[\ce{NaHCO3}]}}$$
$$[\ce{H3O+}] = \sqrt{\frac{K_\mathrm{a1}K_\mathrm{a2}\times[\ce{NaHCO3}]+K_\mathrm{a1}K_\mathrm{w}}{[\ce{NaHCO3}]+K_\mathrm{a1}}}$$

I  tried to order the series  of reactions once sodium hydrogen carbonate  is dissociated according  the following sequence :

Taking into consideration  equation two and equation four, and  taking the assumption: Degree of ionization=degree of hydrolysis, an approximate calculation hydronium concentration can be done by the  formula  one.
Recognizing  equation four and equation two  , that for every one mole of carbonate- formed, one mole of hydronium was formed, and  for every mole of carbonic acid formed, one mole of hydronium  was used up and when comparing K value between both of these equation, I can ignore the contribution of equation four. And because of the low concentration of carbonic acid  in equation three and low carbonate ion  concentration in equation five , I can ignore the contribution of  both equation. So I take into my consideration equation two to derive formula two.
I tried to  derive formula three but  I don't know the assumptions beyond this formula and how to derive it.
I need to know how  to calculate concentrations  of  all species are present in  sodium hydrogen carbonate solution ?
I appreciate any help.


texts:
I was given an online assignment problem today. The answer was to be given to 2 decimal places. The answer I gave was $$P_2=0.06$$

This to me seems like 2 decimal places. However the answer was incorrect. I then wrote $$P_2=0.064$$

It was correct. I know I'm being knit-picky but I genuinely just want to know your thoughts on this.

Would you call this 3 decimal places and 2 significant figures, or 2 decimal places and 2 significant figures. In the context of the assignment it doesn't matter a whole lot but I still think he should have written 2 significant figures.

What's your 2 pence on the matter?


texts: How is serine ionized in serine proteases?

texts: I read that serine isn't strongly acidic so how is it that in serine proteases it is able to have its pKa lowered by the catalytic triad?


texts: What are the boiling points of DMSO-water concentrations?

texts: What are the boiling points of DMSO-water concentrations with respect to wt% DMSO? I have found extensive information on the freezing point change of wt% DMSO but nothing regarding boiling.


texts: Does the object blocking the cathode rays in Thomson's cathode Ray experiment need to be opaque?

texts:
Thomson kept an "opaque" object in the cathode ray tube and he saw the shadow of the object.then he decide that the cathode rays follow a rectilinear path. But Thomson also discovered that cathode rays actually consist of particles.

Suppose I keep a transparent object (such as a thick slab of glass) instead of the "opaque" object. If the cathode rays are particles, then we would still find a shadow formed behind the glass slab (the particles wouldn't be able to pass through the slab).

Numerous articles and books I've referred to insist that the experiment requires that an "opaque" object be placed inside the cathode ray tube.

However, in my example with the glass slab, "opacity" doesn't seem to be a pre-requisite for the successful implementation of the experiment. Am I right in thinking this?


texts: How to cheaply extract iodine from an alcoholic solution?

texts: I have an alcoholic solution of iodine. My goal is to extract the pure iodine without using rare or expensive compounds. How could I do this?


texts:
I soaked a large jar full of pebbles (from a river) in bleach water for a couple of years and the rocks came out super smooth and shiny when dried. I have tried to repeat this process again but am not having any luck with it this time. Have you ever heard of this and do you know if there is a certain ratio of water to bleach that works? Perhaps I put something else in the water the first time and caused a chemical reaction?

Here is a picture of the rocks that became smooth and shiny after a couple of years in water with bleach added for keeping the water clean and clear. And a picture of the rocks I have done the same to for a year. An interesting note is that fossils such as Petoskey Stones do not change at all.


texts: Why are double bonds shorter than single bonds?

texts:
We're told in chemistry class that the order of bond length is:
triple < double < single

Can anyone explain WHY this is the case? Is it because multiple bonds involve stronger attraction between the two atoms or something else?


texts: Why does malleability and ductility of interstitial carbides decrease?

texts:
Why does the malleability and ductility of interstitial carbides decrease? I read the following in my book, but I am not able to find what is the reason for the same. Why does this happen? Is it to do with the change in lattice properties?
I read this in JD Lee (adapted version by Sudarshan Guha), it stated after a section on interstitial carbides

The hardness and density are increased for these (interstitial) carbides while malleability and ductility are decreased.


texts: Elution Rate - Alkanes VS Alkenes in Gas Chromatography

texts:
Some references say that alkanes elute faster than alkenes, whereas in my textbook the higher volatility of alkenes means they elute faster than alkanes. This is for gas chromatography.

  Alkenes are more polar than alkanes due to more electron-withdrawing
  $\text{sp}^2$-hybrid orbitals (more s-character draws electrons closer to
  nucleus).

Can someone please clarify - bit confused.


texts: What are the correct resonance structures of bromoethene?

texts:
Can anyone explain why my textbook only gives the following resonance structures?

  Write the important resonance structures for each of the following:

I also put two resonance case where the double bond electrons are moved on the individual carbon atoms.


texts:
I would like to know what is the chemistry of cutting. For example, when we use a knife to cut through bread what exactly happens on a molecular level? Are ions formed, do long organic compounds (e.g. in cheese) break, or are just intermolecular interaction that seize to exist?

Thanks a lot in advance.


texts: How can I save an EEM file on a Fluoromax4?

texts:
I'm trying to run excitation-emission matrices on some water samples, but I'm running into some software issues that the manuals aren't helpful for. In order to use R studio to extract my data, I need to save my output as a .eem file, but I don't see how to do that.
When I try to save my matrix, the only option I get is an .spc, which it doesn't even let me do that - I get an error saying I need to change my matrix into a worksheet. I can't even figure out how to do that.
Is it saving these eems automatically somewhere I can't find? All I've been able to do is save an ASCII version of my data, which isn't a format the eemR package lets me import.
Hardware: Horiba Fluoromax 4
Software: Horiba FluorEscence, R studio eemR, Matlab drEEM
Thanks


texts: Why butane exist as a liquid in a lighter ?

texts:
This is my go at explaining after researching ...

Butane is light and normally would be a gas at standard atmospheric temperature and pressure due to Low boiling point (-1degrees)

The butane gas is in liquid state in the lighter . This is because , when it is placed in the body of the lighter , it is placed there under very high pressure as compared to the open air in standard atmospheric temperature and pressure .

Increasing the pressure of the butane gas forces the molecules closer together . This is because increase in pressure will also lead to increase in average kinetic energy meaning molecules need to 'hold' onto each other more to prevent themselves from breaking their bond. (LDF)
With that theory, that means increase in pressure leads to increase in boiling point of the molecules because more heat is needed to break the bonds and move apart .

Hence , When the butane gas are compressed at high pressures , (at a certain pressure for butane) , the alkane will undergo a phase change from gas to liquid.

Now , am I right to say that the vapour pressure is equal to the pressure of the butane gases in the small container , That's why they undergo a phase change immediately ?


texts: Is the pz orbital wave function three- or four-dimensional?

texts:
The wave function of the $2\mathrm{p}_z$ orbital is
$$Ψ = \frac{1}{4\sqrt{2π}}\left(\frac Z a\right)^{5/2} r \mathrm e^{-Zr/a}\cos θ.$$
I'm confused if this function will be a three-dimensional function or a four-dimensional function?
My professor told me that
$$z/r = \cos θ,$$
where $θ$ is the angle made by $r$ with the $z$ axis. So, I guess it will be four-dimensional since we would have to then plug in
$$r = \sqrt{x^2 + y^2 + z^2}$$
in the equation.
But when he plotted the function, he plotted a three-dimensional one! What is the correct answer and why?


texts: Why are tertiary carbocations so stable?

texts:
Today our lecturer provided this data to illustrate the relative stability of carbocations.

\begin{array}{|c|c|c|c|c|} \hline
\text{Substrate} & \ce{t-BuBr} & \ce{i-PrBr} & \ce{EtBr} & \text{MeBr}\\ \hline
\mathrm{Relative~rate~of~S_N1~reaction} & 1.2 \times 10^6 & 12 & 1 & 1\\ \hline
\end{array}

Additionally, in several places I have seen it said that tertiary carbocations are common and stable whereas secondary carbocations are only rarely stable and primary obviously not at all.

What is immediately obvious is that going from a primary to a secondary carbocation only produces a slight increase in rate, but the change from secondary to tertiary produces an enormous change. The number of bonds available to participate in hyperconjugation increases linearly along the series but the rate clearly doesn't so there must be some other factor at work. The only idea I had was that there might be some similar effect to Y-aromaticity taking place in the trigonal tertiary cation (there are six electrons involved in hyperconjugation after all) but I have no idea whether this is a plausible suggestion.


texts: Can magnetic fields affect a chemical reaction?

texts:
This question was asked recently in an interview and I just said that "Yeah, like if the reaction involves ions or paramagnetic species". But the interviewer went on and asked me to elaborate on HOW will the reaction change, and I was stumped.

So what I am asking here is what will happen if I allow a chemical reaction to take place in a live MRI machine?


texts: What product will be produced when a sucrose and potassium nitrate mix burns?

texts:
What product will be obtained get when a sucrose and potassium nitrate mix, which are the ingredients for smoke bomb, are burned in a combustion container?

$$\ce{KNO3 + C12H22O11 -> ?}$$


texts: Is the end of a cigarette on fire when lit?

texts: Is the end of a cigarette on fire when it is lit? Or is it smoldering? Is there a chemical difference between the two?


texts: How do sunscreens protect the skin from UV rays?

texts: I was unsure to the largest extent about whether I should post this question in chemistry Q & A or bio Q & A until I just read that sunscreens "absorb" UV rays, not allowing the most of those rays from penetrating into the skin. So when this is about the combination, it must be chemistry. Anyhow, is there any special name for these "absorbents"? And how exactly, do they "absorb" UVA & UVB? (I'm not really definite if this absorbing is really a scientific expression or not, and that's why I use quotations when using the word) I, myself, reckon that the sunscreen products form a special compound on the skin or they make the body produce something as a shield against UV rays, but I have got no clues.


texts: Why does CO2 only exist in gaseous and solid state under STP/SATP?

texts:
Why does carbon dioxide only exist in gas and solid state under STP/SATP conditions?

$\ce{CO2}$ pressurized to $\pu{5.1 atm}$ can exist in all 3 states: solid, gas, and liquid.

However, why couldn't the same happen in 1atm pressure? As a solid chunk of dry ice is the coldest you could get $\ce{CO2}$, why cant you warm it up slightly but still have it cold enough to turn into a liquid, instead of directly to a gas?


texts: Benzylation and acetylation of amines and alcohols

texts:
Question

Attempt
Since the nitrogen site is more nucleophilic it should react first. But still Oxygen can react and hence I believe A should be right. But the book says C. Where did I go wrong? Please help.


texts: Disproportionation of silver(I) in aqueous solution

texts:
Use the following equations to predict whether or not $\ce{Ag+}$ ions will disproportionate in solution:
$$
\begin{align}
\ce{Ag+(aq) + e- &-> Ag} &\qquad E^\circ = \pu{+0.80 V}\\
\ce{Ag^2+(aq) + e- &-> Ag+} &\qquad E^\circ = \pu{+2.00 V}
\end{align}
$$

I used the method $E_\mathrm{cell} = E_\mathrm{red} - E_\mathrm{ox}$ and thought that $\pu{0.80 V}$ would be more negative. Therefore, it is oxidised and the reaction would be thermodynamically feasible.
However, my textbook and another webpage has a different answer. I am a bit stuck on how to get the right answer. Please someone explain me.


texts: Are hydrogen atoms in acetone molecule acidic?

texts: My chemistry book says that acetone is aprotic, but I think that, since the conjugate base of acetone has possible  resonating structures, the hydrogen atom must be free to move out as $\ce{H+}$ (as the resulting structure is more stable than the previous one). Where am I going wrong?


texts:
I'm looking for a table showing which size of bar to use for a given volume to stir.
Or a formula if there is one.


texts: Which one is the stronger acid among these two compounds?

texts:
According to me, acidity for these two compounds depends primarily upon two factors:

inductive effect due to the ring
electronegativity of the atom bearing   the hydrogen atom

If  the  first factor predominates, second compound would be the most acidic otherwise the first compound would be the most acidic(as nitrogen bears a methyl group too).
So, which one is the most acidic?


texts: How to I neutralize the smell of (VERY) spoiled milk

texts:
Let's say I have a cup full of milk that had been at room temperature for months (apparently my son was running an experiment...). The smell started seeping out of the makeshift lid, and it's horrible. I have no background in chemistry but I imagine there might be a way to neutralize the smell before getting rid of the contents.
I'm worried if I just flush it down the pipes it might linger and make the whole house smell. Also, ideally I would like to salvage the cup because it's a very nice handmade glassware (he was running a fancy experiment).
Again, this has been there for months so I hope there isn't any dangerous bacteria still around, and any advice to get rid of the smell and clean the thing would be enormously appreciated.


texts: Activation of alcohols by forming sulphonate ester

texts:
In activation of alcohol by tosyl chloride, why does the chloride ion not displace the poor leaving group?

I think that's because chlorine is a poorer base than that thing which will be formed. But that should not be true considering delocalisation.

Additional Information:

I know this question is unclear because I don’t know the name of the things formed when alkyl group has left the sulphonate ester so please edit this.


texts: Acid-base titration: Unknown base in burette or flask?

texts: While finding the concentration of $\ce{NaOH}$ via titration with $\pu{0.05M}$ Oxalic acid solution (in our lab) we put NaOH in the burette whereas added phenolphthalein to oxalic acid in titration flask. But in this video the demonstrator does just opposite ( i.e., $\ce{NaOH}$ in flak with phenolphthalein). I am confused in deciding which one might be correct. My view is that either would do the job but I need some clarification.


texts: In rdkit, how to preserve stereochemistry in a SMARTS subgraph?

texts:
In rdkit, when doing a MCS search for molecules bearing a chirality center, (how) is it possible to preserve the stereochemical information when exporting the subgraph to a SMARTS string?

Consider the following three molecules:

>>> mol_ccw = Chem.MolFromSmiles('C1=C[C@H](Cl)CCC1')
>>> mol_cw  = Chem.MolFromSmiles('C1=C[C@@H](Cl)CCC1')
>>> mol_lin = Chem.MolFromSmiles('C=C[C@H](Cl)CCC')

Doing a chirality-sensitive subgraph search leads to the somewhat expected result:

>>> rdFMCS.FindMCS([mol_ccw, mol_cw], matchChiralTag=True).smartsString
'[#6](=[#6])-[#6]-[#6]-[#6]-[#6]-[#17]'
>>> rdFMCS.FindMCS([mol_ccw, mol_lin], matchChiralTag=True).smartsString
'[#6]=[#6]-[#6](-[#17])-[#6]-[#6]-[#6]'
>>> rdFMCS.FindMCS([mol_cw, mol_lin], matchChiralTag=True).smartsString
'[#6]-[#6]-[#6]-[#6]-[#6]'

The subgraph over mol_cw and mol_lin includes the stereocenter. But unfortunately, the chirality information is not stored in the SMARTS string, and using [#6]=[#6]-[#6](-[#17])-[#6]-[#6]-[#6] for a chirality-sensitive substructure match leads to the expected result of the pattern made from that SMARTS string matching all three molecules:

>>> patt = Chem.MolFromSmarts('[#6]=[#6]-[#6](-[#17])-[#6]-[#6]-[#6]')
>>> len({mol_cw, mol_ccw, mol_lin}.GetSubstructMatches(patt, useChirality=True))
1

Manually inserting a lazy @H or a &*&H1 at the stereocenter leads -of course- to the desired result:

>>> patt = Chem.MolFromSmarts('[#6]=[#6]-[#6@H](-[#17])-[#6]-[#6]-[#6]')
>>> len({mol_ccw, mol_lin}.GetSubstructMatches(patt, useChirality=True))
1
>>> len(mol_cw.GetSubstructMatches(patt, useChirality=True))
0

Now, when matching mol_ccw and mol_lin, how do I get the stereochemistry-aware SMARTS string [#6]=[#6]-[#6&*&H1](-[#17])-[#6]-[#6]-[#6] as the substructure in the first place?


texts: Why use a salt bridge at all in an electrochemical cell?

texts: I was reading about electrochemical cells and I really don't understand why a salt bridge is needed. Can't you just combine the solutions? I've found a lot of webpages explaining electrochemical cells but strangely enough none of them seem to find this important enough to explain. All thoughts appreciated :)


texts: Does H+ in the ocean bind with water to form H3O+ or with carbonate ions to form HCO3-?

texts:
I've read so many references on the Internet about ocean acidification and basically it can be described by the following equations
This is when $\ce{CO2}$ dissolves into ocean to form $\ce{H2CO3}$: $$\ce{CO2 + H2O <--> H2CO3 <--> H+ + HCO3-}$$
This is when excess $\ce{CO2}$ reacts with pre-existing carbonate ions to form additional bicarbonate: $$\ce{CO2 + H2O + CO3^2- -> 2HCO3-}$$
Based on the two equations, I can tell that $\ce{H+}$ which are positively charged are consuming $\ce{CO3^2-}$ which are negatively charged and good for shells to make unnecessary bicarbonate, so my first thought was to remove $\ce{H+}$ only. But then my chem teacher said that $\ce{H+}$ can also bond with $\ce{H2O}$ to form $\ce{H3O+}$ and that needed to be separated back into water and $\ce{H+}$ and only then can $\ce{H+}$ be removed.

I'm so confused, are both methods the same? And any suggestions on how I can attract hydrogen ions together?


texts: Possibility of π–π stacking in non-aromatic systems

texts:
Is it possible to have π–π stacking for non-conjugated double bond systems?

For example, can the carbonyl groups of two urea molecules participate in π–π stacking? Although urea prefers to stay in hydrogen bonded form.

I would be really happy if you cite some resources (research paper, book, etc.) while answering.


texts: Titration of magnesium sulfate with potassium permangante

texts:
One common method for measuring the amount of $\ce{Fe^2+}$ in $\ce{FeSO4}$ is by dissolving it with $\ce{H2SO4}$ and then titrating with $\ce{KMnO4}$.

However, is it possible to measure the amount of $\ce{Mg^2+}$ ion in magnesium sulfate by dissolving it in $\ce{H2SO4}$ and then titrating it with $\ce{KMnO4}$? Why or why not?


texts: "Encyclopedic" / semi-exhaustive reference work on Chemistry

texts: I'm buying my brother a present—It's the holiday season after all. He's about to start his academic career in chemistry. I would like to give him a book on chemistry, but not something that is considered "chem 101", "popular", or too specialized and probably off-topic. I am a mathematician myself, and in my field we have the beautiful "Princeton companion to mathematics". It is edited by a Field's medallist, has contributions of many high-profile mathematicians, and is both incredibly varied and in-depth. It contains many, many beautiful phenomena, but is by no means a "popular book" or an easy read. I was wondering if anything like this exists in Chemistry. So to clarify: the book would ideally introduce an advanced reader to several concepts in other branches of chemistry than the person's speciality, in a way that is appealing to a serious academic. Many thanks!


texts: What chemicals could absorb/adsorb ambient atmospheric methane?

texts:
From an article in the New Scientist in 2010,

  Since pre-industrial times, methane levels in the atmosphere have risen from around 715 parts per billion to nearly 1800 ppb, claims Folberth. "If methane could be taken back to pre-industrial levels it would bring about half a degree of cooling and would be equivalent to removing one-third of anthropogenic carbon dioxide," says Folberth. Furthermore, the cooling would take place within 10 years.

Klaus Lackner and others have developed technology such as the moisture-swing sorbent to capture ambient $\ce{CO2}$

Where might be the chemical options for a material that would absorb or adsorb ambient methane?


texts:
I there a Good Version of a printable Periodic table Which is minimalistic and gives necessary information only such as -

At. Number
Element Name
At. weight
Shell configuration
color coding of various groups or Series


texts: Is Internal Energy = (3/2)nRT for a ideal monoatomic gas?

texts:
Internal Energy is a state variable and its value at a particular state cannot be measured; only the change in internal energy can be measured. So how come we write that
$$U=\frac32nRT$$
where
$U$ = internal energy of the system,
$n$ = no of moles of the gas,
$R$ = Universal gas constant,
$T$ = Temperature of the system.

Till now, I knew that it was 'Avg Kinetic energy' that followed the above relation that is  $\mathrm{K.E.} = (3/2)nRT$, but today while looking at a video in Khan Academy, I came across the relation $U=(3/2)nRT$ and got entirely confused.


texts: How is laughing gas produced in the Nef reaction?

texts:
I can't think of a mechanism for this reaction to give laughing gas.

Attempt:

I used the base to take out the acidic hydrogen at alpha position with respect to nitro group, but that makes the intermediate formed even more unstable. What should be the proper mechanism?


texts: Electrolysis of molten nitrates, sulphates and carbonates

texts:
We know that nitrates, sulfates and carbonates doesn't or hardly oxidized by anode in the aqueous solution.

What will be produced on anode in the electrolysis of molten salts of these ions?


texts: Why cannot nitrosonium ion attack aniline in electrophylic aromatic substitution?

texts:
This is the nitrosonium ion, which is produced by the reaction of $\ce{NaNO2}$ and $\ce{HCl}$:

[Image source: Wikipedia]

And this is the reaction between aniline and nitrosonium:

[Image source: Wikipedia]

Cannot it take place as an EAS, and with substitution at the ortho or para positions? The amino group is a very good activating group for EAS after all.

Update: I forgot to mention that EAS is observed in case $\ce{-NR2}$ is attached to the ring in place of $\ce{-NH2}$.


texts: How come water would not affect the results of a titration?

texts:
We were told to rinse the buret with the base so that the concentration won't be messed up, but when it comes to the flask that is going to hold the acid, there is no need to rinse, because it would not affect the result if it has water in it.

Why is that? Wouldn't the acid be diluted a little bit and that throws off the accuracy?


texts: Why cupric ion oxidises iodide to iodine

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I have learnt in the qualitative analysis of cupric ions that upon treating its aqueous solution with excess $\ce{KI}$, triiodide ions are formed which can be further tested using starch.
The explanation provided is that $\ce{Cu^2+}$ ions oxidise iodide ions to iodine which combines with additional $\ce{KI}$ to form $\ce{KI3}$.
$$\ce{2Cu^2+ + 2I- -> 2Cu+ + I2}   \tag1$$
$$\ce{I2 + KI -> KI3 }   \tag2$$
I looked up the reduction potentials of cupric to cuprous and iodine to iodide, and noticed that the latter is greater than the former.

I figured that maybe the reaction is reversible and lies to the left but the little amount of iodine formed is sufficient to turn starch blue black as it is a sensitive test.
But my doubt stems from the fact that it is generally regarded that cupric ions can oxidise iodide to iodine and also that cupric iodide does not exist (at least not in aqueous solutions). These statements would imply that the reaction (1) would lie to the right hand side which according to me should not be true.
Is it true that the reaction (1) actually lies to the right possibly due to formation of cuprous iodide which is a precipitate and the triiodide complex.
If not, then wouldn't it be incorrect for us to say that cupric ions oxidise iodide ions?


texts: Cheap metal to replace platinum in hydrogen fuel cell

texts: Platinum is used as a catalyst in hydrogen fuel cells because it increases the efficiency. However, if I just want to make a fuel cell for demonstration purposes, I don't want to use a lot of money to buy platinum wires. What "common" metal (aluminium, iron, etc.) works the best for a hydrogen fuel cell?


texts: Explaining the Relative Energies of Various Vibrational Modes

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Specifically, I'm wondering why it is that the asymmetric stretch in most (although there are exceptions to this I believe) molecules is higher in energy than the symmetric stretch.

Similarly, I would like a nice, physical (ideally quantitative/mathematical) explanation of why bending modes are usually lower in energy than stretching modes.

I can rationalize this second question on the basis of electrostatic forces. That is, any distortion from the minimum of the potential energy well will either cause more coulombic-type attractive forces or more coulombic-type repulsive forces. These forces should not be as large for a lateral displacement (bending) than for a stretch of some kind. This makes sense because the change in radius will not be as large when simply moving to the side from an equilibrium position. Of course, the change in radius is significant because electrostatic potential energy goes as $\frac{1}{r}$.

Anyways, that's a pretty classical answer, so I wonder how both of those questions can be explained more quantitatively as well as quantum mechanically.


texts: How is latent heat of vapourisation utilized in changing state?

texts: If latent heat of vapourisation is utilized in overcoming intermolecular forces of attraction between the participle of a material then how is it still hidden there? If latent heat is used in overcoming forces of attraction between the particles of a material then why doesn't it increase the kinetic energy of the particles of that material?


texts: Is an SN1 mechanism feasible with allylic or benzylic halides as substrates?

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My teacher stated that allylic carbocations are comparable in stability to tertiary carbocations. $\def\SN#1{\mathrm{S_N}#1}$

With this in mind I am confused why question 13 of this MIT practice test states that these two molecules are only expected to undergo $\SN 2$ reactions:

An $\SN 1$ reaction on the first molecule with the phenyl substituent would yield a primary carbocation, yes, but this primary carbocation is also benzylic, and can be stabilized through resonance.

An $\SN 1$ on the second molecule similarly yields a carbocation, but this is an allylic carbocation, and can easily be stabilized through resonance and delocalization of pi-electrons.

So, would $\SN 1$ be valid pathways of reactions for both of these molecules, or is $\SN 2$ simply the only pathway for these molecules to react?


texts: Is the Nitrogen in pyridine electron withdrawing and what effect does this have on electrophilic substitution?

texts: If I were to attempt to nitrate Pyridine (essentially benzene but with one carbon replaced with Nitrogen) would I get substitution at the Ortho-, Meta- or para position? Also why is this? I can only think of an inductive effect that the Nitrogen might have but I can't think of more factors and I also can't think whether it will be directing towards o-,m- or p- nor why. Can you help?


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A sample of water has its hardness due to only $\ce{CaSO4}$. When this water is passed through on anion exchange resin, $\ce{SO4^2-}$, the $\ce{SO}$ ions are replaced by $\ce{OH-}$. A 25.0 mL sample of water so treated requires 21.58 mL of 0.001 M sulfuric acid for its titration. What is the hardness of water expressed in terms of $\ce{CaCO3}$ in ppm? Assume the density of water is 1.0 g/mL.

I do not understand where does $\ce{CaCO3}$ come from if we started with $\ce{CaSO4}$at the beginning.


texts: Mixing two containers of each water and ethanol to varying degrees of purity

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In the following question, the water/wine mixing problem was recast in chemical terms. However, partial molar volumes can make this a much more challenging problem than it appears on the surface.

https://chemistry.stackexchange.com/questions/33579/wine-water-mixing-problem

For example, consider a container of $\pu{10 L}$ of ethanol and another container of $\pu{10 L}$ of water. To make a point, let's transfer $\pu{5 L}$ of ethanol to the water container and then transfer $\pu{5 L}$ of the water/ethanol solution back to the ethanol container. What is the purity in each container at the end?

We need to consider that mixtures of water and ethanol have less volume than the two do separately:

For example, after the first transfer, the water container contains $\pu{10.000 kg}$ of water and $\pu{3.945 kg}$ of ethanol for a total mass of $\pu{13.945 kg}$. However, we need to compute mole fraction to determine the volume of the solution:

$$\begin{array}{c|c|c}
\ & \text{water} & \text{ethanol}\\ \hline
\text{mass in kg} & 10.000 & 3.945\\ \hline
\text{moles} & 555 & 85.6\\ \hline
\text{mole fraction} & 0.866 & 0.134
\end{array}$$

From our graph, it looks like we have an excess volume of $\pu{-0.75 mL/mol}$. Since we have total moles $=640.6$, we have an excess volume of $\pu{-0.75 mL/mol}\times \pu{640.6 mol}\times \pu{1 \times 10^{-3} L/mL}= \pu{-0.480 L}$. Thus the actual volume is not $\pu{15 L}$ but more like $\pu{14.5 L}$.

If we transfer $\pu{5 L}$ back, we are left with less than $\pu{10 L}$ in the water container. We will also have less than $\pu{10 L}$ in the ethanol container!

  What volume $V_1$, as a fraction of the original volume $V_0$, needs to be transferred in order for both containers to have the same final purity?


texts: What common observations in chemistry were unexplainable by an early twentieth century chemistry who had no knowledge of relativity

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I was reading quite a well-known paper titled 'Relativistic Effects in Structural Chemistry' by PEKKA PYYKKO, and in it, he states that 'it was not until the 1970s that the full relevance of relativistic effects in heavy-element chemistry was discovered.'
I was just wondering if anyone could explain to me from the perspective of a chemist in the early twentieth century who would not have considered the importance of relativistic effects, what were some commonly observed phenomena that at the time chemists were unable to explain, but that today we know can easily explain using special relativity.
For instance I am aware that some chemical differences between silver and gold received a great deal of attention during the history of chemistry, although I am not quite sure why.


texts: Concentration of a substance in a solution

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Will the Concentration of any dissolvable substance be uniformly distributed in any type of liquid?

I am willing to read more about this topic , so if you have good suggestions for helpful books , please share it with us


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Chemical properties: Sodium metal and sodium amide ($\ce{NaNH2}$ ) are strong bases. They react with ethyne to form sodium acetylide with the liberation of hydrogen gas.

How can a metal considered a base (that too strong)? To act as base it should either donate a pair of electrons (in this case it's single electron) or accept proton or give $\ce{OH-}$ ion but here it's not qualifying any one. So is that statement wrong?

Formation of monosodium ethynide:
$$\ce{HC#CH + Na -> HC#C^-Na+ + 1/2H2}\tag{13.59}$$
Formation of disodium ethynide:
$$\ce{HC#C^-Na+ + Na -> Na+C^{-} #C^-Na+ + 1/2H2}\tag{13.60}$$

Source: NCERT 11, Hydrocarbons, Page 386