texts: Does minimizing ANY type of energy ALWAYS predict a state of equilibrium?

texts:
My intuition says no, but I am having trouble coming up with concrete examples.

I know that minimizing Gibbs free energy predicts a state of equilibrium, while minimizing kinetic or internal energy does not correspond to equilibrium. However, I am not so sure about potential energy--- when PE is at a minimum, is the system also at equilibrium?


texts: My professor said that in order to have PI, both + and - charge have to exist, and therefore phosphoric acid cannot have a Pi. I am confused because I can't find any definition that states both + and - charge need to exist on text or online. Online, the definitions of PI indicates something similar to "at which the molecule carries no electrical charge." So why can't H3PO4 be PI if it the molecule has 0 charge?


texts: Why should ether O be named as OXA in a bicyclo ring when it is a substituent?

texts:
I was asked to name the molecule below .

For the following molecule, since ether is a substituent here (keto is more prior group) my answer was:

3-methoxy-6-methy-7-oxy bicyclo[2.2.1]hept-5-en-2-one

.

My answer is wrong. The correct answer is

3-methoxy-6-methyl-7-oxabicyclo[2.2.1]hept-5-en-2-one

My point is, at C-3, ether is methoxy, but at 7 the same ether is OXA. Ether as substituent outside the bicyclo ring is alkoxy, but inside bicyclo compound it is OXA.
My question is, why should ether O be named as OXA in a bicyclo ring?


texts: PLGA - poly(lactic-co-glycolic acid) Synthesis

texts: Does anyone have experience with the synthesis of PLGA?  PLGA is synthesized by means of ring-opening co-polymerization of two different monomers, the cyclic dimers (1,4-dioxane-2,5-diones) of glycolic acid and lactic acid. PLGA is very expensive, due to its production costs. Can someone explain why is this synthesis process so expensive?


texts: Why is the bond energy for a C=O bond higher in CO2?

texts:
I was looking at the table of bond energies, and what caught my eye was how the bond energy for a $\ce{C=O}$ bond is $\pu{736 kJ/mol}$ with the exception of the $\ce{C=O}$ bonds in $\ce{CO2}$ being $\pu{799 kJ/mol}$.
What causes $\ce{CO2}$ to make such a  big difference in a $\ce{C=O}$ bond?


texts: Can you tell me the name of this ester? It is two $\ce{C8}$ fatty acids ester-linked with a molecule of 1,3-butanediol in the middle. I would be tempted to say (R)-butanediol-1,3-diyl dihexanoate, but I am really not sure.


texts: Difference between electropositivity and electronegativity

texts:
Sodium is more electropositive than hydrogen although they are in the same group.

Why is the electronegative value of hydrogen greater than sodium (metal)?


texts: What are the precise conditions under which benzene undergoes ozonolysis? All anyone can tell me is that it undergoes ozonolysis under "vigorous" conditions. But, what vigorous conditions?


texts:
Which of the following pyridines are most basic?

I would've considered D, since chlorine is the most electronegative, and would therefore have the largest partial negative charge, making it more basic than the nitrogen substituent. The answer given, however, is B. How can I reason this for myself?


texts: When mixed with water how does gypsum act as  a binder in creating concrete?


texts: What would a diagram of the metal lattice structure of CuSO4 look like?

texts:
Just as $\ce{NaCl}$ would look like this:

What would a diagram of $\ce{CuSO4}$ look like?


texts: Role of catalyst in elementary reactions towards rate law

texts:
We do know that the concentration of a catalyst might affect the rate of reaction. But what if the catalyst is included in the rate law? For example,
$$\ce{O3 + M <=>[$k_1$][$k_{-1}$] O2 + O + M},\tag{1}$$
where $\ce{M}$ is the catalyst, when I am writing the rate change of $\ce{O},$ do I write
$$\frac{\mathrm d[\ce{O2}]}{\mathrm dt} = k_1 [\ce{O3}][\ce{M}] - k_{-1}[\ce{O2][O][M}],\tag{2}$$
or
$$\frac{\mathrm d[\ce{O2}]}{\mathrm dt} = k_1 [\ce{O3}] - k_{-1}[\ce{O2][O}]?\tag{3}$$
Which is correct?


texts: What are range and domain of Hamiltonian? Hamiltonian is function so it should have ones. What are they?


texts: Why do conjugated dienes undergo Diels-Alder reactions?

texts: If conjugated dienes are so stable, why can they still undergo Diels-Alder reactions ([4+2] cycloaddition)?


texts: What exactly happens to mass during deuterium fusion?

texts:
I know that the mass of Helium-4 is slightly less than the mass of 2x Deuterium it may be made of and that it is the reason fusion gives a lot of energy.

But where exactly is this missing mass taken from? Aren't those 2 protons, 2 neutrons and 2 electrons forming Helium-4 atom the same as they were in previous Deuterium atoms?


texts: Can I use the hypotenuse of the pythagorean theorem to compute the work?

texts: A friend of mine told me that she used the hypotenuse of the pythagorean theorem to compute the work in graph below and the to compute the coefficient of efficiecy in this thermodynamics triangle cycle. What do you tnink about?


texts:
The solubility product of $\ce{AgBr}$ is $7.7 \cdot 10^{-13}\:\mathrm{mol^2/L^2}$.
What was the initial concentration of $\ce{AgNO3}$ solution, if the precipitation of $\ce{AgBr}$ appears after the addition of $20\:\mathrm{mL}$ of a $0.001$ molar solution of $\ce{NaBr}$ to $500\:\mathrm{mL}$ of the $\ce{AgNO3}$ solution.

I got the solution as $0.054\:\mathrm{M}$. I'm confused with the procedure. This is what I have done.

Precipitate occurs at $K_{sp}=Q$ and $Q=[\ce{Ag+}][\ce{Br-}]$
$[\ce{Ag+}] = [\text{(Vol of $\ce{AgNO3}$)}\cdot\text{Molarity} ] / \text{Total Volume of the mixture}$
Similarly for $\ce{Br-}$
$[\ce{Ag+}][\ce{Br-}] = 2\cdot10^5$

The answer I got it $0.054\:\mathrm{M}$ ? Is that correct ?


texts:
I used drain opener (sodium hydroxide and sodium hypochlorite) in an RV and accidentally caused it to drain out (mixed about 1:10 with water) onto concrete below.

There is a fairly strong smell.

How quickly will these chemicals decompose?

What will they decompose into?

How fast will the smell go away?


texts: What is the equation for the reduction of water?

texts:
I'm a grade 12 student trying to understand redox reactions. What's the equation for the reduction of water?
The back of my textbook says: $\ce{2H2O + 2e- -> H2 + 2OH-}$
I get that this makes sense, but I have no idea how to derive it myself. Any help would be appreciated!


texts: How to draw Fischer projections for carbon chain having more than two carbons?

texts:
How can we draw Fischer projections for one-five carbon compounds?

For example, say we have pentane-2,3,4-triol ($\ce{CH3-CHOH-CHOH-CHOH-CH3}$; image below). With wedge and dash structure, the alcohol group is below the plane for the 2nd and 4th carbons but above if for the 3rd carbon. How can we draw the Fischer projection of this compound?

I read an extract from the chapter about carbohydrates in Solomon's book (10th edition) but only understood partially how to draw Fischer projections as it is given very briefly. Also, a brief introduction is given in chapter 5 but it is for two-carbon compounds only.

I have tried a lot but cannot understand how to construct it or what are the conventions on which they are made. Apparently, the web doesn't describe Fischer projections in a very detailed way probably because they are generally only used in biochemistry.


texts:
34.05 mL of phosphorus vapour weighs 0.0625 g at 546 °C and 0.1 bar pressure. What is the molar mass of phosphorus?

I tried to solve the above question and got 1249.8g. The book's answer sheet lists the answer to be 1247.7 g.

I don't understand how the heck that happened? I'm pretty sure a mole of phosphorous doesn't weigh more than 1.2 kg.


texts: How to Convert Sucrose to Glucose and Fructose

texts:
If you have some sort of sports drink that contains sucrose, how would you take that sucrose and break it down into its components, glucose and fructose? I know that sucrose + water will break it apart, but how can it still remain together (as sucrose) while in the bottle of sports drink?

I am trying to compare the levels of glucose in various sport drinks. So I'm planning to use Benedict's solution and a spectroscope in order to determine the amount of glucose present in solution (I'm going to add activated charcoal to the solution to remove the colouring from it before placing in the spectroscope).

I will prepare standards by adding 5 grams of glucose to 100 mL of water, 10 grams of glucose to 100 mL water, and so on.

As a high school student I only have limited resources. Any information about my proposed plan or alternatives that are low-cost are appreciated.


texts: How can I figure out if my store bought chlorine is the percentage it says it is?

texts:
Chlorine is an important part of maintaining any pool. I've read horror stories of people buying chlorine from pool stores or big box stores and the chlorine being ineffective.

If stored long enough Chlorine can degrade, lose it's strength. If put in the sun i've read that it can speed up that process.

Like most pool owners, I have a pool test kit that tests how much chlorine is in a pool water sample. I specifically own a Taylor K-2006c Kit which test for Free Chlorine using the FAS-DPD Method.

At most pool stores they supply 12.5% Sodium Hypochlorite and 87.5% Other Ingredients.

With my given test kit would it be possible to accurately test whether or not it's actually 12.5% Sodium Hypochlorite or not? If so, how would I go about doing so?

If not; What do you recommend using in order to test the chlorine.


texts: How likely is it for monocalcium phosphate to spontaneously convert to dicalcium phosphate?

texts:
I'm trying to make liquid fertilizer by dissolving triple superphosphate (TSP) into water. TSP is supposed to be $\ce{Ca(H2PO4)2·H2O}$, which is quite soluble in water ($\pu{2g/100mL}$). The manufacturers also advertised it as "almost completely soluble in water."
However, I couldn't get it to dissolve despite never exceeding $\pu{1g/100mL}$. The TSPs are obtained from various manufacturers, all of which are equally insoluble. I did not weight the insoluble particulates, but visually it was clear that very little of the TSP dissolves. I also tried crushing the insoluble particulates, but they were as solid as rocks. I have also tried turning them into powder, but still equally insoluble.
Wikipedia stated that:

Samples of $\ce{Ca(H2PO4)2}$ tend to convert to dicalcium phosphate:
$$\ce{Ca(H2PO4)2 → Ca(HPO4) + H3PO4}$$

Dicalcium phosphate is much less soluble in water ($\pu{0.02g/100mL}$). If monocalcium phosphate can spontaneously convert to dicalcium phosphate, maybe this is happening on the TSP fertilizer.
All processes of converting monocalcium phosphate to dicalcium phosphate I had found requires intervention (e.g. this patent). How likely is it for this process to happen spontaneously?


texts: Physical state of the carbon denoted with "gr"

texts:
I would like to know what does a gr mean when used to represent the physical state of the carbon, for example, in the synthesis of the glucose

$$\ce{6C_{(gr)} + 6H2_{(g)} + 3O2_{(g)}-> C6H12O6_{(\ell)}} \quad,$$

what does the $\mathrm{gr}$ mean?


texts: How are there two C3 rotation axes in ammonia?

texts:
If we look at the character table for the $C_\mathrm{3v}$ point group (which $\ce{NH3}$ is an example of), we see that these are the symmetry elements ${E, 2 C_3, 3 \sigma_v}$ present in the molecule. My question is — why are there $2 C_3$ rotation axes? Shouldn't there be only one, which is perpendicular to the plane containing the three hydrogens?
The $C_\mathrm{3v}$ character table:
$$\begin{array}{c|ccc|cc} \hline
C_\mathrm{3v} & E & 2C_3 & 3\sigma_\mathrm{v} & & \\ \hline
\mathrm{A_1} & 1 & 1 & 1 & z & x^2+y^2, z^2 \\
\mathrm{A_2} & 1 & 1 & -1 & R_z &  \\
\mathrm{E} & 2 & -1 & 0 & (x,y), (R_x,R_y) & (x^2-y^2,xy), (xz,yz) \\ \hline
\end{array}$$


texts:
Upon coming back to University I've started studying basic chemistry again. I've always had trouble with the concept of "moles". According to my study book,

  1 mole of any element or compound is equal to its molecular weight in
  grams.

I understand that part but later in the paragraph it also says:

  One mole of any substance always contains exactly the same number of solute particles, that is, $6.02 \times 10^{23}$ (Avogadro's number). So whether you weigh out 1 mole of glucose (180 g) or 1 mole of water (18 g) or 1 mole of methane (16 g), in each case you will have $6.02 \times 10^{23}$ molecules of that substance.

If 1 mole equals the molecular weight of a compound, then how come 1 mole of glucose doesn't equate to 1 molecule of glucose? Basically, why is 1 mole of glucose $6.02\times10^{23}$ molecules instead of 1 molecule?


texts:
I've always been told soap is basic in pH. A few years back in a high school chemistry class, we measured the pH of various substances with universal pH indicator. We measured some liquid hand soap and it came out as acidic, which puzzled even the teacher. Unfortunately I have no idea what brand it was and I still don't know why it came out as acidic.

I learned yesterday that the fundamental reaction that produces soap happens when a base reacts with an oil chain which breaks down the glycerol backbone. Depending on which exact reaction path is being used to make the soap, some base may be added to ensure no oils remain unreacted. After the reaction is complete, some acid can be added to neutralize the base. Could it be likely that extra acid was added to the soap to neutralize the remaining base and the solution was left acidic? What other possible ideas could explain why the soap was acidic?


texts: Temperature of chlorine gas at given pressure and volume

texts:
Chlorine is widely used to purify municipal water supplies and to treat swimming pool waters. Suppose that the volume of a particular sample of $\ce{Cl2}$ has is $\pu{9.22 L}$ at $\pu{1124 torr}$ and $\pu{24 ^\circ C}$. At what temperature will the volume be $\pu{15.00 L}$ if the pressure is $\pu{8.76e2 torr}$ ?

I found the moles of the sample to be $\pu{0.559 mol}$. However, now I'm stuck at the last part of the question. Can I use $\pu{0.559 mol}$ to solve for the temperature when the volume is $\pu{15 L}$ and the pressure is $\pu{8.76e2 torr}$?


texts: How to determine from the formula that there is a phenyl group present in the molecule?

texts:
Why is the organic compound $\ce{C6H5-CH=CH-CH2Cl}$ named 3-chloro-1-phenylprop-1-ene and not 9-chloronon-5,7-dien-1,3-yne even though there is no specification whatsoever that there is a phenyl group in the organic molecule?
$$\ce{C6H5-CH=CH-CH2Cl}$$
can also be written as
$$\ce{CH#C-C#C-CH=CH-CH=CH-CH2-Cl}$$
and the name for this organic compound would be 9-chloronon-5,7-dien-1,3-yne.
How do we surely know that there exists a phenyl group in the molecule?
Also why is phenyl treated as a substituent and cannot be considered in the longest chain?


texts: Why do esters have to be distilled during purification?

texts:
I am currently designing a lab experiment for a school project in which I am to determine the effect of catalyst concentration ($\ce{H2SO4}$) on the rate of reaction between methanoic (formic) acid and ethanol to create ethyl methanoate. I plan to do this by varying the concentration of sulfuric acid at the beginning, and comparing the end yield of ester.
$$\ce{HCOOH +C2H5OH <=>[varied concentrations of H2SO4] HCOOC2H5 + H2O}$$

I am aware that distillation is a crucial step following reflux in pretty much every esterification for purification, but why? Can't one simply wash the crude ester with deionised water to catch all remaining ethanol, use CaCO$_3$ to neutralise the acids, and filter off via a separatory funnel?

I am asking this because my school project has a set timeframe for all experiments of officially 8 hours over two weeks, in which it is recommended that I conduct at least '5 measurements at 5 intervals'. I know I won't reach this, even if I reflux each of my esters for 10 minutes because of the distillation.


texts: Anthocyanins as pH-indicators: stop the titration at red, purple or blue?

texts:
If you titrate some hydrogen bromide solution (0.1 M) to some sodium hydroxide in order to determine the exact concentration of hydrogen bromide (0.1 M), and you use anthocyanins as a pH indicator. This anthocyanin will be red if you have a low pH value and purple if it is slightly acidic until it is slightly basic. It will be blue if the solution is basic.

Do you have to titrate until the color of the solution is blue or purple?

Equilibrium from red to purple: $$\ce{H2X+ <=> HX}$$

$K_a = 1.047*10^{-3}$

Equilibrium from purple to blue: $$\ce{HX <=>X^{−}}$$
$K_a = 3.16 * 10^{-8}$


texts: Viscosity of branched vs. linear short alkanes

texts: I was looking through the CRC Handbook of Chemistry and Physics section on liquid viscosities, trying to explain trends in viscosities. In higher alkanes, the viscosity increases with the degree of branching, which is logical. However, I noticed for lower alkanes, the opposite is true. For example, 1-methylbutane has a viscosity of 0.286 mPa-s at 25 C, whereas its linear counterpart pentane has a viscosity of 0.30 mPa-s at 25 C. The same trend holds for alkanes with 6 carbons. These trends go against my chemical intuition and I cannot think of a sound explanation, which brings me to my question: why is the viscosity lower for branched vs. linear alkanes in the lower alkanes?


texts: How much time for a water molecule in pure water to reach the top of a glass of water?

texts:
I have a curiosity to know how long it will take for a water molecule to move a certain distance in pure water. I can put it simply as how much time for a water molecule to travel the whole length of a typical glass of water if no collective motion is present (therefore very still water with no convective currents).

To simplify things, this is the model:

Suppose I have a completely still and ideally insulated glass of water where the temperature in each part of the fluid is exactly the same (therefore no convective motion).      In addition the top of the glass container is closed and no water air interface is present to avoid evaporation that if present changes the dynamic.    In addition the glass of water is big enough so that the dynamic of the water in the core is not influenced by the the limited range of motion of the water near the borders of the glass.
Since it is a liquid, the water molecules move around each others until the original water molecule is at distance r from where it started(A). In absence of gravity the movement is equally probable in all directions, while with gravity I suppose it may be more likely a layer layout of the water molecules making horizontal movements more likely (see elipse shape of the trace).
The questions are (no need to reply to both):
1) How much time to be at distance r in both situations (gravity or not)? (it will depend on temperature, so let's say at room temperature)
2) How much time roughly will it take for a water molecule to reach reach almost the top of a typical glass of water starting from the bottom?    (in absence of convective motion and evaporation)


texts: Reaction of primary nitroalkane with nitrous acid

texts:
I was reading the reaction of primary nitroalkane with nitrous acid. I read this reaction

Another mechanism which I saw:

I am now confused  whether the first mechanism occur or the second one.I tried to search it on google but didn't get anything which could clear this doubt .Please help me regarding this.This I need to know because the reaction written in my book after 2nd reaction is-

If 1st reaction is right then what will occur after adding $\ce{NaOH}$ in the product. Also when I read Victor Mayer test the 1st reaction was written there. Due to this I am in a dilemma. Please explain.


texts: What do short-range and long-range corrections mean in DFT methods?

texts:
Currently I am looking for the most accurate calculation method for a simple non-conjugate molecule consist of C, N, O and H. Normally I would try each method for a similar and known molecule then compare them with the experimental results but I don't have anything to compare this time.

So I need to predict a method for ground state and excited state calculations. While I was searching I kept coming across the terms "long-range" and "short-range". In the original publication of CAM-B3LYP for example, the authors claim that CAM-B3LYP provides additional long-range corrections, the weak part of B3LYP. What does it suppose to mean to me? I was unable to find any definitions of these terms.

Any additional tips about choosing a method are appreciated, also.


texts: How do flame tests give off color if they only emit the colors when the electrons return to ground state?

texts: Since we are constantly holding the element in the fire and the elements only give off the color when the electrons emit the energy that was supplied and return to ground state, why do we only see the colors when in the fire and don't see the colors when we take the supplied energy ( i.e., the fire) away?


texts: Comparison of two spectra in order to find whether the irradiated sample has significantly different resulting spectra

texts:
I would like to compare two absorption spectra ( or interferograms) and conclude whether between these two there are statistically significant differences at particular wavelength intervals. At the moment, I have data of two experiments that look like this:
    # A tibble: 6 x 5
      t     x1     y1     x2     y2
  <dbl>  <dbl>  <dbl>  <dbl>  <dbl>
1 3999. 0.0124 0.0132 0.0122 0.0113
2 3998. 0.0125 0.0130 0.0122 0.0116
3 3997. 0.0122 0.0131 0.0122 0.0113
4 3996. 0.0121 0.0136 0.0122 0.0114
5 3995. 0.0124 0.0139 0.0122 0.0122
6 3994. 0.0125 0.0141 0.0122 0.0129

The first column represents the wavenumber, the x columns represent the absorbance of sample and the y columns represent the absorbance of irradiated sample ( before and after). I was wondering whether I could compare these data ( x and y) as time series and if so, what could be the method to quantify the differences, if any, between the samples before and after irradiation. Maybe it's already been done and there is somewhere some information as to how to compare the spectra if the wavenumber is interpreted as time ( x axis). I did the t test in R and in both experiments the null hypothesis could not be rejected, although for the second experiment (x2, y2) the p value was much lower than for the first.
If I average the x and y, and then plot both data, I see that there are visible differences at certain wavelength intervals. In R, I used IRISSeismic package and function crossSpectrum, that gave me such an output:
   freq        spec1        spec2 coh        phase             Pxx             Pyy
1   0.0002666667 2.121935e+01 2.152532e+01   1  0.010220252 1.856693e+01+0i 1.883465e+01+0i
2   0.0005333333 7.011069e+00 6.869078e+00   1  0.008984730 6.134686e+00+0i 6.010443e+00+0i
3   0.0008000000 8.385363e+00 8.197039e+00   1  0.011999039 7.337193e+00+0i 7.172409e+00+0i
4   0.0010666667 7.483070e+00 7.272319e+00   1  0.015419031 6.547686e+00+0i 6.363279e+00+0i
5   0.0013333333 4.086251e+00 3.899095e+00   1  0.017551350 3.575469e+00+0i 3.411708e+00+0i
6   0.0016000000 1.537709e+00 1.405562e+00   1  0.008722742 1.345496e+00+0i 1.229867e+00+0i

For all data points the coh index is given as 1. But obviously that doesn't help me to determine, whether the difference is substantial between two data sets.
I tried to average data points between groups (x1, y1 and x2, y2) at each wave number and plotted the graph, it looks like the difference might be significant at certain wavenumber interval. Maybe I could try to express one line ( averaged data points after irradiation of the sample) as a function of the other? But how?
Here is a project with similar experiments: https://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532015001202571 , for statistical analysis they use ANOVA and Tukey's test, but how do I do it for the vectored data?
I cannot find online anything. Here is something of the sort I am looking for: https://www.youtube.com/watch?v=gjKSfILE9nM He compares two spectra in Matlab, but he is using self made toolkit which I can not obtain. How can I do something like this in R? I've read something about modelling the data, but here, I don't have any variables just data of two spectra.


texts: How to estimate the dielectric constant of a liquid?

texts:
Are there any approximate relationships between the (static) dielectric constant of a liquid and properties of the individual molecules?

For example, suppose I know the polarizability and dipole moment of a molecule, as well as it's density in the liquid phase. Can I estimate the dielectric constant of the liquid from these quantities (or other similar ones)?


texts: Do the names of some elements have anything to do with planets?

texts: There are elements like neptunium and plutonium in the periodic table. Did their discovery have anything to do with Neptune and Pluto? Or are they randomly assigned with such names?


texts: In my homemade electrolysis setup, only the negative end bubbles?

texts: I've created an electrolysis setup by connecting a $6~\mathrm{V}$ battery to a cup filled with saline water via pencils; I am confused as to why only the negative pencil bubbles though. After running the setup for longer than five minutes, the water turns brown but so far that information has not been useful. Why is the negative pole the only one bubbling and if possible, why is the water turning brown?


texts:
I've several doubts about this ICHO synthesis problem, which was a part of the preparatory problem package of 2018 (so yes, it's not a part of an ongoing contest)

Before sharing the answer given, I'd like to share my thoughts and efforts towards the problem -

The first step is clearly an oxidation step, performed in presence of the peroxy acid above the arrow; which is subsequently reduced to the corresponding carboxylic acid. The oxidation product should be an amine oxide, but the question is, which one? (We have three nitrogens to play with)
For the sake of continuation, let's assume A is what they expect it to be (check the image below). Now, I'd expect more than just one hydrogen of the ring to be replaced by deuterium in the base catalysed tautomerism step. What's the next step (acid catalysed) for? Also, in basic medium (1) the initial ester would undergo saponification to acid.
B to C is a reducing step. Pd/C in presence of formic acid is known to be a reducing agent, but how do we know it reduces the amine oxide back to amine? (It'd be great if some sources could be provided for this, I couldn't find any)

C to the final product is pretty direct, the carboxylic acid group converts to acyl halide which undergoes nucleophilic addition by the ammonia derviative.

Thanks a lot.

P.S. Only a sound explanation for the A to B conversion remains - rest has been taken care of by the first posted answer. Please make additions/include relevant stuff for other conversions if you find any.


texts: Why does carbon monoxide have a greater affinity for hemoglobin than oxygen?

texts:
Hemoglobin is an iron-containing oxygen transport metalloprotein in the red blood cells of most mammals. Simply put, it's a carrier protein. Interestingly it doesn't carry carbon dioxide in the same way it does for oxygen $\ce{O2}$. Oxygen binds to the iron atoms in the protein whereas carbon dioxide $\ce{CO2}$ is bound to the protein chains of the structure. Carbon dioxide doesn't compete with oxygen in this binding process.

However, carbon monoxide $\ce{CO}$ is a very aggressive molecule. It's a colourless, odourless, and tasteless gas that is lighter than air and can be fatal to life. It has a greater affinity for hemoglobin than oxygen does. It displaces oxygen and quickly binds, so very little oxygen is transported through the body cells.

There are two equilibrium reactions of binding oxygen and becoming oxygenated hemoglobin:

$$\ce{Hb (aq) + 4O2 (g) -> Hb(O2)4 (aq)}$$

$$\ce{Hb (aq) + 4O2 (g) <- Hb(O2)4 (aq)}$$

And carbon monoxide binding equation at equilibrium:

$$\ce{Hb (aq) + 4CO (g) ⇌ Hb(CO)4 (aq)}$$

It is said
 the equation is shifted towards right, generating $\ce{Hb(CO)4(aq)}$, since its bond is much stronger.

I have two main related questions:

Why is the carboxyhemoglobin bond stronger relative to that of oxygenated hemoglobin?
Why is carbon monoxide highly attracted to hemoglobin?

Does it have anything to do with the oxidation state of oxygen in each molecule? Please show some reaction equations associating $\ce{Fe}$.


texts: Why is a squared cosine window function commonly used for 2D spectra?

texts:
In nearly all default parameter sets for 2D NMR experiments on Bruker spectrometers, the window function is set to a pure squared cosine function for both dimensions (QSINE with SSB = 2). In contrast to that, 1D spectra are often processed with the efp command, which uses an exponential window function.

Why is the squared cosine window function the default? Which advantages and disadvantages does it have compared to other common window functions?


texts: Why does ethanol and water mixture show positive deviation from Raoult's Law?

texts:
So, my teacher said, "For a solution to show positive deviation from Raoult's Law, it must have a compound which is lacking hydrogen bond and a compound which has hydrogen bond."

This is because the compound not having a hydrogen bond breaks the hydrogen bond of the other compound.

Now, why does ethanol and water mixture show positive deviation? Both of them have hydrogen bonds.


texts: What's the purpose of a Grignard reagent initiation?

texts:
Preface: I've read this question about water preventing an initiation from occurring.

I understand why it's important to slowly add the alkyl halide to the dry ether and magnesium for exotherm control. But why is the first addition called an initiation and what's its purpose?

Is it just to confirm that the conditions are ready to continue slowly adding the rest of the reagent? I know it's a free-radical reaction, maybe that's where the term "initiation" comes from. But I've seen the reaction described as "self-sustaining" after the initiation, but it's not a chain reaction. Perhaps that's referring to a predictable reaction proceeding forward instead of stalling then blowing up your glassware.


texts: Clarifying question about chloride ions, water softening & corrosion

texts:
I have a question regarding the use of NaCl as a water softener.

Recently i was asked to comment on a series of test results from a water softening device were a lot of corrosion had occurred post softening. Just to be sure we are on the same page, NaCl was added to the water to dissolve* the CaCO3, Ca(CO3)2 & CaSO4.

*Ion exchange is not my field of expertise, so I'm not quite sure if this is the correct wording

Now, according to the folks who ran the test, there were no signs of ‘Chlorides’ in the water sample, what they mean by this is still unclear. I was also informed that no precipitate was collected. Now to the actual question: they wanted to know why the pipes used, post softening, had crevice corrosion inside the pipe. My first intuition was that there were still $Cl^-$ ions in the water which is causing the steel to corrode. However, the folks running the test assured me that the chloride had bonded with the calcium ions.

I’ve been trying to figure out what in the world could cause the pipes to corrode, assuming that they are correct, and the chloride have formed CaCl2.

Have you guys got any ideas? Have I misted something, or am i right to assume that the folks who ran the test don't know what they are talking about.

If you need any more information, feel free to ask. As stated earlier, this is not my field of expertise so if I'm wrong about something please correct me.


texts: Why is the inside of a cell both more acidic and more negative than its environment?

texts:
In a very simplistic way of thinking, an acidic solution has more positively charged $\ce{H+}$ ions present, whereas a basic solution has more negatively charged $\ce{OH-}$ ions present.

Can that be simply reconciled with the fact that (1) the intracellular pH of about 6.8 is more acidic than the intercellular pH of about 7.3, and that (2) a typical cellular membrane potential is -40 to -80 mV?


texts: Does the initial rate in the reaction of magnesium powder with nitric acid depend on the volume or the concentration of the acid?

texts:
For the question regarding the initial reaction rate, I don't quite understand why the answer is D.

If I calculated the number of moles from the volume and conc, I would get A=0.4 moles; B=0.2 moles; C=0.2 moles; D=0.1 moles

As original equation is 0.2 moles of NH3, at 25 degree Celsius, I chose C. But why is the answer D, given that it is 0.1 moles not 0.2 moles.

Thanks in advance and sorry for any wrong tags.


texts: How is the standard electrode potential measured without allowing the electrolyte concentrations to change?

texts:
Let's say we need to measure the standard electrode potential of a zinc electrode dipped in an aqueous solution of $\ce{ZnSO4}$. To do this, we use the standard hydrogen electrode(SHE)-the reference electrode-as the anode and the zinc electrode as the cathode, and measure the emf of the cell.

The electrolyte corresponding to the SHE is a solution whose hydronium ion concentration is 1M. To construct the zinc half cell, we dip a strip of zinc in a 1M solution of $\ce{ZnSO4}$(for the STANDARD value). We connect the two electrolytes(of the zinc electrode and the SHE) with a salt bridge. Now, we measure the emf of this cell using a high resistance voltmeter, to find the potential difference between the electrodes without allowing any significant current through the cell.

When the zinc strip is dipped in the solution, it initially has no excess electrons on it. It is just a neutral piece of zinc metal. Now an equilibrium will be established between the solid zinc and zinc ions in the solution, finally leading to an excess of electrons on the electrode and a specific concentration of zinc ions in the solution. This, and a similar process at the SHE would cause an electrostatic potential difference between the two electrodes, since the relative positions of the two equilibria would be different. The voltmeter measures this potential difference to be the emf of the cell.

Here's my question: In setting up the two equilibria, won't the concentrations of the electrolytes change? Initially the zinc electrode had zero charge. But later it acquires a negative charge. This means that a certain number of zinc ions had to join the solution, leaving behind the electrons on the metal. So the concentration of zinc ions in the solution would now have to be more than 1M. So how would the STANDARD electrode potential be measured? How would the electrode potential be measured at ANY arbitrary concentration of zinc ions? It seems to me that the electrode potential can only be measured when the resulting concentration of zinc ions is equal to the equilibrium concentration. Does such a concentration even exist? Similarly, how is the hydronium concentration of the electrolyte corresponding to the SHE maintained at 1M?

According to me, the concentrations have to change for any net charge to develop on either electrode, hence establishing a potential difference. How does a net charge develop on each electrode without the ion concentration in the solution changing?


texts: After cementing a wall, water is applied on the surface to keep it moist to maintain its strength for the next few days. Why is this necessary for maintaining the strength of the concrete?


texts:
How can hybrid orbitals be equivalent? Take, for example, $\mathrm{sp^3}$ hybridization. The wave functions of each hybrid orbitals are given by:

\begin{align}
\psi_1 &= \psi_s + \psi_{p_x} + \psi_{p_y} + \psi_{p_z}\\
\psi_2 &= \psi_s - \psi_{p_x} + \psi_{p_y} - \psi_{p_z}\\
\psi_3 &= \psi_s - \psi_{p_x} - \psi_{p_y} + \psi_{p_z}\\
\psi_4 &= \psi_s + \psi_{p_x} - \psi_{p_y} - \psi_{p_z}\\
\end{align}
No one of them has same linear combination. So, how can they be equivalent? I am not getting the sense.


texts: Why an asymmetric geometry with sp3d and sp3d3 hybridization?

texts:
A molecule in which the central atom is $sp^3d^2$ hybridized ($\ce{SF_6}$), for example, acquires an octahedral shape, which can be explained by assuming that the hybrid orbitals arrange themselves to minimize repulsion amongst themselves. An octahedron makes sense, it the only way to symmetrically arrange six hybrid orbitals on an atom. The case for an $sp^3$ hybridized atom is similar which from a similar logic can be explained to have a tetrahedral geometry.

But consider the case of $sp^3d$ hybrid orbitals which arrange themselves in a trigonal bypyramidal shape ($\ce{PCl5}$). This is a gross breach of the usual adherence to symmetry. Two bonds are at the axial location and three at the equatorial location. In fact, the axial bonds are slightly longer than the equatorial ones. The case for $sp^3d^3$ hybridization is similar ($\ce{IF7}$) with five orbitals crammed into the equatorial plane and two sticking out above and below it. Why are these arrangements preferred in favor of one with a simple symmetric arrangement of orbitals (which, I think, would minimize the repulsion)?


texts: How did Halogens become known as Halogens? They are not the only elements that form salts!

texts:
Having never given it a though before, I recently discovered (in a different context) that the prefix halo- actually means 'salt' or 'sea' and the suffix -gen means 'to form' or 'to generate'. So the Halogens are the elements that 'form salts'. But there are salts that do not have halogens in them, like $\ce{Na2S}$ or $\ce{(NH4)2SO4}$. Was it known at the time that other salts existed, and what other names for this group might have been considered?

On a side note, why aren't Group I metals called halogens? Doesn't it take two to tango (I mean, to form salts?)


texts:
How can I calculate the energy of a solution by knowing all of it's elements?

For example:

If I have 2 liters of salting water $\mathbf{NaCl_{(aq)}+H_2O_{(l)}}$ contains 1.5 g of salt, how can I determine the internal energy stored in it?


texts: Is there an opposite to shielding effect?

texts:
I recently read about shielding effect and lowering of effective nuclear charge  due to penetration of other electrons. I wonder while doing calculations involving Slater's rules the electrons from outer shells are neglected.
I think they can reverse the shielding produced by inner shell electrons.


texts: Why $\psi(r_e, r_n) = \sum \psi_e^i(r_e|r_n) \chi^i(r_n)$ in Born-Huang expansion?

texts:
Given a molecular system, the time-independent Schrodinger Equation (SE) that we want to solve is
$$\hat H \psi(r_e, r_n) = E \psi(r_e, r_n)$$
$\hat H$ is hermitian, so the set of solutions $\psi(r_e, r_n)$ are orthonormal.

Under Born-Oppenheimer approximation, $\{r_e \}$ decouples with $\{ r_n \}$, thus each $\psi(r_e, r_n)$ can be represented as
$$\psi(r_e, r_n) = \psi_e(r_e|r_n) \chi(r_n)$$
in which $\hat H_e(r_n) \psi_e(r_e|r_n) = E_e(r_n) \psi_e(r_e|r_n)$.

My confusions:

In every reference I read, the eigenfunction of $\hat H$ is represented as

$$\psi(r_e, r_n) = \sum_{i = 1}^{\infty}\psi_e^i (r_e|r_n) \chi^i(r_n)$$
in which {$\psi_e^i(r_e|r_n)$} is the set of eigenfunctions of $\hat H_e$

Why an eigenfunction of $\hat H$ can be represented in such a way? For me, this expression is just
$$\psi(r_e, r_n) = \sum_{i = 1}^{\infty}\psi^i (r_e, r_n)$$
it makes no sense that an eigenfunction can be expanded in some bases.


texts: Burning Of Coal and Black Body Radiation

texts:
Coal burns with a red glow.

What is the ignition temperature of coal?

If it is T, and I take another substance which has melting point quite above T,
and heat it to T, Will it also emit red light?


texts: Reason for the generation of London Dispersion Forces

texts:
While talking about gaseous state of matter we came to the topic of London Dispersion Forces while are caused by the generation of dipole in one atom which induces a dipole in another. While talking about the cause of such I stated that since Schrodinger's equation for multi-electron atoms is time dependent and hence at some moment a dipole may get generated (due to the increase in the probability of electrons in that region). Though as for now I am thinking that what I said was quite vague and may not be the reason for it.

So what is the reason for generation of dipole moment in one atom to cause the London forces?


texts: Correct Generalization for Adair Equation?

texts:
I know how to derive the Adair Equation for n binding sites the long way, writing n+1 mini equations and linking them to relate all sub $K_b$ values to $K_{b-intrinsic}$.

Tried to find a general formula for the adair equation and found different versions online.

If I raise $K_i$ to the ith power, does that make the generalization correct?

Thanks - studying for an exam.


texts: Volume changes when mixing DMSO and water

texts: Since I know that a mixture of 500ml $\ce{H_2O}$ and 500ml ethanol gives less than a liter of mixture I wonder how strong this effect is when mixing DMSO and $\ce{H_2O}$. I'd assume it's nonzero - but is it negligible?


texts:
What does it mean when there is a negative delta $S$ $(-\Delta S)$? One person asked if this implied negative entropy, but I don't see how this could be possible.

Does this imply a negative change in entropy? If the former, how can negative entropy exist?


texts: Slight FTIR band intensity changes across several different copper salt spectra: relevant for characterization?

texts:
I have several spectra of different samples which are probably all copper (neutral and/or basic) acetate(s) and which are very similar. I present them overlayed and (some of them) stacked:

My question is: can I assume all the samples are qualitatively identical or do subtle/slight intensity differences in the same bands mean a qualitative difference?

These are all spectra made with a pellet of KBr and I intend a qualitative characterisation to compare with literature, not a quantitative one.


texts: Does the radius of the atom change when an electron is excited?

texts:
The radius of the atom increases when the electron in a hydrogen atom undergoes a transition from the 1s-orbital to a 2p-orbital.

How is this possible? Why does exciting an electron to a higher energy state increase the radius of the atom?


texts: Why does the Co³⁺/Co²⁺ couple have such a high reduction potential?

texts: Cobalt is changing from $\mathrm{(3d)^6}$ to $\mathrm{(3d)^7}$ electronic configuration. What's so stabilizing about that? Just by reduction potentials this couple is more oxidising than hydrogen peroxide and that just sounds amazing and crazy at the same time.


texts:
So I had these two reactions that confused me .. I tried the standard way of balancing it (Putting oxygen number everywhere, +1,+2,-2 etc.) and then go on with it but it didn't work

So anyways here are the 2 reactions:
$$\ce{3 Cu + 8HNO3-> 3Cu(NO3)2 + 2NO + 4H2O}$$
$$\ce{3Ag + 4HNO3 -> 3AgNO3 + NO + 2H2O}$$

I've no idea how do you get those coefficients (numbers).. Please, is there an easy way to do it (perhaps it has to do with electrons added/given? ) and if so - where do I start?


texts:
In graham's law of diffusion most numericals I have seen assumes the formula

$$\frac{r_1}{r_2}=\frac{P_1}{P_2}\sqrt{ \frac {M_2}{M_1}}$$

Where they say $P_1,P_2$  are the partial pressures of the two gases receptively inside the container.But my question is should'nt it be the difference in partial pressures inside and outside the orifice?

Because say if the pressure outside equals pressure inside then the rate of diffusion becomes $0$ .Then graham's law fails in such a case.

Please tell me if I am going wrong.


texts: Why do all medicines require storage temperatures below 25 °C?

texts:
Almost all medicines I buy have storage requirements saying $T\le25^\circ C$.

But do they really spoil at higher temperatures? What if they are stored at e.g. $30^\circ C$, which is common at summertime?


texts:
I have a question about reactions involving hydrogen using catalysts. I'm a layman, so forgive me if my questions seem elementary.

Reacting hydrogen plus oxygen and a flame reacts, unleashing energy (in the form of an explosion) and creating water.

My questions:

Why does it need a "flame or spark "? Is there something unique
about the fire that causes the reaction? Or is it merely the heat of the flame? In other words, if you put hydrogen and oxygen in, say, a
pressurized vessel and added energy in the form of heat (but not a
flame) would it still react and create water? Would it do it without an explosion?
I understand catalysts "speed up" the reaction, or put another way,
reduces the amount of energy required to cause it. I've read that in
this particular reaction ($\ce{H2 + O2}$) copper works as a
catalyst. Is there a way to determine by looking at the chemical
formulas if other catalysts would work as well or better or is it
just trial and error? For example, could you tell if silver would
also act as a catalyst just by looking at the formula? Or would you
need to actually add silver and see for yourself?
When a catalyst is used, is it inexhaustible or does it get "used
up"? If you were using copper to react these two, could you use it forever? If not, is there a way to "recharge" the catalyst?

Thanks in advance, I'm trying to learn about this particular reaction for a project I'm working on ($\ce{H2 + O2}$) but without a formal science background, some of the scientific papers I'm reading are a little hard to grasp.


texts: Wohler synthesis: magnesium cyanate + ammonium chloride?

texts:
Wohler famously produced urea by reacting silver cyanate with ammonium chloride,

AgNCO + NH$_4$Cl $\rightarrow$ (NH$_2$)$_2$CO + AgCl

Naive question: Could this work instead with magnesium cyanate Mg(OCN)$_2$ ?

(I ask because my undergrad chem lab has HCl, Ammonia, and magnesium strips, and I'd like to make some urea, if possible. Not sure how to make magnesium cyanate, but one step at a time...)


texts: Why would a reaction take place in this instance?

texts: This makes little sense to me, both of the electron configurations are d6, and would presumably be low spin - therefore both reactants should be inert, and yet my notes suggest that an electron transfer would occur to form the products Co(II) and Ru(III). Surely this is a less stable arrangement?


texts: How do I prevent oxygen interfering when I prepare a FeCl2 solution from anhydrous FeCl2 powder?

texts:
I have a bottle of anhydrous $\ce{FeCl2}$ powder (from here; it is 98% pure and was kept in a glovebox after opening it for the first time to minimize reactions with oxygen) and want to make this into a solution. I work in a glovebox, but what I have done prior is that I prepared the reagents outside of the glovebox and then put them inside. I let nitrogen gas bubble through water and then add this water to a certain amount of the anhydrous $\ce{FeCl2}$ powder. After this, I put the solution into the glovebox.
However, I get nowhere near to the green color of the $\ce{FeCl2}$ solutions that I find online. My solution has a slight green hue, and after some time I find a little bit of orange precipitate at the bottom of my reagent. So I fear that there is some reaction between the $\ce{FeCl2}$ and $\ce{O2}$. What can I change about my method to prevent this?
The purpose of my research is to produce the mineral tochilinite ($\ce{6Fe_{0.9}S\cdot5[Mg,Fe](OH)_2}$). I mix the $\ce{FeCl2}$ reagent with $\ce{NaOH}$, $\ce{MgCl2}$ and $\ce{Na2S}$. I do not want any $\ce{Fe^{3+}}$ in my $\ce{FeCl2}$ reagent, because it is also not present in the mineral tochilinite. If it is present in the reagent, other minerals might start to form (such as magnetite).


texts: Calculating binding energies for excitated levels in potassium?

texts:
Suppose a laser is used to excite electronic transitions in potassium from the $3p$ orbitals to ones higher than $4s$. When I attempt to use the Bohr model to calculate binding energies, what I obtain for $n\le4$ disagrees significantly with this source, calling into doubt my results for $n>4$. I think it might be possible to use the Rydberg formula, but I'm having trouble finding a working example that computes the right energies; in addition, there is another form, and the two seem inconsistent.  How does one calculate the binding and transition energies in potassium for levels $n>4$? Are the quantum defects for arbitrary elements available online?

What changes here if we're talking not about pure potassium but potassium chloride?


texts: What are the equations giving the molar flow of different molecules linked by a reaction?

texts:
Let consider a steady state CSTR in which occurs the following reaction:

$$\ce{aA + bB \leftrightarrow cC}$$

Notations:

$F_i$ is the molar flow of $i$, $r$ is the rate of reaction, $V$ is the volume, $X$ is the conversion at the end of the reactor, $\nu_i$ is the stoichiometric coefficient of $i$ and $\xi$ is the extent of reaction.

Mass balance:

$$\ce{IN + PROD - CONS = OUT + VAR}$$

Therefore,

$$
\begin{cases}
F_{A,in} + 0 - arV = F_{A,out} \\
F_{B,in} + 0 - brV = F_{B,out} \\
F_{C,in} + crV - 0 = F_{C,out} \\
\end{cases}
$$

As $$\xi = -rV = -X\frac{F_{i,in}}{\nu_i}$$ we have for $\ce{A}$:

$$\begin{alignat}{}
F_{A,out} &= F_{A,in} - arV \\
& = F_{A,in} - a(-\xi) \\
& = F_{A,in} - a\left(X\frac{F_{A,in}}{a}\right) \\
& = \left(1 - X \right)F_{A,in}
\end{alignat}$$

For $B$ with can find as well:

$$F_{B,out} = \left(1 - X \right)F_{B,in} = \frac{b}{a}\left(1 - X \right)F_{A,in}$$

My problem with C:

Now if I follow my calculus for $\ce{C}$, here is what I get:

$$\begin{alignat}{}
F_{C,out} &= F_{C,in} + crV \\
& = F_{C,in} + c(-\xi) \\
& = F_{C,in} + c\left(X\frac{F_{C,in}}{c}\right) \\
& = \left(1 + X \right)F_{C,in}
\end{alignat}$$

Which states that if there is no $C$ at the beginning, there is no $C$ produced at all! Which is wrong. Can you tell me where I am wrong?

NB: I have no clue, which tags fit best for this question.


texts:
Does pyridine or furan have the more shielded proton NMR signals?

I know that both are aromatic, so both have rather deshielded signals due to ring current combining constructively with the applied magnetic field.

However, which would have the more shielded signal? I know that shielded protons have more electron density around them. I guess then the question boils down to whether nitrogen or oxygen is more electron-releasing, as both nitrogen and oxygen have at a lone pair participating in resonance.


texts: In a mixture of NaOH and Na2CO3, why doesn't phenolpthalein change its color until Na2CO3 is half neutralised?

texts:
Let us consider a mixture of $\ce{NaOH}$ and $\ce{Na2CO3}$. Based on what I have understood, double titration works in the below manner :

  Phenolpthalein turns pink when added to the mixture. As $\ce{HCl}$ is added, the pH of the mixture keeps reducing and phenolpthalein becomes colorless when the mixture becomes of a pH less than $8.3$ ie. at a stage when $\ce{NaOH}$ is completely neutralised and $\ce{Na2CO3}$ is half neutralized. Then, we add methyl orange which makes the solution yellow. As we add more $\ce{HCl}$, the pH reduces and hence, methyl orange turns red when the neutralization of $\ce{Na2CO3}$ is complete.

My questions are:

a) When phenolpthalein is added, I have read elsewhere that $\ce{NaOH}$ reacts with $\ce{HCl}$ first. In that case, phenolpthalein should make the solution colorless as $\ce{NaOH}$ neutralizes with $\ce{HCl}$ to form $\ce{NaCl}$ which has a pH of $7$ (not between $8.3$ and $10.5$). Why doesn't phenolpthalein change its color until $\ce{Na2CO3}$ is also half neutralized? Is it because the reactions take place simultaneously?

b) When methyl orange is added, $\ce{NaHCO3}$ is neutralized to $\ce{NaCl}$. But pH range of methyl orange is 3-4.5, but the solution obtained is neutral. How does methyl orange change its color, then?I think it is because of the $\ce{H2CO3}$ ($\ce{H2O + CO2}$) that is formed along with $\ce{NaCl}$, which makes the solution slightly acidic. Is that a correct explanation?


texts: Is there a way to find the mixture type with just the molecular formulas and masses of the solute and solvent?

texts: If you had the molecular formula and molar mass of a solvent and a solute and no other specific information about the two, could one deduce the type of mixture (suspension, colloid, solution) they would create?


texts:
In class, we recently learned about Ionic nomenclature. Specifically, polyatomics and monoatomics. Even though our teacher did a decent job (I guess) of explaining it to us, I'm still very confused.
I have multiply questions:

Question: How would you know what type a compound is when given only the formula?

For example: Our teacher started with $\text{AuCl}$ and wrote down Gold (I) Chloride as the nomenclature. How did he get from $\text{AuCl}$ to Gold (I)?
There are two possibilities: Gold (I) and Gold (III).
Another example: Another example would be $\text{Pb}_3\left(\text C_6\text H_5\text{O}_7\right)$. Which apparently corresponds with Lead (II) Citrate. What does the II inside the parenthesis mean?
And below, I have provided some more examples. Please leave some for me! :P

Examples: Write the formulas for the following compounds:

Copper (II) Chloride

Vandium (III) Selenide

Beryllium Oxide

Potassium Permanganate

Ammonium Nitrate

Tin (II) Sulfite

Chromium (IV) Cyanide

Aluminum Arsenide

I'm lost at this point. Any help and a few suggestions would help a lot!


texts: Pyrrol, furan or thiophene don't have any bond pair electrons free to release which is why they shouldn't be basic, but the lecturer of organic chemistry is saying that they are basic as they react with hydrochloric acid to form salts. Which one of the two explanations are correct?


texts: Why does ionisation energy to remove electrons from the same subshell increases?

texts:
Electrons in the same subshell possesses the same energy.
So why does ionisation energy to remove electrons from the same subshell increases?

For example, $\mathrm{2s^2}$ has two electrons. Since both of them are in the same subshell shouldn't ionisation energy to remove each of them stay the same?


texts: For alkali and lanthanide metals, is there a better liquid barrier to oxidation than mineral oil?

texts:
Most often mineral oil is used to store, protect reactive metals from oxidation. By far the best choice is to hermetically seal the metal in pure argon or some other inert gas, since, although mineral oil tends to slow down the oxidation process, it's still soluble to oxygen and slowly but surely the metal will begin to oxidize.

While argon is a sure thing it requires special equipment, and once sealed you have to break the container to access the metal.

My question - among liquids is there a better choice than mineral oil? A liquid that will not react with the metals, and provide a better barrier to migration of oxygen?


texts: How can I weigh the compound that melts at room temperature?

texts:
I am conducting an organic synthesis experiment involving 2,3,5-tribromothiophene.
The melting point of 2,3,5-tribromothiophene is about 25-28 ℃, so it melts easily during weighing.
Whenever I weigh this compound, it melts soon and wet the weighing paper. So there arises big uncertainty in weight of compound. How can I weigh the compound that melts at room temperature and move it to the reactor with minimum loss? Is there no other way but to weigh as quickly as possible?


texts: Can hemi-acetal rings form under basic conditions?

texts:
I recently encountered a problem on a test.  It was a standard synth problem, "Provide reagents to produce y from x".  The starting material was DHA and the ending molecule was a branched pentose. (I included an image of the solution I came up with).  In my solution I use acetaldehyde under basic conditions to form the pentose.
My question is would pentose form under basic conditions or do I need to acidifying at the end?  Would acidifying just encourage the formation of side products?  Is there some other way to get this pentose as a primary product that I am not thinking of?


texts: Sense of radii quotient to determine coordination number in crystals?

texts:
Every common textbook explains the method of the radii quotient between the cation and anion of a selected salt to determine to coordination number(s) in that salt. For example deduce "Inorganic Chemistry" (Huheey) the coordination number of BeS by following calculation:

Radii quotient $k = \dfrac{r_{\text{cation}}}{r_{\text{anion}}} = \dfrac{59   \text{ pm}}{170 \text{ pm}} \approx 0.35 $

This quotient $k$ indicates a tetrahedral coordination (coordination number for both ions = 6), because $k$ lays between the two limits 0,255 and 0,414 for a energetically favorable tetrahedral coordination (limits are derived through a simple mathematical problem with pythagoras).

Now my actual question or problem with this way to determine the coordination number: The used crystal radii $r_{\text{cation}}$  and $r_{\text{anion}}$ of Be2+ and S2- depend on their coordination; on their coordination number. For example are the crystal radii for Be2+:

Coordination Number = 6: $r_{\text{cation}} = 59 \text{pm}$
Coordination Number = 4: $r_{\text{cation}} = 41 \text{pm}$
Coordination Number = 3: $r_{\text{cation}} = 30 \text{pm}$

The difference between these values are tremendous and change the result of the $k$ calculation above, e.g. if I choose $r_{\text{cation}} = 30 \text{pm}$ then $k=\dfrac{30 \text{ pm}}{170 \text{ pm}} \approx 0.18$ and therefore BeS should be linear coordinated...

In Short: How can we use a method to determine the coordination of a ion in an (simple) ionic structure if the used radii in this method are again depended on the coordination?

Crystal radii data from: http://abulafia.mt.ic.ac.uk/

Edit: I am aware that this method has exceptions and is just simplified (there are many other factors that determine the coordination number)...


texts: Why does the two-electron exchange integral in Hartree-Fock theory have positive values?

texts:
In Section 2.3.6 of Szabo & Ostlund's Modern Quantum Chemistry, the exchange integral has the form of

$$\int \mathrm{d}\mathbf{r}_1\,\mathrm{d}\mathbf{r}_2\, \psi_a^*(\mathbf{r}_1)
\psi_b(\mathbf{r}_1)\frac{1}{r_{12}}
\psi^*_a(\mathbf{r}_2) \psi_b(\mathbf{r}_2)
$$

or $\langle ab|ba\rangle$ in physicists' notation. According to this textbook (and many other books), $\langle ab|ba\rangle$ is positive. The conclusion seems obvious but I just cannot find a proof. Is there any simple reason that $\langle ab|ba\rangle$ must be positive?


texts: Olfactory Receptors Bonding with Organic Material

texts:
How strong is the bond between the olfactory receptors and an organic material, like a perfume?

Is there a chemical that is safe for inhalation that would weaken this bond and prepare the olfactory receptors to receive new scents?

I know that materials like charcoal and zeolite absorb these molecules, but they are carcinogenic when inhaled, so I am searching for an alternative. Any and all advice is greatly appreciated!

Thanks


texts:
Bromine ($\ce{Br2}$) has a dark reddish color. If it reacts with something like benzene, this results in the formation of Bromobenzene and $\ce{HBr}$:
$$\ce{Br2 + C6H6 ->[{Cat.}]C6H5Br + HBr}$$
It can be observed that during this reaction, the color of bromine disappears.
One can thus conclude that $\ce{HBr}$ is colorless. Why is this the case? If we look at the molecules, it seems to me that they are basically the same (speaking in how many electrons there are in each orbital, for example), except for that in $\ce{HBr}$, there is a hydrogen atom instead of another $\ce{Br}$.
So what makes the $\ce{Br2}$ bond "special", so that this molecule can absorb light in the visible spectrum but $\ce{HBr}$ can't?

I think that I have a basic understanding of the quantum mechanic model of an atom (e.g. atomic orbitals and how their energy levels correspond to different wavelengths of light being absorbed). Here are some of my ideas trying to explain the above described question:

In $\ce{Br2}$, both atoms have the same electronegativity, while in $\ce{HBr}$, there is a difference of $\ce{\Delta EN=0.76}$. The only consequence I could imagine from that is that in $\ce{HBr}$, the probability of an electron in the bond to be located closer to the $\ce{Br}$ atom is higher than being close to $\ce{H}$, while in $\ce{Br2}$, the electrons (or rather their probability) is evenly distributed

$\ce{H}$ has an electron configuration $\ce{[1s^1]}$, $\ce{Br}$ has an electron configuration $\ce{[1s^2]\,[2s^2]\,[2p^6]\,[3s^2]\,[3p^6]\,[3d^{10}]\,[4s^2]\,[4p^5]}$. So I would assume that the bond in $\ce{HBr}$ is formed by the overlapping of a $\ce{1s}$ and a $\ce{4p}$ orbital, while in $\ce{Br2}$, two $\ce{4p}$ orbitals overlap. The $\ce{4p}$ orbital has a higher energy level than $\ce{1s}$, so this might be the cause for the different absorption spectrum. However, I am not sure if this is true and how the energy levels behave when two orbitals overlap to form a new one.


texts: Wouldn't radiolabelled phosphorus in DNA break it apart as it disintegrates?

texts:
The Hershey-Chase experiment was designed to prove that DNA is the genetic material in organisms. In this experiment, two batches of viruses were grown in two separate media A and B, with A having an abundance of nutrients involving $\ce{^32_15P}$, and B having a lot of $\ce{^35_16S}$.

Leaving solution B aside, we have $\ce{^32_15P}$ undergo a beta decay:

$$\ce{^32_15P -> ^32_16S + e- + \bar{\nu_e}}$$

This process releases $\pu{1.709 MeV}$ of energy, which is quite sufficient to break apart the phosphodiester linkages.

With all the phosphorus in the viral DNA being radiolabelled, this would very well break apart all the phosphodiester linkages. and give us a soup of sulfur-based nucleosides. In such a case, how come this hasn't affected the virus' mechanism to transfer the DNA to a host cell?


texts: What is wrong with the Aufbau principle that results in so many exceptions?

texts: From what I have observed in the periodic table is that many transition elements do not follow the Aufbau principle. And it's not just the elements like $\ce{Cu}$ and $\ce{Cr}$ that differ from predicted configurations because half-filled and completely filled d-orbitals are more stable, their are many odd exceptions like Nb ($\mathrm{[Kr]}4d^4\,5s^1$), Pd ($\mathrm{[Kr]}4d^{10}\,5s^0$). What reasons lead to such configurations?


texts: What is the difference between a chemical state and just a combination?

texts: I don't think a combination also can be called a "state" i.e. that the chemical state of vapour or solid would be just a combination. When I read Wikipedia about "chemical state" it refers to just a combination. But AFAIK, an entity that has just combination does not have a state. So how do we know what is a state and what is just a combination?


texts: What is the value for the reverse reaction?

texts:
My question deals with the reaction $\ce{2NO(g) + O2(g) -> 2NO2(g)}$ with $K_c = 1752$.

This is what I have so far; $K_c$= products over reactants, so is the reverse reaction reactants over products to find the answer
Such as
$$1752 = \frac{[\ce{NO2}]^2}{[\ce{NO}]^2[\ce{O2}]}$$
So then does the answer become
$$1752 = \frac{[x]^2}{[x]^2[x]}$$


texts: Pauling's equation on the relationship between Electronegativity and Percentage Ionic Character

texts:
In Paulings eqn:

$$ \%~\ce{ionic~character} = \left[ 1−e^{−(Δχ/2)^2}\right] \times 100$$

What is $e$?

I for the love of me can't find it anywhere


texts: Which characteristics of the compound affect the number of theoretical plates in a GC experiment?

texts:
Some days ago, I tried for the first time a chromatography machine.
The data I collected are the following:
$$
\begin{array}{lrrr}
\hline
\text{Compound}                 & t_\mathrm{R}/\pu{min} & w/\pu{min} & N     \\
\hline
\text{Benzene}                  & 2.325                 & 0.047      & 39153 \\
\text{Toluene}                  & 2.712                 & 0.067      & 26214 \\
\text{Chlorobenzene}            & 3.690                  & 0.099      & 22228 \\
\textit{p}\text{-Chlorotoluene} & 4.332                 & 0.106      & 26723 \\
\hline
\end{array}
$$
I know the relationship between retention time $t_\mathrm{R},$ peak width $w$ and theoretical plates $N.$
Known the different properties, boiling points, polarities, or shapes of the molecules involved, is there a way to predict which molecule will yield an higher number of theoretical plates?
Which characteristics of the molecules affect the different number of plates for each molecule?


texts: Name of round piece of glassware with thin neck?

texts: Found in the lab, it looks like a round bottom flask with an extremely thin neck. Effectively a glass sphere about 60 mm in diameter with what looks like a capillary tube as the neck. Not sure whether it is a standard COTS item or custom glass.


texts: Why are tertiary amines less basic than secondary and primary amines in water than when vapourised?

texts:
In gaseous state:

$$\ce{(CH3)3N} > \ce{(CH3)2NH} > \ce{CH3NH2} > \ce{NH3}$$

However, when dissolved in water:

$$\ce{(CH3)2NH} > \ce{CH3NH2} > \ce{(CH3)3N} > \ce{NH3}$$

My notes mentioned the reason for this is because of the increased steric hindrance from the greater number of alkyl group which makes the lone pair of electrons on the N atom less available. But, if this is the case, why doesn't steric hindrance affect the basicity of tertiary amines when in a gaseous state?

After some research, I found that the conjugate acid of an amine can be stabilised by solvation. But, shouldn't the stabilisation be the same, because of the attraction of electronegative O in a water molecule to the positive charge on $\ce{N}$ in an ammonium salt? (can ammonium salts still be stabilised by hydrogen bonding? I thought ions don't form hydrogen bonds with water, they form ion-dipole attractions)

Unless the effect of steric hindrance comes in here, where the alkyl groups reduce the strength of the ion-dipole attraction between the ammonium ion and thus the stability?

I'm really confused how everything links up; appreciate it if someone can kind of clear this up.


texts: Why do we still use the 'P' subscript in a thermodynamic derivative such as (dH/dT)P?

texts:
Consider the following thermodynamic derivative:

$$
\left(\frac{\partial H}{\partial T}\right)_P
$$

Taking the partial derivative w.r.t. $T$ means that all other variables are held constant. Why do we still write it with a subscript like $P$ or $V$?


texts: Entropies of Solvation for Chlorate and Nitrate Anions

texts: Can anyone find any data on the entropies of solvation for these two anions in water solution? I can't find any.


texts:
I've always heard that different isotopes of the same element have exactly the same chemical  properties.

But for example, I've read that some compounds which have hydrogen atoms interchanged by deuterium become odorless (this is one of the arguments for the vibrational theory of olfaction).

  A 2001 study by Haffenden et al. showed humans able to distinguish benzaldehyde from its deuterated version. In addition, tests with animals have shown fish and insects able to distinguish isotopes by smell

So, are there any situations in which  neutrons do matter (besides nuclear decays)?

Addendum 2013/10/28

Another curious effect is that water is slightly blue, due to vibration. But heavy water is not.

  Heavy water is colorless because all of its corresponding vibrational transitions are shifted to lower energy by the increase in isotope mass. For example the H2O band at 760 nm is shifted to approximately 1000 nm in D2O.

(Left: tube if filled with (light) water. Right: empty tube.)


texts: Separating gold and silver from gold foil using hydrochloric acid and hydrogen peroxide

texts: I used  $\ce{HCl}$ and $\ce{H2O2}$ to recover gold foils by dissolving all other metals. My solution I assume contains a large amount of silver. How do I drop the silver out of the  $\ce{HCl}$  and peroxide solution.)


texts: What is the mechanism of action of anaesthetics?

texts:
A range of very different compounds are used in medicine as anaesthetics. They don't seem to have much in common chemically but they all seem to keep people asleep while medics are doing nasty things to them.

Inhaled anaesthetics include a variety of fluorocarbon gases such as halothane and sevoflurane plus barbiturates like thiopental, oddballs like propofol and even xenon:

What do these heterogeneous compounds have in common and how do they work?


texts:
Calculate the partial pressure of $\ce{NO2}$.

$$p_{\ce{N2}}/p_{\ce{O2}}=5$$

$$\ce{N2(g) + O2(g) <=> 2NO(g)}$$

Let’s assume $K=0.1$

$$K= \frac{p_{\ce{NO}}^2}{p_{\ce{O2}}\cdot p_{\ce{N2}}}$$

$$K= \frac{p_{\ce{NO}}^2}{p_{\ce{O2}}\cdot p_{\ce{O2}}\cdot5}$$

But how do I proceed?


texts: Synthesis of 2-phenoxybutanal from but-1-yne

texts: How can I convert 1-butyne to 2-phenoxybutanal as shown above? I thought of using a hydroboration-oxidation sequence to introduce the carbonyl group, but I do not know how to add the phenoxy substituent.


texts: Acidity order checking for α-furoic acid and acetic acid

texts: α-Furoic acid's conjugate base is aromatic and hence is more stable. Then why acetic acid is more acidic than α-furoic acid?


texts: Effects of inert gas on heterogenous equilibrium

texts: What is the effect of the presence of an inert gas on a reversible reaction that was in more than one phase, such as a decomposition reaction?  If a solid or liquid or compound in aqueous solution decomposed in a reversible reaction, and one or more of the products was a gas, would the equilibrium shift if an inert gas was added and volume and temperature were kept constant (so total pressure would increase)?


texts: Does aluminium foil have an odour/gas off?

texts:
I have used some aluminium foil to cover some windows and I notice a light smell in my small flat. I could be mistaken and it could something as I've been moving things around but this leads me to wonder does aluminium foil have an odour/gas off?

I notice it sticks to things as well so might this be an added solvent or what property of the foil gives it this characteristic?


texts: Order of features in chemical descriptors

texts:
ECFP are small-molecule descriptors, which are usually represented as a bit vector. I wonder if order of elements of this vector matters, in other words, if this vector encodes any positional information. I couldn't find this information in the papers.

Thank you


texts: Characterization of products of non-stoichiometric combustion

texts:
To give some background, I'm looking at this from an aerospace standpoint as to the calculation of the efficiency of a propellant reaction at a given oxidizer-fuel ratio. That efficiency is a prerequisite to obtaining other results such as the adiabatic flame temperature, the specific impulse ($I_{sp}$) and other such data.

How is it that the relative abundances of products can be obtained from a non-stoichiometric combustion in an analytic manner (i.e. without needing to obtain empirical data)? This is particularly important because rocket engines rarely run stoichiometric, due to exhaust considerastions.

From the Wikipedia article on combustion, it shows that incomplete combustion results in primarily carbon dioxide, carbon monoxide, water and elemental hydrogen gas. However, it also states that:

  For stoichiometric (complete) combustion, $z = x + ¼y$. When $z$ falls below roughly 50% of the stoichiometric value, $\ce{CH4}$ can become an important combustion product; when $z$ falls below roughly 35% of the stoichiometric value, elemental carbon may become stable.

This makes sense, as anyone who has left the barrel of a lit Bunsen burner shut has seen the sooty smoke it produces; but is there a manner in which these products may be analytically identified (and quantified)?

To cover all bases, I've had some experience with the use of NASA's CEA program, and it appears to have some ability to calculate thermodynamic parameters of propellants that aren't given as choices (i.e. RP-1, $\ce{H2}$, etc.). I've read the manual on its theory of operation, but I'd like a more gentle introduction to the underlying behavior, if at all possible.


texts: Representation of bromelain molecule in two dimensional diagram

texts:
If I'm not wrong, I learned in 2011 introduction to neuropsychology course that all enzymes are proteins.

As far as I know, any protein, not even the smallest of the TAL group (which I understand to be the smallest currently known protein group), can be represented on a common-size two dimensional diagram (say, A4 page size) simply because it's too big in comparison to other molecules (such as methylcobalamin).

If bromelain is an enzyme which is larger than, for example, TAL proteins, how come it is represented on a common-size two dimensional diagram in PubChem?


texts: Arranging the phenol derivative in decreasing order of acidity

texts:
I am facing difficulty in the following problem.

What is the decreasing order of acidity of the following phenol derivatives?

In my view benzene-1,2-diol 1 should be most acidic because $-\ce{OH}$ is a strong $-I$ group thereby it will stabilise the negative charge on oxygen formed after removal of a proton.
$\ce{OCH3}$ is a $+R$ and $-I$ group. Near the carbanion $-I$ effect should be more effective. Hence the second most acidic should be 2-methoxyphenol 2. However the answer key gives it as 4-methoxyphenol 3.


texts: In a Koppers-Totzek reactor, why do I get CO and H₂ instead of CO₂ and H₂O?

texts:
A Koppers-Totzek reactor (there seems to be only a German Wikipedia page) is an entrained flow gasifier that blows coal dust, oxygen and water (as steam, of course) into a burning chamber where the coal burns at about 1600 °C. The output contains around 60% $\ce{CO}$ and 33% $\ce{H2}$, plus some $\ce{CO2}$ and (very little) $\ce{CH4}$.

When burning coal, I would expect $\ce{CO2}$ and $\ce{H2O}$ as output, is the reactor simply providing too little oxygen, or is there something about the process that produces the output observed?


texts: What does a square mean in a chemical formula?

texts:
We find in the book Minerals and their Localities by Jan H Bernard and Jaroslav Hyrsl   several chemical formulas containing a square. What does this square means? An example: Franciscanite $\ce{Mn3 (V,\square)(O,OH)3 (SiO4)}$

Thanks for your answer for  I have been  looking for answer for a long time.


texts: Why does hydrogen phosphate act as a base?

texts:
Let's look at question c:

  a) Write a balanced equation for the reaction.
  $$\ce{2 NaOH + H3PO4 -> Na2HPO4 + 2 H2O (l)}$$

  b) When some crystals of $\ce{Na2HPO4}$ were dissolved in water, the $\mathrm{pH}$ of the resulting solution was found to be $9.5$. Calculate the hydrogen ion concentration of this solution.
  $$[\ce{H+}] = 10^\mathrm{-pH}\, ;\qquad [\ce{H+}] = 10^{-9.5} = \pu{3.2e-10 mol L-1}$$

  c) Write an equation for the reaction of the $\ce{HPO4^2-}$ ion with water to account for the measured $\mathrm{pH}$.
  $$\ce{HPO4^2- + H2O (l) <=> H2PO4- + OH-}$$

So, I'm a bit confused with what's happening. It seems that water is acting as an acid in this reaction, and donating protons to the ion. Can someone just elaborate on this whole process please because I'm not really sure what is happening. Why is it $\ce{HPO}$ and not $\ce{H2PO}$ or $\ce{H3PO}$ (as is in the original equation?) Is it a step wise process and only one step included?


texts: What's the relation between molarity and molality?

texts:
I am trying to derive the relation between the molarity and molality of a solution

Mole concept $\displaystyle n = \frac{M'}{M''}$

Here, ($n$) stands for number of moles
$\ce{(M^{'})}$ stands for mass of substance in gram
$\ce{(M^{''})}$ stands for molecular/atomic mass of substance

Let $V_{\text{sol}}= $ volume of solution
Molarity (M) $= n/V_{\text{sol}}$

The above equation of molarity ($M$) shows the concentration of solution of substance, i.e. ($M$) is the ratio of number of moles ($n$) with respect to it's volume ($V_{\text{sol}}$)

let $W$ = mass of solvent in kilogram
molality $(m) = n/W$

The above equation of molality ($m$) shows the concentration of solution of substance
i.e. ($m$) is the ratio of number of moles ($n$) with respect to mass of it's solvent ($W$)

What is the relation between molarity ($M$) and molality ($m$)?

Molarity ($M$) = $n$/$V_{\text{sol}}$
Molality ($m$) = $n$/$W$

I'm confused on how to relate the $W$ with $V_{\text{sol}}$.


texts: Why are hybrid orbitals more efficient at overlapping?

texts:
What is the reason for considering that hybrid orbitals provide more effective overlapping resulting in formation of stronger bonds?

Will this reasoning be correct that the hybrid orbitals have larger and smaller lobes than pure orbitals?


texts: What is the empirical formula for kerosene?

texts:
Kerosene is a blend of hydrocarbons, so it doesn't have one chemical formula. But I'd like to find an (approximate) empirical formula giving the ratios carbon and hydrogen.

I haven't found anything online, and beggars can't be choosers. My actual interest is in RP-1. There is a NIST document (archive) on its thermophysical properties which gives a spectroscopic breakdown on pages 29–32 showing that even this highly refined kerosene is mind-bogglingly complex chemically.


texts: Why doesn't beryllium, an elemental solid, obey Dulong and Petit's law?

texts: Beryllium has a molar heat capacity of $\pu{17.7 J mol-1 K-1},$ which is quite far from the $\pu{25 J mol-1 K-1}$ as predicted by Dulong and Petit's law. What is the reason for this discrepancy?


texts: Is it possible to oxidize beryllium metal around NTP or not?

texts:
Perhaps this seems like a really simplistic question to many of you, but I’ve read too many conflicting answers at this point.

Simply put, most articles I’ve read have insisted that it isn’t possible to ignite pure beryllium below temperatures of about 1000 to 1200 Celsius. However, the explanation behind this usually has something to do with an oxide layer forming on the outside of the metal that prevents oxidation of the metal atoms that aren’t on the surface anywhere near NTP (20 C, 1 atm). This logic doesn’t track for me, as it clearly suggests that oxidation at NTP can occur in an attempt to explain why it can’t.

I guess my question is, if you were to take a sizable chunk of beryllium metal, grind it up to an extremely fine powder — or rather, since we’re thinking theoretically, pound it out into a single-atom-wide sheet — and then expose it to oxygen gas at a pressure of 1 atm and a temperature of 20 C, how violently would said metal powder/sheet react?

To me, all literature on the subject seems to imply that it reacts at an imperceptibly slow rate like an iron fence rusting, although even iron oxidation becomes noticeable with fine powders (e.g. in single-use handwarmers). Is this true, or would something more noteworthy occur?


texts: Why can't bicyclic structures undergo E2 elimination?

texts: Bicyclic structures like norbornane don't undergo E2 eliminations, but why is this the case? I understand that it can't do E1 as it can't form a stable carbocation (the bridgehead carbons that is) but I don't see the issue for E2. Can you explain?


texts: How to calculate the equilibrium pressure when ammonia and hydrogen gasses react in a closed system?

texts:
There is a container that has a volume of $5~\mathrm{L}$ on one side and $3~\mathrm{L}$ on the other and is separated in the middle. There are $2~\mathrm{mol}$ of $\ce{N2}$ on one side at $0~^\circ\mathrm{C}$ and $4~\mathrm{mol}$ of $\ce{H2}$ on the other at $0~^\circ\mathrm{C}$. When the valve is turned and the gases react, what will the total pressure be?

The balanced reaction is $$\ce{N2 + 3H2 <=> 2NH3}$$
My thinking was that the reaction occurs at STP so the pressure would stay at 1  atm?
Or that you could use
\begin{align}
pV &= nRT\\
p(8~\mathrm{L}) &=6(.082)(273.15)\\
p &= 0.06
\end{align}
The $8~\mathrm{L}$ comes from adding the two volumes, and the 6 from adding the number moles together.


texts: How lyophilic colloids reduce surface tension?

texts:
Its given in my textbook that surface tension of lyophilic/hydrophilic solution is lower than water.
But my intuition says,since in lyophilic solution the interaction between a lyophilic colloid and water molecules would be more than it would be in between two water molecules,the surface tension would increase. But my textbook says otherwise. What am I missing?


texts: Comparing energies of isoelectronic species, but one protonated

texts:
Let's say we have the following reaction:

$$\ce{RH -> R- + H+}$$

By modelling it using quantum chemical calculations in the gas phase I would make calculations for both $\ce{RH}$ and $\ce{R-}$, but $\ce{H+}$ has no electrons.

On the other hand, $\ce{RH}$ and $\ce{R-}$ are isoelectronic and zero energy is assigned for infinitely separated particles.
I have a gut feeling that the energetics of $\ce{RH}$ and $\ce{R-}$ can't be compared directly in this case, but I can't think of a good argument for this.
So, can I compare them? Why or why not?


texts:
I really see no relation between the terms microcosmic and the salt's structural formula, $\ce{Na(NH4)HPO4.4H2O}$.

Devoting sufficient time on Google didn't help at all.

Information about the name of this compound is what I'm searching for, thanks in advance for sharing.


texts: CIP Rules - How to deal with a double bonded nitrogen?

texts:
If a substituent were to exist, how will one deal with the doubly bonded nitrogen? In the tree will the nitrogen with the double bond have (C,C) or (C,C,C) or (C,C,lone pair)?
I could not find this case on the CIP Wikipedia.

Also if it were (C,C), then how would one compare the priority of this with say (C,C,C)?

It would be helpful if you could draw the complete hierarchical digraph.

Here is my shot at it:


texts: Quantify the effectiveness of baseline correction in Raman spectra

texts:
I've produced several thousand Raman spectra using hyperspectral imaging techniques. These suffer from significant fluorescent interference which produces a curved, sloped baseline.
Using Matlab, I have attempted several baseline subtraction techniques but I can't say quantitatively which is performing best - beyond a visual inspection I'm not sure how to compare them.

Is there any quantitative way of assessing the performance of a baseline subtraction? Or is visual inspection really the best we can do?

Thanks for taking the time to consider this.

Edit:
I've added an example spectrum along with one with a corrected baseline.

Thank you for your suggestions as regards methods for baseline correction, however, I have already used several different methods successfully. My intention was to discover if there was a way of measuring the performance of various techniques in order to asses which is the most effective.

Thanks again for your consideration.

Edit 2:
I just wish to clarify that I am not looking for methods for baseline correction. I have used several which have given me varying results - these include polynomial fitting, piece wise fitting, ModPoly, subtraction of iteratively smoothed savitzky-golay baselines, and WPLS.
What I'm looking for is a way to quantify their performance, is there any metric that can be used to do this?


texts: Understanding gas stoichiometry for the reaction of xenon and fluorine

texts:
A $\pu{20.0 L}$ nickel container was charged with $\pu{0.500 atm}$ of xenon gas and $\pu{1.50 atm}$ of fluorine gas at $\pu{400 ^{\circ}C}$. The xenon and fluorine react to form xenon tetrafluoride. What mass of xenon tetrafluoride can be produced assuming $100\%$ yield?

Attempt at solution: From the description, the reaction can be written as
$$\ce{Xe + 2F2 -> XeF4}.$$
I first calculated the amount of substance of $\ce{Xe}$ using the ideal gas law:
$$n(\ce{Xe}) = \frac{pV}{RT} = \frac{\pu{0.5 atm} \cdot \pu{20 L}}{0.08206 \cdot \pu{673 K}} = \pu{0.18 mol}$$
Doing the same for fluorine gives:
$$n(\ce{F2}) = \frac{\pu{1.5 atm} \cdot \pu{20 L}}{0.08206 \cdot \pu{673 K}} = \pu{0.54 mol}$$
Then, for every mole of $\ce{Xe}$ we need two moles of $\ce{F2}$. Since we have more than $2 \cdot \pu{0.18 mol} = \pu{0.36 mol}$ of fluorine, xenon is the limiting reactant. The molar mass of $\ce{XeF4}$ is $207.1\,\mathrm{g/mol}$.
So now I would just do:
\begin{align}
n(\ce{XeF4}) M(\ce{XeF4}) &= m(\ce{XeF4})\\
\pu{0.18 mol}  \times \pu{207.1 g mol-1}  &= \pu{37.278 g}
\end{align}
However, the answer at the back of my textbook says it should be $\pu{37.5 g}$. So did I make a mistake somewhere or is this just a roundoff-error?


texts:
This question may sound silly.
What actually I understood from this experiment is that the positively charged nucleus which is in the center is responsible for the bending and reflection of the alpha rays.Here is my question:Why cant there be any small holes in the gold foil which might have caused this kind of behavior?


texts: Chemical Structure of PLA soaked in Ethyl acetate

texts:
I am trying to find a way to separate my PLA samples and ABS samples. Both of these are 3D printing plastics (Polylactic acid and Acrylonitrile butadiene styrene)

Last night I've observed:

When soaked in Ethyl Acetate:

ABS disintegrates in about an hour,
PLA loses "fancy" properties, ( such as green/yellow color-changing filament, went blue. )
All PLA, fancy or standard, turns very flexible.

I would say this could be a good start for my process, as the ABS is separated from the PLA, but the PLA has changed now to a fairly unusable form, (the ABS especially so)

How can I understand this "flexible PLA" and the solution? I can see that the PLA has been chemically altered, but how? and can it be corrected? What happened to the Ethyl Acetate and the ABS?

I'm still quite noobish in chemistry, so I'm happy for anyone to throw a book at me or where I should start to learn about this.

In the meantime, I'm planning to make more flexible samples of PLA to put into the dehydrator later this week in a vain effort to see if that might "evaporate" and correct it, but I'm hoping someone would be able to give me a bit of a leg-up on understanding this chemical change and how to account for it. The end result is for the PLA to be grounded and melted into usable forms.

The plastics are visibly similar, which makes it a bit difficult to separate by eye.


texts: I see that in most textbooks Alkanide shifts are shown as concerted mechanisms, but Hydride shifts are not. Why is this done? Shouldn't the rearrangement be concerted when the carbocation formed is primary and not concerted when the carbocation formed is secondary, regardless of whether or not it is an alkanide or hydride shift? Thank you.


texts: Receiving milk for working in harmful environment

texts:
I just got a job in a chemical/biological lab (post-Soviet Country). Chemists here receive milk for "harmfulness of the work" (i .e. their work involves working with all kind of substances/reactives). I'm not a chemist; I do their analysis. The tradition of receiving 0.5 liters of milk a day comes all the way from the Soviet Era. I found this question here: Does milk drinking prevent long-term chemical poisoning?

However, I would like to know if milk is not that great for preventing chemical poisoning (as seen from the accepted answer), why is there still such a tradition of giving milk? And why did this tradition appear in the first place? And do people working in chemistry labs in other countries also get milk? (I'm not sure, but I think in UK they do.)


texts: Which set of reactants is better for preparation of 1-methoxy-4-nitrobenzene?

texts:
I've got two set of reactants:

4-nitrobromobenzene + sodium methoxide
sodium 4-nitrophenoxide + bromomethane

I've got to tell which reaction is more preferable among these two.

The first reaction takes place through nucleophilic addition of methoxide on the ring followed by elimination of bromine. I've been taught that such reactions take place under drastic conditions, but the presence of an electron withdrawing group at ortho and para position increases the reactivity, so the presence of $\ce{NO2}$ group should increase the reactivity .

The second reaction takes place by SN2 mechanism, where bromomethane is attacked by the nitrophenoxide ion. This reaction "seems" to be better than the first. (Is it?)

Hence, my attempt is that the second reaction should be more favourable than the first since the first reaction should take place under more drastic conditions than the second.

Am I right? Or does the presence of $\ce{NO2}$ group increase the reactivity so much that it is comparable to the second reaction or maybe better?


texts:
I was asked to solve this problem, and the answer key shows this:

I'm not sure what's going on here, but it looks like some sort of a rearrangement and reduction. Is it an internal reaction between the ether and the alkene?


texts:
My book says that to favour a reaction by SN1 mechanism we need to use a polar protic solvent and a polar aprotic solvent in a reaction by SN2.
* My Prior Knowledge:*

  There are two types of polar sovents : Polar Protic Solvents contain a hydrogen bonded to a highly electronegative atom. They can solvate both positively and negatively charged species. On the other hand Polar Aprotic Solvents can only solvate positively charged species to an appreciable extent as there is no hydrogen bonding.

A question which arises now is that why should we use a Polar Aprotic Solvent in an SN2 reaction. The leaving group (which usually is negatively charged) needs to be stabilized as well. Wouldn't it be perfectly fine if I used a Polar Protic Solvent? If this is fine then why does presence of Polar Protic Solvent favor SN1 over SN2?
Also I asked this question on SE a while back. I am looking for a more satisfactory answer apart from the ones given. here


texts: Predicting electronic geometry, observable geometry, and hybridization for any atom in a molecule

texts:
Can someone please explain the intuition around the answers to this problem:

I'm finding it very confusing because it seems like you have to nitpick between two resonance structures to get the desired results. Do we just always look for the "lowest" possible VSEPR in any resonance structure? Why isn't the observable geometry for "X" linear instead of none?


texts: What is the Chemical Compound that has a NFPA 704 (Fire Diamond) of 2-2-1-ox?

texts:
I recently saw this fire diamond configuration of:

2 - Flammability;
2 - Health;
1 - Reactivity;
OX - Extra Information

I have been attempting to find a database of terms, but after turning up with nothing, and seeing a similar answer about fire diamonds answered here, I posted this question.

I would be thankful if someone happened to know what compound that this fire diamond is labeled to.


texts: On which side is the intermediate carbocation formed during acid-catalyzed opening of epoxide?

texts:
I found an organic chemistry question which asked the major product of the following reaction -

The mechanism for the same in the answer was -

My questions regarding this are as follows -

The molecule has two oxygen atoms, one as an epoxide and the other as ketone. How do we decide which oxygen atom accepts the proton? Seeing the mechanism provided in the answer, I reasoned that the epoxide oxygen is sp3 hybridized, hence less electronegative than the ketone oxygen, which is sp2 hybridized. Hence as the less electronegative atom it donates its lone pair to the proton. Am I correct? If not, what is the real reason?

Acid-catalyzed opening of epoxide follows SN1 mechanism, which implies more stable carbocation must be formed. In the given mechanism, however, the carbocation is formed on the right side, where the carbonyl group exerts -I effect and destabilizes the carbocation. I could not make sense of this.

Are there any specific rules as to which site is attacked by the proton if multiple nucleophilic sites are present in the molecule? Also, is my reasoning in (2) correct?
I am also open to the fact that the given mechanism in the image may be wrong, in which case, I would also like to know the correct mechanism and product.


texts: Why there is a temperature change in adiabatic process?

texts: I am learning the topic thermodynamics and I came to know that in an adiabatic process the heat of the system remains constant. So is it a hard and fast rule that temperature will  change in an adiabatic process?


texts:
I read in many MSDS that Isopropyl alcohol tends to form peroxides (by reacting to air OR light) which may explode when they reach a given concentration.

For example: http://nj.gov/health/eoh/rtkweb/documents/fs/1076.pdf or http://www.hvchemical.com/msds/isal-70.htm as well as many others.

I own a few liters of isopropyl alcohol (a few bottles) and I'm getting concerned.
It came in standard transparent (polypropylene I suppose) bottles with a plastic bag wrapped around it (I suppose to prevent contact with air). I only keep one bottle ready to use, all the others are as when I bought them (with plastic bag wrapped around it), stored in a relatively cool (<= 25°C) dark area of my house.

This is at home and I couldn't find any fire resistant storage cabinet in my area.

Now, I'm not sure if I understand the datasheet correctly, but as far as I understood the problem lies with the opened bottle (which I open and close regularly) and not with the air-tight never opened other bottles, right?
Therefore a simple solution may be to say: after one year I empty the opened bottle, trash it away and buy another one. Should this be enough?


texts: is the given rearrangement possible {major product}? from cyclo butane derivative to cyclohexane derivative.


texts:
I was asked to use direct differentiation of "H = U + pV" to find a relationship between:

$$ \left(\frac{\partial H}{\partial U}\right)_{\!P}$$   and   $$\left(\frac{\partial U}{\partial V}\right)_{\!P} $$

So my first step was to take a differential of the equation twice, once in terms of U and once in terms of V:

$$ \left(\frac{\partial}{\partial U}H\right)_{\!P}=\left(\frac{\partial}{\partial U}(U +PV)\right)_{\!P}\rightarrow\left(\frac{\partial H}{\partial U}\right)_{\!P}= 1 + P\left(\frac{\partial V}{\partial U}\right)_{\!P}$$
and

$$ \left(\frac{\partial}{\partial V}H\right)_{\!P}=\left(\frac{\partial}{\partial V}(U +PV)\right)_{\!P}\rightarrow\left(\frac{\partial H}{\partial V}\right)_{\!P}= \left(\frac{\partial U}{\partial V}\right)_{\!P} + P$$

When I tried to substitute one equation into the other, they would simply end up all canceling out. Is there another way?


texts: Why can anthracene, but not phenanthrene, take part in Diels–Alder reactions?

texts: Both anthracene and phenanthrene seem to be structurally similar, with three aromatic rings. The middle rings in particular seem to be similarly activated towards cycloadditions.


texts: Plot of Arrhenius Equation with temperature

texts:
I saw the following plot of the Arrhenius Equation on Wikipedia (cc-by Zivilverteidigung and Matthias M.).

It is a concave upwards graph, but according to the equation
$$k= A \mathrm e^\frac{-E_\mathrm a}{RT},$$
 it is evident that the graph is of the form
$$y= \mathrm e^\frac{-1}{x}.$$

I believe that this should have been the graph (please disregard the negative side of the $x$ axis). It is a concave downwards curve. Why is there a discrepancy?
This maybe also suitable in Mathematics.se, but I have a gut feeling that the solution to this lies in Chemistry and not maths.


texts: Can terminal enols be reduced by using LiAlH4?

texts:
According to the solution given in my textbook, no reaction takes place in this case.

But I am not quite sure about it. I feel that the enol can easily tautomerize to aldehyde and we know that aldehydes are reduced by $\ce{LiAlH4}$ to give alcohols.

So, will the above reaction take place? What will be the final product after reduction occurs?


texts: Does grignard reagent react with oxygen?

texts:
Does this reaction actually take place -

$$\ce{C2H5MgCl + O2 ->[H2O] C2H5OH}$$

I never saw this kind of a reaction. I thought that grignard reagent might take a proton from water and just form ethane.


texts: Is there pure iron in nature, would that be not become Iron Oxide (rust) immediately because of the humidity? How do we produce iron ore/dust on the lab/industry?


texts: What is the volume of the produced SO2 gas at STP?

texts:
In a electricity producing plant $3.1\times10^7\ \mathrm{kg}$ coal with $2.4\ \%$ rhombic sulfur is burnt every year. What is the volume of the produced $\ce{SO2}$ gas at STP?

My effort  for solving this answer :

In one day how much sulfur is burnt. Then I wrote the equation

$$\ce{S + O2 -> SO2}$$

With the unitary method I tried but I am confused from where to start, how to start? Please give me a hint how to start the answer.


texts:
I've been researching sodium polyacrylate, which normally comes as those "aqua gems" for plants, or fake snow. Specifically, I've been hoping to find information on molding, casting, or otherwise giving shape to the material - nothing terribly complex, just things like simple stars for example (while hoping no one mistakes them for Jell-o jigglers).

So far, I've only been able to determine that sodium polyacrylate is not a thermoplastic, so the obvious solution won't work. I heard from one source that those toys that grow in water may be made of the same stuff combined with another polymer, but couldn't get any further leads on the subject.

So the question is, what solutions are available for giving sodium polyacrylate a defined shape, while keeping most of its absorption/growth properties?


texts: Why is cyclooctateraene shaped like a "tub" rather than a "chair"?

texts:
I understand that for cyclooctatetraene (COT) to "escape" the horrible prospect of becoming an anti-aromatic molecule, it must adopt a non-planar conformation.

The widely touted conformation of COT is said to be "tub" shaped. My sources (random links Google threw up) also concur on this particular "tub" conformation.

But why isn't it "chair" shaped instead?

Going along the same line of cyclohexane (non-aromatic), wouldn't a "chair" conformation reduce (even if it's a little bit) the steric repulsions due to crowding of hydrogens atoms on one side/face of the molecule?

Or even if "avoiding steric issues" isn't really the big idea here, then I could re-phrase my question as:

What stops COT from assuming a "chair" shaped structure?

The "chair" structure that I have in mind for COT is something like this:

(I don't have access to a decent enough organic chemistry sketcher to have this drawn any better, sorry.)