texts:
Consider the following question:

The enthalpy of vapour is $10\ \mathrm{kcal}/\mathrm{mol}$ higher
than liquid at $350\ \mathrm{K}$ and $2\ \mathrm{atm}$. Under given
conditions, the difference in internal energy of vapour and liquid
will be:
(a) $10700\ \mathrm{cal}$
(b) $-9300\ \mathrm{cal}$
(c) $9300\ \mathrm{cal}$
(d) $-10700\ \mathrm{cal}$

My solution is as follows:
Let the internal energy of the liquid be $U_\mathrm L$ and that of vapor be $U_\mathrm G$. We are required to calculate $U_\mathrm G - U_\mathrm L$. As per the question,
$\because H_\mathrm G = U_\mathrm G + W$, where $H_\mathrm G$ is enthalpy of vapor.
$10000 + U_\mathrm L = U_\mathrm G + W$
Where $W$ is the work done due to the expansion of vapor as the liquid changes state. The magnitude of work done $|W| = \Delta n_\mathrm gRT = 1 \times 2 \times 350 = 700\ \mathrm{cal}$.
Now the real question starts, what is the sign of $W$? As per the IUPAC convention, work of expansion is negative, hence $W = -700\ \mathrm{cal}$. So our answer will come out to be,
$10000 + U_\mathrm L = U_\mathrm G - 700$
$\implies 10000 + 700 = U_\mathrm G - U_\mathrm L$
$\therefore U_\mathrm G - U_\mathrm L = 10700\ \mathrm{cal}$
But the terse solution given to this question is:

As per the solution $W = +700\ \mathrm{cal}$, i.e. they have considered the work of expansion to be positive.
Where are we wrong? Or are we right?


texts:
The characteristic wavelength of ZnO is supposed to be ~380 nm. However, in this article1, the peak has been blue-shifted to 214 nm. This is quite similar to my sample where the peak is at 200 nm.
In the article it is said that:

  the blue shift may be due to the transition of electrons from the inner shell of copper to the outermost shell as time passes. It is possible that, due to aggregation and agglomeration, particle size increases and material settled down on the bottom of the container causing decrease in absorbance.

Could someone explain what this means?

Also, I did a UV-dr on the sample and it gives me a peak at 380 nm.

1: Structural and Optical Characterization of ZnO Nanoparticles Synthesized by Microemulsion Route. International Letters of Chemistry, Physics and Astronomy 2013, 14, 26-36.


texts: Why does cyclobutadieneiron tricarbonyl behave aromatically?

texts:
It is said that $\ce{(\eta^4-C4H4)Fe(CO)3}$ can undergo electrophilic substitution reactions. Therefore, it displays aromaticity.
For the iron atom, it has $8$ electrons in its outer shell initially and it receives $6$ electrons from three carbonyls. It achieves the stable state of $18e$ after bonding with cyclobutadiene. Therefore, the oxidation state of iron should be zero, and the $\pi$ electrons of cyclobutadiene in the complex is still $4$.
But this result contradicts with Huckel's rule, which states that the $\pi$ electrons should be $4n+2$. Where did I go wrong?


texts: Why is methane's molecular formula conventionally "CH₄", while water is "H₂O" (among others)?

texts:
While revisiting some of my old notes about the Miller-Urey experiment, I stumbled across the "equation"...

  Electricity + $\ce{CH4~/~ NH3~/~H2O~/~CO}$ = Amino Acids

This got me thinking.

Conventionally, why are molecules like $\ce{CH4}$ and $\ce{NH3}$'s molecular formula written differently (in H placement) than others like $\ce{H2O}$ and $\ce{HF}$? Is there a particular reason, or did it just happen to be?

NOTE: I realize the $\ce{H4C}$ or $\ce{H3N}$ make perfect sense, especially when drawing out molecules. It's just that these are rarely used in literature.


texts: How to name the compound with the formula Br3C-CHCl2?

texts:
Name the compound:

How should I name $\ce{Br3C-CHCl2}$? Is it 1,1,1-tribromo-2,2-dichloroethane or 2,2,2-tribromo-1,1-dichloroethane?


texts: Isomers of Octahedral Coordination Compound with Two Bidentate Ligands

texts:
Draw all possible isomers of $\ce{[CoNO2(en)2NH3]+}$

My answer:

I reckon that there are 4 isomers, as drawn above. Am I correct?


texts:
Black tea is an amazing product of the green tea leaves. A recent study has proven that;

  The anion profile for the tea solution indicated that oxalate and citrate were the major anions detected.

This resulted in the fact that a $\pu{1\!\% w\!/\!v}$ solution of normal (World Blend – Tetley USA Inc; you decide it for yourself!) tea has a pH of $\rm 4.9$. Non of these pieces of detailed info were an answer to my question.

My question is, definitely somehow oxalate and citrate managed to dissolve into water as we put tea leaves in it;

Where are they stored? (How does tea plant make them? I'm looking for the reactions that occur in the leaf)
How and why do they get released from tea leaf? Since you don't usually see any "big" differences between tea leaf and a soaked tea leaf? (I'm not looking for the how of solution)
What makes the color of water change? Why does the color vary with pH alteration? (There must be a reaction, what is it?)
Pt: These questions are additional questions to the title.


texts: What happens when tran-2-butene reacts with aqueous bromine in the presence of chloride?

texts:
$\ce{Br2-H2O}$, containing some $\ce{NaCl,AlCl3}$ ?

I initially though that there would be anti addition of Br and OH to give 3-Bromobutan-2-ol  but then I also got the intuition that NaCl might ionize in water and the $\ce{Cl-}$ might be involved here as well (obviously, with different stereochemical products)

But when I referred my book, it showed the following products only:

Why does this happen?


texts: How does chlorine form more than 1 bond?

texts:
How are perchlorate or chlorate or chlorite ions and their respective acids or compounds formed. $\ce{Cl}$ can't form more than one bond but still...

 $\rightarrow$'Perchlorate ion'

 $\rightarrow$'Chlorous acid containing Chlorite ion'

 $\rightarrow$'Chlorate ion'

Chlorine is making more than 1 bond... How is it possible?


texts: Has mercury(II) cyanate ever isolated as a free compound?

texts:
Recently, I have answered a question "Comparing explosive properties of mercury(II) cyanate and mercury(II) fulminate" where stability of cyanate vs fulminate was discussed. While I was answering that question, I found out that fulminate vs cyanate stability was previously discussed when chemical isomerism was discovered by Liebig and Wohler. They both reported independently that cyanic acid and fulminic acid that apparently had the same composition had very different characteristics and so they worked on the corresponding silver salts. These two compounds had the same chemical composition, yet are chemically different. Silver(I) fulminate is explosive, while silver(I) cyanate is a stable compound.
My thought process is that since silver(I) cyanate and silver(I) fulminate were extensively discussed to explain chemical isomerism, could that be applied for corresponding mercury compounds i.e mercury(II) cyanate and mercury(II) fulminate so that I could answer the previous question which was specifically asking for the stability/explosive properties of mercury(II) fulminate and mercury(II) cyanate. Mercury fulminate is well known in explosive industry and is used commercially. OTOH, mercury(II) cyanate is not very well known. I could hardly find any information of this compound, So, I assumed (incorrectly?) that mercury(II) cyanate is also unstable since it has not been isolated as a free compound and decompose explosively to a stable compound. Though mercury(II) cyanate is one of the decomposition intermediate of mercury(II) fulminate, I couldn't find any reaction of mercury(II) cyanate reacting or decomposing:
$$\ce{4 Hg(CNO)2 → 2 CO2 + N2 + HgO + 3 Hg(OCN)CN}$$
$$\ce{Hg(CNO)2 → 2 CO + N2 + Hg}$$
$$\ce{Hg(CNO)2 → :Hg(OCN)2}$$
$$\ce{2 Hg(CNO)2 → 2 CO2 + N2 + Hg + Hg(CN)2}$$
Also, I found in some e-books1,2 that $\ce{Hg(OCN)2}$ was apparently called mercury(II) fulminate which is clearly wrong and gave a notion that mercury(II) cyanate never existed/discovered. So, my questions are:

Why is mercury(II) cyanate poorly studied? Has it ever been isolated? Why is it "non-existent"?
Fulminates are even more unstable than cyanates and are considered sensitive compounds and thus difficult to isolate. So, in this case mercury(II) cyanate should be more stable and less sensitive than mercury(II) fulminate and yet the latter compound is studied extensively studied and the former one is yet to be isolated. Why?

Books:

Mercury study report to Congress, DIANE Publishing
Accounting for Resources, 2: The Life Cycle of Materials by Robert U. Ayres, Leslie Ayres, Leslie W. Ayres, Edward Elgar Publishing, 25-Nov-1999, Nature, 380 pages


texts: Is there any easy trick to know if a substance is a Brønsted–Lowry acid or base?

texts: I know that Brønsted–Lowry acids can donate a proton and a Brønsted–Lowry base can receive a proton. I have also memorized the strong acids and bases, which makes it easier to figure out. However, if I was given a substance that I didn't memorize, I would struggle to tell if it is an acid or base. Are there any quick methods to know if a substance is an acid or base? Or do I have to memorize as many as I can?


texts: How to calculate the percentage of calcium carbonate in sea shells in an experiment

texts: We have a investigation in my chemistry class in which we must calculate the amount of calcium carbonate in sea shells. We can have as many sea shells as we wish, lab equipment, and hydrochloric acid of varying concentration from $0.5~\mathrm{mol~dm^{-3}}$ to $2~\mathrm{mol~dm^{-3}}$. How is it to be done?


texts: Why don't plus one oxidation state metals form stable complexes with hydroxide ion?

texts:
For example, why doesn't AgOH exist as a stable compound?

I read that it rapidly decomposes to silver oxide and water.

$\ce{2AgOH -> Ag2O + H2O}$ $~~~~~~~~~pK_{decomposition}= 2.875$

http://actachemscand.org/pdf/acta_vol_14_p0717-0725.pdf

The above paper gives the pK value for the above equilibrium but doesn't bother to really delve into why silver hydroxide might be so unstable in water.

But why?

Is there repulsion between the silver cation and the proton?


texts: Miller indices. What determines the appropriate axis?

texts:
So, first of all, what's up with this "plane" I see two planes!

The basis of my question is that to determine miller indices the plane cannot lie on your origin, so you have to make a translation. If I move my origin to the right then I get the miller indices that are indicated in the figure. But if I move backwards then I don't get the miller indices in the figure.

So my question then is: what determines the appropriate translation?


texts: How is iron(III) chloride changed from solid to solution?

texts:
I'm conducting an experiment using iron(III) chloride in aqueous solution, but am also aware that it's usually a solid.

How is iron(III) chloride experimentally converted to a solution?

And can you please explain how the conversion happens and its mechanism.


texts: Interpretation of Figure - biofunctionalization

texts:
In this paper on page 1985 they say:

  Fluorescence analysis confirmed that enhanced protein binding at higher electron dose depends only to a small extent on the slight increase in the lateral dimensions of the nanodeposits but to a much larger degree on their height (Figure 4E)

  The amount of adsorbed IgG-Cy3 is largely independent of the actual area of the nominal 100 nm islands but scales with the height of the nanodeposits.

I don't understand this yet: why do I see that the fluorescence is proportional to area in this figure?


texts: Ligand Field Theory with non-identical ligands?

texts: Lots of undergraduate inorganic textbooks deal with complexes with $O_h$ or $T_d$ symmetry. So, if ligands are not same(like $\ce{[Ni(NH_3)_4(H_2O)_2]^{2+}}$), what methods are used to interpret their properties like electronic spectra?


texts: Will a dangerous amount of lead leach into soil from a galvanised corrugated steel raised bed?

texts:
I have searched, found similar questions but none answer my specific need.
I have built a raised garden bed to grow vegetables (ironically due to a high lead content in our garden soil - planning to put new, lead-free soil in the raised bed).
I used galvanised corrugated steel panels for the sides. I believe any zinc leaching would be beneficial, not a hazard.

However, now I learn that the galvanising process often involves lead. When something is "hot-dipped", apparently adding lead to the process helps the zinc run off. My understanding is limited. A crude 3M home swab test indicates lead, possibly a high content (it went very dark red).
https://en.wikipedia.org/wiki/Hot-dip_galvanization
https://galvanizeit.org/knowledgebase/article/why-is-lead-added-to-the-galvanizing-bath
My chemistry isn't very good, which is why I came to the experts. Here are my concerns:

How much lead would be likely to leach into the soil?
Would this lead be in a form that could be absorbed by lead-absorbing plants (e.g. lettuce)?
Would this lead be in a form that might endanger small children "helping" with the vegetables?
Would this lead be in a form that might be absorbed by the body when eating these vegetables, if not carefully washed?

Thanks in advance!


texts: How to separate two diastereomeric amines?

texts:
I am developing a method to synthesize amines using organometallic catalysts and my reaction yield these two diastereomeric amines ($\ce{R2N}$ is, in this case, a morpholine group).

With both being formed in approximate equal amounts, making it almost impossible to identify their structures by NMR without separating them. All the NMR spectra look like a mess since some signals get duplicated and some not. I have a hint that they are actually these two amines because they show the same molecular ion in the MS spectrum and the methodology used for synthesis offers little space for doubt, since it always forms the predicted structure.

I would like to know, if there is a practical way of separating those two compounds without using something super fancy like chiral column chromatography decorated with gold and antibodies kind of stuff. I have tried column chromatography but couldn't find a solvent system that could separate them. I also tried recrystallization (though I don't know exactly why I tried it), it also didn't work.


texts:
I have a 3L jug of SLA printer-related waste that's been sitting under my desk for a while now and I'd really like to finally figure out how to get rid of it. It contains:

Ethanol (primarily) and isopropanol, saturated (in the literal sense) with uncured resin (photo-polymers, photo-initiators, binders). Note there is likely very little water left (started with 90% ethanol and 99% iso, sieve-dried multiple times).
About 10% by volume undissolved waste, a slimy gray slurry of: uncured resin, a significant concentration of glass fibers, and some uninteresting filter waste (charcoal, sodium bentonite, probably some sieve dust, etc.)

Also it smells awful when unsealed, numerous recyclings through filters have left it disproportionately saturated with god knows what. It smells like ... pine and cancer.
How do I get rid of this? Is there some way I can process it myself to make it environmentally friendly? The uncured photopolymers are the worst offender, I believe. Plus the whole thing is very flammable.
Location: NYC (Kings County), NY USA
Also: I don't mind going through the effort of processing it myself if it keeps it out of the ocean or some landfill somewhere. Plus, I'll be continuing to generate this waste in the future (low volumes; probably about 1L per month at the highest rate) so I don't mind investing in a processing setup.


texts: What is the formula of bleaching powder?

texts:
What is the structure and preparation for bleaching powder?  Why there is a controversy in the formula of bleaching powder?

I have encountered many forms of the formula of bleaching powder, like

$\ce{Ca(OCl)2}$ - wikipedia (it also mentions that bleaching powder is actually a mixture having other calcium compounds in it)
$\ce{Ca(OCl)Cl}$ - my textbook
$\ce{CaCl2 + Ca(OH)2 + H2O -> CaCl2\cdot Ca(OH)2\cdot H2O}$ - here the product is "apparently" bleaching powder.

My question is posed in other sites like:-

http://www.chemicalforums.com/index.php?topic=48844.0 -
here it reads that the composition of bleaching powder has been disputed for decades.
http://chem-guide.blogspot.in/2010/04/preparation-properties-and-uses-of_6609.html - many forms  of the formula are given here in this site although none of it has been proved right! Also can you explain about this Odling concept of bleaching powder mentioned in this site?


texts: Why is antimony oxide used as a flame retardant?

texts: What is the mechanism of action of antimony oxide as a flame retardant? Is this to do with radical absorption?


texts: When can colourimetry be used to determine the rate of reaction?

texts: Can colourimetry be used if a coloured reactant react to give a coloured product? For example, in the reaction of reacting dichromate ions with oxalate ions in acidic environment, where dichormate ions (orange) react to give chromium three ions (green)?


texts: What causes triboluminescence and what process occurs to produce light?

texts: I have observed this effect by rubbing together two pieces of quartz in a dark room but am unable to explain this effect. Would it be something to do with the way quartz is bonded as a covalent network?


texts: Standard hydrogen electrode, why hydrogen?

texts: Why is the hydrogen electrode used as the reference to set electrode potentials? Could any other element be used instead?


texts: Comparison of rate of dehydration of primary, secondary & tertiary alcohols on cyclohexane

texts:
Rate of dehydration when given compounds are treated with conc. $\ce{H2SO4}$ is

According to me the answer should be $R > Q > S > P$ but my textbook solution gives the answer as R > Q > P > S (Sadly, there is no explanation).

Dehydration of secondary & tertiary alcohols in the presence of conc. $\ce{H2SO4}$ proceed through E1 mechanism whereas most primary alcohols proceed through E2 mechanism.

In the molecular R, the carbocation formed after the alcohol group leaves the molecule after protonation is a tertiary carbocation and not just that, it is resonance stabilized as well.

In the molecule Q, you get a secondary carbocation and this is resonance stabilized as well.

In molecule S, you get a secondary carbocation but there is no resonance stabilization.

In molecule P, the dehydration goes via E2 mechanism and there is a bulky cyclohexene group attached to the $\alpha$-carbon which should be contributing to steric hindrance.

If the question did not have molecule P, then its pretty much obvious that the answer is R > Q > S but with molecule P, I am not quite sure where to place it.

I thought that P will be least reactive since it proceeds via E2 mechanism and there is one bulky group attached to the carbon.

So how do I come up with a concrete answer to justify why molecule P should react faster than molecule S but slower than molecule Q.


texts: Why water vapors exerts pressure rather than diffusing in air before reaching the boiling point of water?

texts:
I am discussing only two types of vaporization in my question that are, evaporation and boiling. We know that evaporation is the phenomena which describes vaporization of liquid under a certain temperature. And boiling point is the temperature at which vapors of liquid exceeds their pressure by $760\ \mathrm{Torr}$ and starts escaping. The liquid doesn’t absorb more heat and utilize all of the heat to change its state and is said to boil.

There are more details about these two kinds but there is no need to discuss them right now so we should go back to the question that asks that why vapors exerts pressure rather than diffusing in atmosphere.


texts: Which ions determine ionic conductivity of a salt solution?

texts:
Let's take $\ce{ZnSO4}$ salt solution in water for example. So the ions inside my solution will be $\ce{H+}$, $\ce{OH-}$, $\ce{Zn^2+}$ and $\ce{SO4^2-}$.

My questions are:

Is the ionic conductivity measured for the solution gives an idea of mobility of zinc ions and sulfate, or is it a result of all four ions combined?
When we change the salt concentration of zinc sulfate, do we change the ionic conductivity of zinc and sulfate ions only, or all four ions?

Also, any undergrad university level source to understand this concept will be helpful.


texts: What's the reaction type of the Hydrogen shift?

texts:
Rearrangement of cycloheptatrienyl carbene yields heptafulvene via a hydrogen shift.

I see that the reaction is favorable because there is a conjugative effect with the $\pi$ system of the ring in the product.

Does this rearrangement happen by a radical TS or is the mechanism more of a sigmatropic rearrangement?

My arguments for

radical TS: The electron of the carbene (let's assume a singlet carbene here) lies close to the hydrogen, it could be a planar cyclic transition state.
[1,2]-Hydrogen shift: From my chemical intuition I think the $\ce{C-H}$ bond is more a polar bond and therefore I would hydrogen describe more as a proton (positive partial charge). I would say it's a [1,2] sigmatropic rearrangement, 2 electrons are involved, and therefore suprafacial and describing the carbene $\mathrm{sp^2}$ as HOMO and the hydrogen as LUMO.

What's the correct mechanism for this rearrangement?


texts: What does it mean for an equillibrium to move?

texts:
Le Chatelier's principle was described to me as:

  If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change.

I do not understand the phrase, "...the position of the equilibrium moves to counteract the change."

How can the equilibrium "move?" I know that the equilibrium constant cannot change so that cannot be it.


texts: How do I go about calculating the enthalpy of a solution with an unknown salt?

texts:
I have the $\Delta T$, I have the specific heat of the calorimeter, I have known weights/mass. I know the salt is lithium-based. What steps do I take to calculate the enthalpy of the solution so I can compare my answer to the specific molar enthalpies of possible lithium salts?
If the equation I use is $Q = m \times c \times \Delta T$, what mass do I use and do I use the specific heat of the calorimeter?
I just don't understand this. I've been hitting my head off the problem with research and trying to attack it from different directions and I'm just stuck.


texts: How to predict a good resonance structure?

texts:
I have to draw curved arrows to convert the above molecule to its resonance structure but I'm not entirely sure how. I believe the sulfur atom has one lone pair and the oxygen atom has 2 lone pairs. But how would I be able to predict the location of the curved arrows?

I took a look at their formal charge and both seem to be 0.


texts: Is free expansion of an ideal gas necessarily adiabatic?

texts:
I wanted to know if the term "free expansion" automatically implies an  adiabatic  vessel.Is it possible that there can be a transfer of heat in the free expansion of an ideal gas (as the term seems to imply to me that only external pressure is zero)?
Can we have something like Q=∆U


texts:
Value of standard electrode potential for the oxidation of Cl– ions is more positive than that of water, even then in the electrolysis of aqueous sodium chloride, why is Cl– oxidised at anode instead of water?

Standard electrode potentials describe the tendency of getting reduced.Positive value indicates that H2 can reduce that element or reduced form of the element is more stable than proton.
The answer to the question above is over potential
Please explain how it came into the story.My book explained it under "products of electrolysis",but the explanation is not lucid.
They explained it as :
Some electrochemical processes although feasible, are so slow that at  lower voltage these do not seem to take place and extra potential called over potential has to be applied which makes such process more difficult to occur.


texts: All alcohols are less acidic than water except methanol. Methyl group exhibits positive inductive effect. So water should be more acidic than water. But according to experimental evidence it is not so. Can someone explain the reason for this.


texts: I know that amylose and amylopectin are major constituents of starch. I also know the chemical structures of amylose and amylopectin. However, I want to determine how amylose and amylopectin bond together. I think that the OH from the amylose bonds with the HO of the amylopectin to form an oxygen bond and a water. Am I correct, or does the OH chain of amylose bond with the O chain of amylopectin?


texts: Heats of combustion of cycloalkane homologues

texts:
Heat of combustion increases as the number of carbons increases, but on comparing ethyl cyclopentane, ethyl cyclohexane, andethyl cycloheptane, shouldn't you consider ring stability too?

In that context, it should be 6-membered ring < 7-membered ring < 5-membered ring.

Why isn't this so?


texts: What is the oxidation state of copper and iron in chalcopyrite?

texts:
What is the oxidation state of Cu and Fe in chalcopyrite ($\ce{CuFeS2}$)?
Some websites tell that it is $\ce{Cu(I)Fe(III)S2}$, and others tell that it is $\ce{Cu(II)Fe(II)S2}$. Which is right?


texts: Base-promoted rearrangement of β-ketoester

texts:
Propose a reasonable mechanism for the following transformation:

I guess an enolate probably forms first, but then what does it attack to give something like the product in the question?


texts: Would there be a solid residue left behind from a reaction between NaK and H2O?

texts: I gather the reaction produces Sodium Oxide and Potassium Oxide as well as Hydrogen. Would there be traces of Sodium Oxide and Potassium Oxide left of a cloth that was positioned near the reaction? Thank a ton.


texts:
In group theory, in order to assign a point group, one must first identify the symmetry elements present in the molecule.

To give an example, water has:

a rotational axis, labelled C2 since it is a two fold axis, with a π/2 rotation giving back (what appears to be)the same thing
two mirror planes, labelled σv and σv' (with additional labels xy/xz to define what plane the mirror plane lies in)

Symmetry elements present in water

(Note that for the C2v point group, the axis are defined 'arbitrarily', different tables/books might swap x and y)

From this, it would look like water has three unique symmetry elements, however this is not the case, in fact, water has four due to the presence of an additional symmetry element, E, known as the identity operator (sometimes seen as I in certain textbooks).

This E operator corresponds to 'do nothing' (i.e. leave atoms where they are), which is easily seen in the character table for the C2v point group (to which water belongs) in which the characters under E are all '1':

$$\begin{array}{c|cccc|cc} \hline
C_\mathrm{2v} & \color{red}{E} & C_2 & \sigma_\mathrm{v}(xz) & \sigma_\mathrm{v}'(yz) & & \\ \hline
\mathrm{A_1} & \color{red}{1} & 1 & 1 & 1 & z & x^2, y^2, z^2 \\
\mathrm{A_2} & \color{red}{1} & 1 & -1 & -1 & R_z & xy \\
\mathrm{B_1} & \color{red}{1} & -1 & 1 & -1 & x, R_y & xz \\
\mathrm{B_2} & \color{red}{1} & -1 & -1 & 1 & y, R_x & yz \\ \hline
\end{array}$$

$\,$

C2v character table, from orthocresol's Group Theory Tables

  The identity, E, consists of doing nothing; the corresponding symmetry element is the entire object. Because every molecule is indistinguishable from itself if nothing is done to it, every object possesses at least the identity element. (Taken from Atkins' Physical Chemistry).

Since transforming a molecule by the identity operator just gives back itself, the use of 'E' in a qualitative sense appears redundant, however it appears in every character table, and as such much have a purpose.

Why do we need the identity operator, E, and what use does it have in chemical group-theory?


texts: How to calculate the rate constant at different temperature for the decomposition of dinitrogen pentoxide?

texts:
For the reaction
  $$ \ce{2N2O5(g) -> 4NO2 + O2(g)} $$
  the rate law is:
  $$ \frac{\mathrm{d}[\ce{O2}]}{\mathrm{d}t} = k[\ce{N2O5}] $$
  At $\pu{300 K}$, the half-life is $\pu{2.50E4 s}$ and the activation energy is $\pu{103.3 kJ/mol}$.
  What is the rate constant at $\pu{350 K}$?

I know there is something fishy about the rate law, but I can't make sense of it.

\begin{align}
\frac{ln2}{k} &= \pu{2.50E4}\\
k &= \pu{2.773E-5}\\
\frac{\pu{2.773E-5}}{k_2} &= \frac{A\cdot\exp\left\{\frac{-103300}{8.314\times300}\right\} }{ A\cdot\exp\left\{\frac{-103300}{8.314\times350}\right\}}\\
\end{align}

Finding $k_2$ from this gives me a weird value: $k_2 = 0.0103$.
The answer for this question is $\pu{7.47E-8 s^-1}$.

Where have I gone wrong?


texts: Why does substance that sublime not come to liquid state?

texts: A substance that sublimates doesn't come to a liquid state at room temperature. But when we melt the substance it melts! Why does it skip the liquid state at room temperature?


texts: If the equilibrium constant in a reaction is greater than 1 is it possible that there are more moles of reactants than products?

texts: I'm wondering if this is possible because could there not be a situation in which the reactants were pure solids/liquids and would therefore not contribute to the value of k but still contain more total moles that the product side?


texts:
Assuming ocahedral complex, The answer should be 4 as there can be 0,1,2,3 Cl- inside the coordination sphere. But, in many places the case with 3 Cl inside the coordination sphere is not present, answer provided is 3.

Loong's answer says otherwise. Only this answer and another answer in a linked question acknowledge the existence of the 3 Cl form. Every other place simply states that only 3 forms have been experimentally discovered.

Also, in coordinatiom isomerism too, in the case where both spheres become uncharged is ignored.

What is the reason?


texts:
I have an idea through utilizing soda lime or other basic substances to help solve climate change. I want to see if there are some possible errors or other negative implication that I am disregarding.

I came across soda lime during one of my biology textbooks and noticed that it has the ability to absorb $\ce{CO2}$. The first thing that popped into my head was utilising soda lime ($\ce{CaHNaO2}$) to help solve global warming.

My idea is having large or wide buildings that are made with soda lime on the edge that will "suck up" the carbon dioxide. This carbon dioxide can then be used for various different ways in which the community and the society can benefit from.

convert it to electricity or fuel (it has been said that there is a way of doing this as in Cornell University Research - YouTube video). Essentially, the electricity made would be redistributed to the city  to use.
export the gas to bread industries (the yeast produces carbon dioxide that may be used for brewing and for bakery)
if possible, change the carbon dioxide to oxygen and release oxygen.

I know I might not be aware of some factors and it may seem idealistic, but I want to hear from the community. Is what I am proposing realistic enough? Or are there some practical problems with this approach?


texts: What is the geometric formula of CaI2 and AlCl3

texts: Well, I think $\ce{CaI2}$ is the same as $\ce{BeH2}$ and $\ce{AlCl3}$ the same as $\ce{NH3}$, but I'm not sure since $\ce{I}$ and $\ce{Cl}$ have their own pair electrons and I don't know if this affects the structure...


texts:
Do E2 elimination reactions occur in alkenes? If not, what mechanism is used?

If they do, are they limited by any stereochemical rules as alkanes do (antiperiplanar)?

My question is pernitent to the alkyne reaction mechanism, where both the E and Z alkenes undergo elimination to form the alkyne.

My guess is E2 mechanism is possible for the Z alkene, while the E alkene undergoes E1


texts: I've been looking for a while and I still can't get a straight answer. I just need to know the lowest CAS Registry Number on record and the corresponding chemical.


texts: What is the mechanism of formation of Grignard's Reagent?

texts: What is the mechanism of formation of Grignard reagents? I couldn't find much in my book or on the Internet. This page says something which I am unable to understand. Why are the $2$ electrons in the $\ce{Mg}$ separated? Shouldn't they be together?


texts: Mechanism for addition of hydrogen halides in Alkynes

texts:
There is a question in my book where one is supposed to add 2 moles of HCl to But-2-yne.
I've attempted this and got 2,3- Chlorobutane instead of 2,2-chlorobutane which is given as the answer.
I'm unable to attach a photo of the same.
My doubt is, after one chlorine has been attached and the triple bond has been changed to double bond, why is the second Chlorine also attached to the same position as the first one.
One explanation, I think -
Since due to inductive effect of first chlorine, there should be delta plus charge near the chlorine attached atom, so H+ from second Hcl molecule goes to the adjacent atom. Therefore,  same C atom has both Chlorine.
But if I think other wise, as in stability of Carbocation and carbanion, adjacent C atoms 2,3 are getting Chlorine.
Please help me clear the doubt


texts: Most computer chips contain or are made of silicon. Why silicon? Why not copper or tellurium or some such?


texts: Electrophilic addition of HX to 2,3-dimethylbut-2-ene

texts:
Generally, for the addition of dry HX to an alkene, it follows Markovnikov's rule. The hydrogen atom adds to the carbon with the most hydrogen atoms.

However, in the case of an alkene which does not have any hydrogen atom attached to its carbon, such as 2,3-dimethyl2-butene, would the electrophilic addition still take place?


texts:
I am a high school student and I am very confused in salt hydrolysis
My confusion is that: when we talk of hydrolysis of salt of weak base and weak acid, we internally assume the degree of hydrolysis of both cation and anion of the salt is assumed to be same but I think it is a very wrong assumption, why don't we simply do the pH calculation like I have done in this example? what is the problem with this?,if my approach is also correct then why doesn't it matches with the standard answer? what is the mistake in it? I have found some similar questions but no one has given the exact answer to those that's why I am asking it here please, explain it in a simplified way because I am only at high school level.


texts:
This question is a continuation of the previous question of mine:press me if you wish

And my question is how can I dope a solid with impurities and if the process can be understood with basic knowledge of solid state physics.


texts:
I was presented with the following compound and asked to comment on the splitting of the proton $\ce{H_a}$ in $\ce{^1H}$ NMR.

The question presented today was:

  What is the chemical shift (below) and splitting pattern for $\ce{H_a}$ up to and
  including $\ce{^4J}$?

I relabelled the molecule as shown:

but I was left stuck here. I know that $\ce{H_a}$ will be split by $\ce{H_d}$ and $\ce{H_e}$ to give a doublet of doublets (dd) but I was wondering, since the molecule is asymmetric. Now

are the protons $\ce{H_c}$ and $\ce{H_d}$ chemically equivalent but magnetically inequivalent

to yield the final splitting pattern as dddd?


texts: Tabulated absorption spectra of greenhouse gases?

texts:
Are there any free sources of tabulated absorption spectra of greenhouse gases from UV/Vis to far infrared (say 70 micrometers)?

This link shows the net absorption over the whole atmosphere (at least as far as I understand it), but I would be interested in the absorption by an infinitesimally small volume/distance. It would suffice to have the spectra for just one temperature, like $\pu{273K}$ or so.

On the NIST site I have found some information, for example IR spectrum of $\ce{H2O}$ vapor, but apart from the limited spectral window the spectrum is pretty useless for making a radiation simulation because concentration info was missing (as said in the disclaimer).

Is there still hope of getting accurate spectra suitable for understanding molecule specific greenhouse effects?


texts:
Identify functional groups of the following organic molecule:

A. ketone, alkene, carboxylic acid, ester
B. alkyne, ester, carboxylic acid, aldehyde
C. carboxylic acid, alkene, ketone, ester
D. ester, aldehyde, carboxylic acid, alkene

I am not sure what the answer it. I know it can't be B because there is no alkyne triple bond. However, shouldn't an alkene only exist in a straight chain? I know there is a COOH carboxylic acid, R-O-R' ether and a CHO aldehyde, and a double bond O for a ketone.
I was wondering if someone could tell the right answer.


texts: CO poisoning - What I've been taught is a hoax?

texts:
In elementary school, I happened to ask my teacher:

  What is $\ce{CO}$ they talk about these days?

I was then taught that Carbon monoxide "competes" with the oxygen in our blood (we were  taught that oxygen gets to our cells via blood at that time) and replaces it and thus, doesn't let enough O get to cells and this will be fatal in extreme cases.

I didn't do any research about it after that because I later made the implication that $\ce{CO}$ is able to replace O and react with Hb instead; but

I recently became doubtful about my previous lessons and decided to do a research to see what really was going on:

  Carbon monoxide mainly causes adverse effects in humans by combining with hemoglobin to form carboxyhemoglobin (HbCO) in the blood. This prevents hemoglobin from releasing oxygen in tissues, effectively reducing the oxygen-carrying capacity of the blood, leading to hypoxia. Additionally, myoglobin and mitochondrial cytochrome oxidase are thought to be adversely affected. Carboxyhemoglobin can revert to hemoglobin, but the recovery takes time because the HbCO complex is fairly stable. Wikipedia, CO poisoning

Wikipedia states that the problems are:

$\ce{CO}$ is able to combine with Hb to form HbCO.
This compound is fairly stable, so we'll have a hard time removing $\ce{CO}$ from hemoglobin.

Other sources, such as How stuff works, Answers.com and CDC.gov have given either only more explicit explanations of wikipedia, or the explanations weren't "chemical-biology" enough.

I haven't seen a single reference in which the first assumption was declined, or agreed with. Is what I'd learnt non-scientific?


texts: What is the difference between carboxylate ions and groups?

texts: I would like to know the difference between carboxylate ions carboxyl groups? An example is is $\ce{COOH}$ and $\ce{COO}$.


texts: Mechanism of substitution reaction with no change in stereochemistry

texts:
When (2S,3R)-3-iodobutan-2-ol undergoes a substitution reaction with sodium azide the only organic product from the reaction is (2S,3R)-3-azidobutan-2-ol. Give a mechanism for the reaction.

My Attempt

Now I know this is not a normal $\mathrm{S_N1}$ or $\mathrm{S_N2}$ reaction since the stereochemistry remains the same and only one of the enantiomers are formed. I am guessing that at first there is some intramolecular reaction where the iodine atom attacks the other carbon bonded with the hydroxyl group. Then the azide substitutes the iodine atom.


texts: Change in internal energy of a gas upon expansion against a constant external pressure

texts:
I have a question about the following problem which I got wrong:

During expansion of its volume from $\mathrm{1.00\,L}$ to $\mathrm{10.00\,L}$ against a constant external pressure of $\mathrm{2.00\,atm}$, a gas absorbs $\mathrm{200\,J}$ of energy as heat. Calculate the change in internal energy of the gas.

First, I used the equation: change in $E = q + w$. I calculated work ($-P \Delta V$) and found it to be
$$-18 = -2 \cdot (10 - 1)$$. Then, I added $-18 + q$, the heat absorbed ($\mathrm{200\,J}$). This gave me a result of $\mathrm{-182\,J}$, which is wrong by a large factor. My textbook gives the answer of $\mathrm{-1623\,J}$, but I am not sure where I am going wrong...

Do you know where I made a mistake? Thank you!


texts: Preparation of Copper (II) Sulfate Pentahydrate Solution

texts: how would you make a solution of Copper (II) Sulfate Pentahydrate to achieve 150, 200, 250 and 300 mgL−1 concentration of copper? I do not have the anhydrous version of the solute. Also, when I dissolve it in water, does it become acidic? If so, how would I maintain it at pH 7 without messing up the concentration? I am going to use the solution for adsorption studies if anyone is asking. thanks for the replies!


texts: How can a titration help me figure out the effect of rosmarinic acid on amylase activity?

texts:
So with my limited knowledge of rosmarinic acid, I am aware that it is an non-competitive inhibitor and can inhibit the enzyme, amylase. When starch is added to a solution of already mixed rosmarinic acid and amylase, it doesn’t break down due to the inhibition.

A titration was used to investigate the effect of rosmarinic acid on amylase. The solution containing the rosmarinic acid was put into a burette and was the titrant for this experiment whilst the potassium permanganate was the titrate.

I have a few questions about this experiment. Why was a titration used and how could it identify if the rosmarinic did have an effect on the amylase? Also, why was the solution containing rosmarinic acid the titrant instead of the titrate? What is the potassium permanganate’s role in this investigation?


texts: How can a protein folding transition state have zero lifetime?

texts:
I'm doing a module on my Biochemistry course looking at protein folding, and in a discussion of [folding] transition states I was a little confused at the thought of a zero-lifetime transition state - especially as for folding "the TS is probably an ensemble of states (a population) with a lifetime of 0".

In searching for anything with mention of protein folding TS with lifetime of 0 I found this old discussion ported to Google Groups, in which this is described as an 'inherent contradiction' to TS theory.

  ..."capital K, double dagger" is defined as a *thermodynamic equilibrium
  constant*.  So, for example, a Transition State Theory applied to a
  bimolecular reaction involves a term corresponding to the
  *thermodynamic equilibrium constant* for the transition state [AB]**.   At the same time, the transition state itself is presumed to have
  *zero lifetime*.

  In other words, the Transition State Theory is wonderfully
  self-contradictory in its very essence (it contains an *equilibrium*
  constant for something that has zero lifetime). (via)

I'm just wondering if anyone can enlighten me / agree / disagree with this, and maybe suggest some of the original literature I might go to for an understanding of the meaning to this.

One of my chemistry textbooks has a small section on Hammond's postulate but without explanation to why transient is defined as zero lifetime:

Further, it's possible I've brought myself to the wrong equations but if I understand correctly the mass balance equation (described from the source above as the reason TS is only a 'quasi-steady state') says here the dm/dt does not tend to zero, i.e. zero lifetime is overextrapolation of the theory :

  one can assume steady state for a species as long as its production
  rate and its lifetime t have both remained approximately constant for
  a time period much longer than t. When the production rate and t both
  vary but on time scales longer than t, the steady-state assumption is
  still applicable even though the concentration of the species keeps
  changing; such a situation is called quasi steady state or dynamic
  equilibrium. The way to understand steady state in this situation is
  to appreciate that the loss rate of the species is limited by its
  production rate, so that production and loss rates remain roughly
  equal at all times. Even though dm/dt never tends to zero, it is
  always small relative to the production and loss rates. (via)

Please let me know in comments if I can make this question more clear, thanks.

Update: This is a question about protein folding transition states - please can you not give me answers or comments directing me to resources covering the basics of transition state theory.


texts:
Sometimes the concept "manifold" is used in quantum chemistry, for instance,
in Calculation of size‐intensive transition moments from the coupled cluster singles and doubles linear response function:

  where $\tau_{2s}$ and $\tau_{2t}$ denote the singlet-singlet and triplet-triplet spin coupled double excitation manifolds where spin couplings initially are carried out on the occupied-occupied and unoccupied-unoccupied orbital indices.

However, in general, manifold refers to a geometric object that is locally Euclidian. This is not essential to the coupled cluster method.

My question is, what is the motivation to introduce manifolds in the coupled cluster method?


texts: Titration of weak acid and strong base at low concentrations

texts:
Titration continues until one of the reactants (the one in conical flask) turns out to be a limiting agent as far as I know. From the titration of a weak acid and a strong base, I could learn that the end point is above $\mathrm{pH \ 7}$ since weak acids do not ionize completely. Till this point I could understand everything. But I had a confusion at the condition of ions at end point. In this titration, we are basically dealing with $\ce{H+}$ ions dissociated from water (which is very low) and acid. Usually acids remain a bit more concentrated and release more ions than water does. That is at end point we often ignore the auto ionization of water.
But what if we are dealing with such acid whose concentration leads to total amount of dissociated $\ce{H+}$ ions comparable to $\pu{1 \times 10^{-7} M}$. Will titration be an appropriate way to determine the concentration of acid in this case? Or we need to use some other ways to measure the concentration?
Please let me know if there is any point I'm missing out regarding this topic. And this is my first question in this forum so I'm looking for cooperation. Any help will be appreciated.


texts: Molarity Numerical on Water Gas Shift Reaction

texts:
For the water gas shift reaction below, $K_c = 3.491$ at a certain temperature. What are the equilibrium concentrations of all the components of the reaction if $\pu{0.3815 mol}$ of $\ce{CO}$ and $\ce{H2O}$ are initially mixed in a $\pu{250 mL}$ flask?
$$\ce{CO(g) + H2O(g) <=> CO2(g) + H2(g)}$$

I was able to calculate the molarity of $\ce{CO}$ and $\ce{H2O}$ and set up an ICE table, but my answer seemed inaccurate. My work so far:
$$3.491 = \frac{[\ce{CO2}][\ce{H2}]}{[\ce{CO}][\ce{H2O}]}$$
$$3.491 = \frac{x^2}{(1.526-x)^2}$$
Because $x$ should be much smaller than $1.5$, it can be ignored when squaring $1.526$. Therefore, $3.491 = x^2/2.32$
$$3.491\cdot 2.32 = x^2$$
The square root of that value is $2.85$, which is impossible because there weren't $\pu{2.85 mol}$ of $\ce{CO}$ or $\ce{H2O}$ to begin with.


texts: What is the principle of diffuse reflectance spectroscopy behind band gap measurement?

texts:
As the title suggest can you explain how DRS can be used for finding band gap of a material. Below is an DRS output result:

From the figure we can see that at about 465 nm the reflectance drops steeply with respect to wavelength and attain a plateau at around 420 nm. Using above data we can assume that the band gap is around 2.76 eV (450 nm).

Can you explain this figure in  physical sense (i.e. with respect to the material)?
Why do we take the energy of a ~450 nm photon as the band gap? What is the rationale behind it?


texts:
In one of my organic chemistry experiments, I synthesized tetracyclone (Tetraphenylcyclopentadienone), and we were supposed to dissolve it in DCM to do our TLC.

DCM is polar and looking at the structure of tetracyclone I think it is non polar, isn't there a saying that "like dissolves like"? Then how could tetracyclone dissolve in DCM?

Below is the structure of DCM and tetracyclone:

Edit: After searching online, I found that due to the lack in ability to form hydrogen bonds, we treat DCM as a non polar solvent, even though it is weakly polar.

Website: https://www.quora.com/Is-CH2Cl2-both-polar-and-non-polar-Why


texts:
As a non chemist I tried to read to understand if active carbon acts in solutions as an acid or a base but I understood that it can act as both, depends on the material which used to make the solution.

For example, mixing a sodium bicarbonate with active carbon in a solution will make that solution with higher PH (hence a stronger base, per my understanding).

Is it correct to say that active carbon is an enhancer of either acid or base?


texts: How to determine the potential of a cadmium zinc cell under standard conditions?

texts:
I write the half-equations:
\begin{align}
\ce{Zn &<=> Zn^2+ + 2e^-}& E^\circ &= +0.763~\pu{V}\\
\ce{Cd^2+  + 2e- &<=> Cd}& E^\circ &= +0.403~\pu{V}
\end{align}

In order to find the $E_\mathrm{cell}$ is it right to say:
$$E_\mathrm{cell} = 0.763~\pu{V} + 0.403~\pu{V} = 1.166~\pu{V}?$$

Or should I say $0.403~\pu{V} - 0.763~\pu{V}$?


texts: can you explain the structure of gemtuzumab ozogamicin? where are the linker boundaries?

texts: could someone help me to decipher the structure of this molecule? I am trying to understand the structure of gemtuzumab ozogamicin: The anti-CD33 antibody is acylated with the bifunctional AcBut linker, which allows for hydrazone formation with the calicheamicin derivative. This derivative, N-acetyl-gcalicheamicin dimethylhydrazide (DMH), has a disulfide stabilized by both the two methyl groups and the calicheamicin bicyclic core, and an acetylated amino sugar. References: Joel C. Barrish, Percy H. Carter, Peter T. W. Cheng, Robert Zahler Accou... I would like to know the boundaries of AcBut linker. I got confused because in this picture it is depicted like that:  I thought that DMH was the part after the benzyl ring in the linker. Thank you in advance!


texts: What does the osmotic pressure do in an electrolytic solution?

texts:
I have learnt that in an electrochemical cell, the osmotic pressure in the solution hinders the flow of ions from the electrode to the solution, rather some ions may accumulate on the electrode because of this osmotic pressure. As far as I know, osmotic pressure is a measurement of the tendency of the solvent molecule to flow from one solution to another.

My question is, how does this pressure cause the ions in the solution to gather at the electode?


texts: What is the reason for strong acids/bases dissociating in water?

texts:
I have read that the actual definition of a strong acid is one which will fully dissociate in water, so please do not turn the problem on its head when answering. It is also my understanding that every acid reaction is in fact reversible (just as with any other reaction) and yet the thing that is different about strong acid forward reactions is that they are shifted so far forward (the equilibrium constant is very high) to the extent that hardly any of the reactants remain after reaction. The acid reactions follow the laws of chemical reaction kinetics and the reason for this is that the Gibbs free energy decrease of the acid reaction is fairly high and so according to a Maxwell-Boltzmann Curve of energy distributions, only a very small fraction of the molecules will have enough energy to actually revert back to their undissociated form.

My real question is what is it about the electronic (or otherwise) structure of these compounds, for example $\ce{HCl}$, as opposed to weak acids, e.g. $\ce{CH3COOH}$, that makes them more easily dissociated in water. It might also be helpful to learn the same about strong and weak bases. I think it might have something to do with the electronegativity of the ions involved.

If you can help answer the above, please could you also explain the weak/strong conjugate rule (that if a weak/strong acid/base reacts it will produce a strong/weak conjugate base/acid respectively).


texts: Why does ammonia have a pKa of 32.5 at −33 °C?

texts: According to Wikipedia, ammonia has a $\mathrm{p}K_\mathrm{a}$ of $32.5$ at $\pu{-33 °C}.$  Why does it say that? Is it a typo? Isn't anything above $12$ is a very strong base? And both bases and acids are slightly stronger at higher temperatures, not lower, correct?


texts: The main component of tooth enamel is calcium hydroxyapatite. I know fluoride ions can replace hydroxide ions in the enamel matrix, slowing the rate of enamel demineralization. Why does hydrofluoric acid dissolved in water have no adverse health effects on other areas of the mouth? I suspect that its because the fluoride is in low enough concentrations to help your teeth and not harm the gums.


texts: How can be explained why the specific heat of ice is twice as low as liquid water?

texts:
To raise the temperature one degree of ice costs about 2000J but for liquid water it is 4000J.
The reason for that is that the freedoms of vibrations rotation and translations of ice are lower and the molecules of liquid can move more freely.

But I don't understand that. I would say that when molecules can move more freely it would take less energy to raise it one degree, because heat is actionally movement. But why isn't that through?


texts: Aromatic nomenclature, when to use numbers or prefixes?

texts: When you're naming aromatic nomenclature compounds, when do use numbers, such as 2,4-diiodonitrobenzene and when do you use prefixes such as p-xylenene? Thanks! I hope that makes some sense


texts: How to determine the mass of ammonium nitrate needed and enthalpy of solution?

texts:
I am trying to figure out how to determine the mass of ammonium nitrate needed to reduce the temperature of solution from $\pu{23 ^\circ C}$ (measured room temperature at start) to $\pu{3 ^\circ C}$, once it dissolves in water.

I have the formula:

$$Q=ms\Delta T$$

I looked up the enthalpy of solution for ammonium nitrate and found it to be $\pu{25.41 kJ/mol}$.

I also have data that if I add $\pu{15 g}$ of $\ce{NH4NO3}$ the temperature will decrease by $\pu{25 ^\circ C}$, if I add $\pu{10 g}$ the temperature will decrease by $\pu{20 ^\circ C}$, and if I add $\pu{5 g}$ the temperature will decrease $\pu{13 ^\circ C}$.

Clearly then, to get my solution to be $\pu{3 ^\circ C}$, I would need to add a mass somewhere in between $10$ and $\pu{15 g}$.  In the lab I could just add random amounts between until the solution settled on $\pu{3 ^\circ C}$. Shouldn't there be a mathematical way to solve this rather than by random guessing?

I tried to use $Q=ms\Delta T$ by substituting the enthalpy of solution (in J) for $Q$, the specific heat of water for $s$, and $\pu{20 ^\circ C}$ for $\Delta T$ (since I am going from $23$ to $\pu{3 ^\circ C}$). However, solving $$\pu{25410 J} = m (\pu{4.186 J// ^\circ C})(\pu{20 ^\circ C})$$ gives me $\pu{303.66 g}$ which is clearly nowhere near the $\pu{10 - 1 g}$ that is sufficient to change the temperature.

How can I accurately determine the mass using a formula?


texts: Why does liquid water form when we exhale on a mirror?

texts:
In the descriptions below, I always assume external pressure to be constant at 1 atm, the condition where daily observations are made.

1) When I exhale on a mirror, liquid water forms on the mirror. That's condensation. Obviously, the temperature of mirror must be < 100 °C, so water vapor condensing on mirror makes sense.  However, in that case why do we have water vapor in our breath when our body temperature is also < 100 °C in the first place?

2) One reason for (1) may be like 'water vapors in air is in equilibrium with liquid water', so some water vapors can exist although T < 100 °C. If this is correct, based on this reasoning, then why doesn't ice exist at T > 0 °C? [p = 1 atm only]

3) If liquid water can evaporate into gas at T < 100 °C, then why doesn't ice turn into liquid at T < 0 °C? (I never use the term 'melt' here, just like evaporate≠boil) (both have hydrogen bonds, intermolecular forces should be the same?)

4) When I exhale on a wall, no water droplets form. Why do water droplets form on mirror but not on wall (just an example)? The mirror must have the same temperature as that of the wall, both of them must have achieved thermal equilibrium with their surroundings a long time ago.


texts: How to read electron energy levels abbreviations?

texts:
The electron energy transfer diagrams I've been coming across all have energy levels labeled as e.g. $^{2}F_{5/2}$ or $^{4}S_{3/2}$. I've tried to Google "quantum energy level abbreviations" but haven't come across anything too useful, just explanations of electron configurations. Can anyone explain or point to a website or textbook that goes through what these numbers/letters/fractions mean for someone who's taken general chemistry but not quantum mechanics?

Thanks!


texts: What are the effects of heating paraffin wax above it's melting point

texts: I'm working with a paraffin embedding station that we recently learned was overshooting it's set point (60C) and heating paraffin to 100C. The problem has been corrected, but I'm curious what the mechanical/physical effects of paraffin being heated to almost twice the melting point. This is for a microtome setup (slicing at 5 microns) so micro features can and would be effected.


texts: Can benzaldehyde undergo chlorination (aka halogenation)?

texts:
I've read articles online and they rarely mention about chlorination of benzaldehyde but more on bromination.
Also, I would like to know the catalyst used for this is FeCl3 or AlCl3?
Thanks for your help!:)


texts: Shifting of axial and equatorial protons

texts: I know this NMR represents cyclohexanol and I have figured out what each peak represents. If the 3 peaks at 1.9, 1.7,1.5 all represent equatorial protons as they are shifted downfield compared to the axial. How does the peak at 1.3 represent 5 axial protons. Shouldn't they have split signals just like the equatorial protons, due to the electronegativity of the oxygen an its deshielding effect. Or is there a reason why axial protons aren't affected by the electronegativity of the Oxygen.


texts: What is the outcome of the following reaction?

texts:
The first step is clear to me, making an immine.
However how does the immine react again?
Perhaps it can be reacting with the carbonyl or alkene (to carbonyl over conjugation) I can't get to the target formula.


texts: Any idea why tap water goes stale overnight?

texts: We have great tap water here in Hungary. My only problem that it goes stale overnight sometimes in some glasses or sometimes even the 2L water boiler has this problem too. But microbes cannot resist 100°C or 20% vinegar, so I thought it might be rather a chemical compound what causes it. It is really hard to get rid of it. When I use boiling water or vinegar it does not remove it. When I use soap and water several times, it removes it most of the times, but only for a few days. The only working solution was not using the affected glass for a month. It is hard to descibe the taste, but it is something like how new Chinese clothes or paint thinner smell so it is sort of strong plastic taste. The longer I use a glass without washing it every day, the bigger the risk it develops this feature (2 days are enough for certain glasses, while others never develop it), so maybe microbes are producing it after all, but the compound is long lasting even if they die off. Any idea what causes it and more importantly how to get rid of it permanently without having to wash my glasses, boiler, water jug each day?


texts: Why does whipped cream use nitrous oxide instead of nitrogen gas?

texts: It seems that nitrous oxide $(\ce{N2O})$ is frequently used to create whipped cream. But why can't just regular nitrogen gas $(\ce{N2})$ be used instead?


texts:
Suppose in a piston in which there is a gas, the gas exerts pressure P on surroundings, whereas the surrounding exerts a pressure $P[ext]$ on the gas.

In order for the gas to expand, P must be greater than P[ext]. So far I understand. Suppose initially that $P>P[ext]$ and the gas expands until $ P=P[ext]$ This is what I don't understand is that when you calculate the work done by the gas, you use the external pressure and not the gas pressure. This makes no sense to me. After all, if you calculate the work done on something, you should use the force or pressure applied on that object, or not the other way around, correct? So why do we use external pressure instead of internal pressure when calculating the work done by the gas?


texts: What is the heat of reaction of weak acid reacting with weak base compared to strong acid reacting with strong base?

texts: My book has this line only that "weak acid and weak base reaction will produce lesser heat than constant enthalpy" of strong acid and strong base neutralization which is $\pu{-57.3 kJ/mol}$.


texts: Has a carbon analogue of poly(dimethylsiloxane) been synthesized?

texts:
Consider poly(dimethylsiloxane) (PDMS), a member of the family of silicone polymers:

Now, imagine its carbon analogue:

I've not been able to find any evidence that this carbon analogue has been experimentally prepared. Searching for "poly(dimethylalkoxane)" got me nowhere.  I eventually searched for "dimethyl polyoxymethylene," which turned up the unsubstituted variant of the above, polyoxymethylene (POM):

as well as methyl-capped POM oligomers, polyoxymethylene dimethyl ethers:

But, no "poly(dimethyloxymethylene)" was forthcoming.

Has the carbon analogue of poly(dimethylsiloxane) been synthesized? If so, what name has it been given?


texts: Is an epoxide opening more favorable than a chloride leaving in the same molecule?

texts:
In general, we've learned that alkoxide groups are awful leaving groups, unless we're talking about epoxide rings whose ring strain allow the alkoxide to act as a leaving group in a ring-opening reaction. However, if a structure contained both an epoxide and a relatively good leaving group like Chloride, what would predominate if a strong base/nucleophile was introduced: Epoxide opening or the substitution reaction? An example is provided below of what I'm referring to:

If I perform, the epoxide ring opening, I get something unusual:

I left the stereochemistry ambigious because I honestly did not know how to assign it since a new stereocenter is formed.

If I perform the Sn2 substitution, the reaction is completed quickly:

Notice that both of my proposed mechanism reform the epoxide ring, but do generate entirely different structures.


texts: Why is the silver salt ammoniated to form the Tollen's reagent?

texts: When doing a distinguishing test between aldehydes and ketones using Tollen's reagent, is it necessary to convert $\ce{Ag+}$ ions into $\ce{Ag(NH3)2+}$ in order to oxidize the aldehyde?


texts: Textbook chemistry vs Real life chemistry and impurities

texts:
Long ago when I took chemistry courses in high school and lower, chemistry seemed so simple and elegant. All equations and exercises involved pure elements, pure compounds, with a very clean simplified diagrams.

Now that I look at real world, the world is full of impurities. Even water we drink is not pure $\ce{H2O}$, but rather full of "other stuff", and no two samples of water are "absolutely identical".

This makes me wonder. To what extent can you overlook these impurities when doing science, in predicting outcomes of experiments.

For example, you can make naive formulas for how much salt can dissolve in water until it stops dissolving salt. However, in real world,

Pure water does not exist as something easily available, and if it does, from what I read, it doesn't stay pure for very long.
Table salt, while mostly sodium chloride, often contains iodine, and "other stuff" that I am not sure about.

So surely these impurities impact the behavior of your experiments, and depending on the experiment, you can get reactions you never expected or wanted, or behavior can be drastically different.

My question is, how do scientists control experiments when dealing with unpure compounds? How do they know that their reactions to produce "table salt" don't create unwanted chemicals that will blow up in small quantities, or create some new kind of poison that they will only be noticed in a few days? Perhaps create some kind of acid that burns through the glass of their beaker or cause some other hazardous effects. Are they naive and ready to face the unexpected or are there absolute certainties in which they can control it (can you really control everything?)?


texts: Generalized reaction rate and derivation

texts:
Most textbooks give the reaction rate

$$r = k C_\ce{A}^a C_\ce{B}^b  \tag{1}$$

for the elementary process $\ce{a A + b B -> P}$. However, expression (1) is not valid in the general case: e.g. it is lacking fluctuations, small-size corrections, memory effects, relativistic corrections,...

I have seen some derivations of the rate expression (1) using kinetic theory, Langevin approach, or chemical master equation, but the derivations introduced further approximations: e.g. the kinetic theory approach considered only binary collisions in diluted gases under local thermodynamic equilibrium.

Consider the process $\ce{A -> P}$, according to (1) the rate expression would be

$$r = k C_\ce{A}  \tag{2}$$

However this expression not only predicts an incorrect stationary state, but it does not represent the real concentration in the system, because $C_\ce{A}$ is only an averaged concentration and not the instantaneous concentration of species $\ce{A}$ in the system. In a first approach the above rate is replaced by

$$r = k \tilde{C}_\ce{A} + \tilde{f} \tag{3}$$

where $\tilde{C}_\ce{A}$ represents the real concentration in the system and $\tilde{f}$ is a stochastic chemical 'force'. Now (3) represents the rate of the real concentration and it gives the correct stationary limit. (3) satisfies a fluctuations-dissipation theorem that relates $\langle\tilde{f}(t)\tilde{f}(t')\rangle$ to the rate constant $k$. This relation is used in experimental methods that measure chemical fluctuations to obtain the rate constant.

Equation (3) continues being an approximation, a generalization could be the introduction of memory effects, which could give something as

$$r = \int_0^t \kappa(s) \tilde{C}_\ce{A}(t-s) ds + \tilde{F} \tag{4}$$

where the kernel $\kappa$ and the generalized stochastic 'force' $\tilde{F}$ have complex expressions, but (4) continues being an approximation. Consider now the process $\ce{2A -> P}$, according to (1) the rate expression would be

$$r = k C_\ce{A}^2  \tag{5}$$

but this is not correct in general. Introduce the volume factors into $k$ to obtain

$$r = K N_\ce{A}^2  \tag{6}$$

and you can check this predicts a rate $r=K$ when $N_\ce{A}=1$, which is obviously impossible because at least two molecules are needed for the step. The rate (6) is invalid for mesoscopic systems (e.g. reactions involving small amounts of matter in living cells) and it is also incorrect for large systems in the long time limit, when $N_\ce{A} \rightarrow 0$. A corrected rate is given by

$$r = K N_\ce{A} (N_\ce{A} -1)  \tag{7}$$

which cannot be derived from (1). However, (7) can be derived in combinatorial kinetics, which postulates the next rate expression for an elementary process $\ce{a A + b B -> P}$

$$r = K \frac{N_\ce{A}!}{(N_\ce{A} - a)!} \frac{N_\ce{B}!}{(N_\ce{B} - b)!}  \tag{8}$$

But again (8) is an approximation.

Each rate expression I find in the literature is valid only for some specific cases, but fails for others.

What is the general expression for the reaction rate for an elementary process and how can the expression be derived from first-principles?


texts:
My professor of bioengineering said that all foods produce urea. Do foods exist which does not produce urea?

Thank you very much.


texts: Galvanic Electrochemical Cell Without half cells

texts:
Is it possible to create a galvanic cell without a half cell?

In the book I was reading, Illustrated Guide to Home Chemistry Experiments, the following lab (Laboratory 16.4) was suggested:

add 2 M HCl and add copper metal to one end of the beaker, with magnesium at the other end. Then, add patch cables to connect the metal plate to an LED to have physical evidence of success.

However, I don't understand how useful work could be generated without half cells.

To my understanding, we add HCl to react with the magnesium and copper, to produce ions ($\ce{Cu+}$ and $\ce{Mg^2+}$). Then, they can spontaneously produce work due to their eV differences.

What I am missing is how the work can be useful, as opposed to just generating heat in the solution.

I would believe that, rather than traveling though the patch cables, electrons can travel directly through the solution and produce heat.

Thanks for reading and I really appreciate any help!


texts:
P forms $\ce{P4}$ due to its inability to form double/triple bonds. So it makes a sort of tetrahedral structure.
S however makes $\ce{S8}$ cycles w/ $sp^2$ hybridization. Why go all that way to connect the chain? Can't $\ce{S3}$ do the trick? It will still have $sp^2$. What makes $\ce{S8}$ more stable?


texts: Why on loosing aromatic chracter still product produced is 90% in the following reaction?

texts:
In Birch reduction reactant loses it aromatic chracter  but still the product found is to be 90%.
By loosing aromaticity product must be less stable so less amount of product must be formed.
 Why still on loosing product found is to be 90%?


texts:
(I know this is a bit off topic, but I don't know where else to ask. If you know a better StackExchange site, please tell me)
I'm working on a project, and I want to basically create a "flaming sail". For this, I'm planning to drench a cloth in methanol and then lighting it, and for this, I need a fabric that both retains a lot of moisture and is flame proof, as this should be reusable.


texts: 3-step process to make propyl ethanoate from propene

texts:
I was asked to make propyl ethanoate from propene in three steps. I have access to the reactions below.

Nucleophilic substitution (Both SN1 and SN2)
Electrophilic addition
Hydrogenation
Dehydration
Hydration
Condensation
Free radical substitution
Oxidation of alcohols

I'm assuming that you can add whatever reactants you want, since propyl ethanoate has five carbons and you can't just chop a carbon off of a propene with the above reactions. I know that the final step has to be condensation, since that's how you make esters. So essentially, I need a two-step process to make a primary alcohol that becomes the propyl in propyl ethanoate.

If you use hydrogenation on propene first, you get propane. Once you have that, it takes two steps to make a primary alcohol: one in free radical substitution (to get 1-bromopropane) and one in nucleophilic substitution (to get propan-1-ol).

If you use hydration first, you get a secondary alcohol in one step. However, you can't make propyl ethanoate with propan-2-ol.

If you use electrophilic addition first, you get a secondary haloalkane (2-bromopropane). That can also only get you a secondary alcohol.

Does anyone know how to do this? I'm convinced that it's impossible to do.


texts: Oxidation of alkenes and alkynes by Chromic Oxide?

texts: As far as I know, $\ce{CrO3}$ doesn't effect the $\mathrm{\pi}$ bonds in an inert medium like pyridine. Would $\ce{CrO3}$ in acidic medium reduce alkynes to have the same products as acidified, warm $\ce{KMnO4}$ would have? Or does it produce diketones similar to reductive ozonolysis?


texts: Why is the pure tungsten (W) melting point higher than that of its oxides (either WO3 or WO2)?

texts: Why is the pure tungsten ($\ce{W}$) melting point way higher than that of its oxides $\ce{WO3}$ or $\ce{WO2}$? And why does pure $\ce{Al}$ react differently? I.e. the oxides have a higher melting point than pure $\ce{Al}$.


texts: Thermodynamic and kinetic products - carbocation stability

texts:
The professor wants to know which is the thermodynamic product and which is the kinetic product.

He says there are only two products - the two on the right that result from the resonance-stabilized complex. I can see a third product - the product on the far left with the question mark over an arrow.

The argument for the far right product being the kinetic product is that it is a tertiary carbocation and therefore the energy barrier to formation is probably lower than the energy barrier to formation of the secondary carbocation.

Alright, sure. However, could one also argue that the far left product is the kinetic product? It is after all the result of a tertiary carbocation. And it is the result of a "pure" tertiary carbocation - not a tertiary carbocation "diluted" by resonance; the far right product results from a resonance-stabilized complex that has both secondary and tertiary carbocation character. This was something I thought of at first. But then I realized I was probably taking resonance contributors too literally and that the resonance-stabilized complex would probably be more favored intermediate because the positive charge is "delocalized".

So what's your take?


texts: Suggestions for research into different fluids in heat pipes

texts:
I'm doing some research on heat pipes (check here for wiki). One of the things I'm planning to do is try some different fluids in the pipes. Water (commonly used) has a freezing point that's too high, so I'm looking into fluids that don't freeze up in winter and disrupt the equilibrium in the pipe.

I've randomly picked ethanol so far, but I'm looking for suggestions from someone more knowledgeable then me.

I'm mainly interested in vertical heat pipes that don't need a wick like here on wikipedia, but rely on gravity to get the drops of condensed fluid back to the warmer area.

Potential things that could matter:

Viscosity of the fluid
Bubble forming at boiling point (bubbles can form an isolating barrier perhaps?), is there a fluid that boils in vacuum with very small bubbles?
Surface tension

All suggestions are very welcome, please explain why you think a certain fluid is a good choice.

Thanks in advance,

Johan Rensink


texts: What is meant by fractional oxidation state?

texts: What is the real concept behind oxidation state?


texts: Green and red crystals of [Ni(Ph2EtP)2Br2]

texts:
From the reaction of $\ce{NiBr2}$ and $\ce{Ph2EtP}$, it is possible to isolate green and red crystals of $\ce{[Ni(Ph2EtP)2Br2]}$?
A) coordination number and geometries of the complexes?
B) possible isomeric structures for the green and red crystals.

I know that d orbitals effect the color but I don't know how to apply it to isomers.


texts: How to stop a lye + oil + water reaction in aluminium container?

texts:
I was making soap using a guide for the first time. I accidentally used an aluminium container. It has lye and olive oil in it and was kept on the stove; now it is bubbling and not ceasing (I've turned off the gas).

What should I do to stop it?


texts: How much water evaporates during a given time?

texts:
I read some questions such this  for example and I asked me another question. Instead of only calculate how much time does it takes to have a cup of tea at room temperature, I'm asking how much time does is take to evaporate a part of the water in a cup of tea.

Just to be clear

For this question I am considering that the cup is full of water at 100°C and the cup too. The cup is consider to have no effect on heat transfert and has a high of $12 \mathrm{\text{ cm}}$. During all the experience the temperature and the pressure in the room are constant and respectively are $T_0 =20^\circ \mathrm{C}$ and $P_0 = 101325 \mathrm{\text{ Pa}}$.

From the beginning of the experiment to the time where the temperature of water and the cup will be the same than the room it is not difficult to imagine that some water will evaportate and escape the cup and goes in air. But don't forget that their is an equilibrum between water in the liquid water and the water in the air. We will considering during all the time of the experiment the hygrometry of the air is zero. So then by the diffusion phenomena very very slowly the water in the cup will escape.

At the end we assume the pressure of water in the air is the saturation pressure of water in the air and there is only $5 \text{ cm}$ of water inside the cup.

My Question

We know how to calculate the time for water to cool from $T_0$ and room temperature. How should I know then during this time how much water goes out of the cup in gas phase ?

"this time" refers to the time for the water to goes from $\text{100}^\circ\text{C}$ to room temperature. The time during the water at room temperature will diffuse in the air is given in the next part with details for you.

Some details for you

I'm asking this question because I know how to calculate the time to evaporate water using law of diffusion but this time depends on the high of liquids there is in the cup ...

My calculus give :

$$t=\frac{\left(z_f^2-z_i^2\right) \rho RT_0}{2M_{H_2O} P_0 \mathcal{D}_{w/a} \ln\left(\frac{1-y_i}{1-y_f}\right)}$$

Where :

$z$ is the difference lengh between the top of the cup and the top of the water, $\rho$ is the density of water at $T_0$, $M_{H_2O}$ is the molar weight of water, $\mathcal{D_{w/a}}$ is the diffusion coefficient of water in the air and $y$ is the molar fraction of water in the air.

If we consider for example that until room temperature only $0.5 \text{ cm}$ of water evaporates then $t=5426025 \text{ s}$ I just need know the real value of how much centimeters really escaped.

Sorry for the lengh of the question and thank you in advance for your answer !


texts: Can electrostatic interaction affect nucleophilic attack by thiolate anion

texts:
Suppose a protein side chain has a $\ce{-SH}$ group which is partially deprotonated to thiolate anion $\ce{-S -}$. This thiolate can perform a nucleophilic attack on a certain substrate.

Will the propensity of nucleophilic attack be reduced if the thiolate anion is in electrostatic interaction with a $\ce{NH3+}$ group of a basic amino acid? Or is the likelihood of nucleophilic attack independent of electrostatic effects?

P.S.- The $\ce{-S-}$ will probably be in eletrostatic interaction with H+ in the solution also. Maybe electrostatic interaction with $\ce{NH3+}$ will be more stable?

Core question: If a negative nucleophile is in electrostatic interaction, will it affect its nucleophilicity?


texts:
Is this an error? Why is the nitro group reduced as the benzene ring is oxidized? I don't see any possible reducing agents here..

Also, what is the mechanism of aromatic fluorination by xenon difluoride? This appears analogous to electrophilic aromatic substitution in which benzene acts as a nucleophile and attacks an electrophile because of the expected meta-substitution pattern given the presence of the nitro group.

Is fluorine really electrophilic here? How so?


texts: Is it possible to put wax or PE or any kind of insoluble coating on soluble material (e.g. edible film)?

texts: I'm working on a project to make a cup that can holds hot/cold water inside but can be dissolved from the outside. I'm just wondering if that would be possible scientifically??


texts:
Below is the structure of Ace-Ala-Nme. I have labelled just four of the carbon atoms (1-4 in blue). I need to identify (i) the hybridization state, and (ii) the number of electron withdrawing groups for each.

I believe the amine (-NH) groups are electron donating while the carbonyls (-CO) are electron withdrawing. I therefore suspect that all four labelled carbon atoms are sp3 with 0 withdrawing groups. But this is assuming that the donating/withdrawing tendency of the amine and carbonyls cancel each other out. Can anyone confirm this to be the case?


texts: Why do alkanes have higher boiling point than their ether counterparts?

texts:
Based on my understanding of inter-molecular forces, I expect dipole-dipole interactions to be significantly stronger than van der Waal's interactions. Hence, I expect ethers (which obviously have dipole-dipole interactions) to have higher boiling points (as boiling point $\propto $ inter-molecular forces) than alkanes (assuming approximately the same molecular mass). But, the experimental data suggests otherwise.

$$
\begin{array}{|c|c|c|c|}
\hline
\textbf{Compound}&\textbf{Boiling point / °C} &\textbf{Compound}&\textbf{Boiling point / °C} \\ \hline
\textit{n}\text{-pentane}  & 36.1   & \text{ethoxyethane}  & 34.6    \\ \hline
\textit{n}\text{-heptane}  & 98.42  & \text{1-propoxypropane} & 90 \\ \hline
\textit{n}\text{-nonane}   & 151    & \text{1-butoxybutane}  & 141   \\ \hline
\textit{n}\text{-undecane} & 196    & \text{1-pentoxypentane}& 184   \\ \hline
\end{array}
$$

As evident, experimental data suggests that alkanes are on par with ethers when it comes to inter-molecular forces, infact the former are slightly higher.

I tried to reason this discrepancy as follows. Ethers have weak dipole, so their dipole-dipole interactions will also be weak (though stronger than their van der Waal's interactions). Alkanes on, the other hand, have van der Waal's forces only but I suspect that size is playing a dominant role here. Ethers have a v-shaped bent structure, and therefore, have reduced surface area as compared to alkanes. Therefore, I believe that alkanes lead over ether in this case and this compensates the weak dipole of ethers. Though this is only a hypothesis from my part.

But there is another problem:

\begin{array}{|c|c|c|c|}
\hline
\textbf{Compound}&\textbf{Boiling point / °C} &\textbf{Compound}&\textbf{Boiling point / °C} \\ \hline
\text{propane} & -42 & \text{methoxymethane} & -24 \\ \hline
\end{array}

Now at this point I am out of ideas. From $\ce{Et-O-Et}$ to $\ce{Pe-O-Pe}$ we had ethers leading over alkanes which felt odd but when we compare di methyl ether and propane, everything just seems fine with ether having the dominating lead (as expected initially). What is real cause? Am I missing some important concept here? Or is there any other factor that I am not considering?


texts: Can reactions produce microwave or radio wave radiation?

texts: I know that many reactions produce visible light,  heat and sound,  but is there a reaction (preferably one example for an inorganic and organic one)  that could produce electromagnetic waves in the microwave and radio band?


texts: When amino acids react with each other, how do you know which one reacts using it's carboxylic group and which one with it's amine group?

texts: For example the dipeptide val-ser, between the amino acids valine and serine, does valine's amino group react or does it's carboxylic group with serine's respective group?


texts:
Is a hydrogen atom bonded to the first and the last unit of polyethene?
If yes, where does the hydrogen come from?


texts: while using Henry's law does it matter if the solvent is volatile or not?

texts:
I am studying about binary solutions (with liquid solvents) and came across Henry's law. This is how it's stated in my textbook:

  Henry's law states that at a constant temperature the solubility of a
  gas in a liquid is directly proportional to the partial pressure of
  the gas present above the surface of the solution.

The way it's been stated does not say if the liquid solution is volatile or not.

So, while using this law, does it matter if the liquid solvent is volatile or non volatile?


texts: How to compute the electron configuration of an atom?

texts:
How to compute the electron configuration of an (electrically neutral) atom ?

So when given the atom number how does one compute the electron configuration ?

I know the sum of electrons must equal the atomic number.

I also know the first shells fill up as $2n^2$.

I do not know how to compute quantum numbers when given the atom number.


texts: There are some non-classical carbocations, such as the 2-norbornyl cation, in which the positive charge is heavily delocalised. Have non-classical carbanions also been discovered? I have not seen any non-classical carbanions in books. If there are any non-classical carbanions, please provide some examples.


texts: Identifying Alkyl Ligands as Pi Donors or Pi Acceptors in Transition Metal Complexes

texts:
Just wondering if there was a systematic way to identify an alkyl ligand as a $\pi$ acceptor or $\pi$ donor in a transition metal complex?

Although various sources indicate that weak field ligands are typically $\pi$ donors and strong field ligands are $\pi$ acceptors, I'm having trouble with the more uncommon ligands not listed in the spectrochemical species, namely $\ce{CH2}$ groups directly double-bonded to metals, or $\ce{CH2-tBu}$ groups double bonded to ligands.


texts: The molecular orbitals of lithium hydride

texts:
So my understanding of molecular orbitals is as follows: the molecular orbitals of $\ce{LiH}$ can be thought of as being formed from the interaction/overlap of two atomic orbitals, one from lithium and one from hydrogen in this case. I also understand that the atomic orbitals have to be quite close in energy for any significant interaction to take place.

The occupied atomic orbitals of lithium are 1s and 2s, with energies of around -66 eV and $\pu{-5.3eV}$ respectively. The occupied atomic orbital of hydrogen is 1s, with an energy of -13.6 eV. I believe that it's safe to assume that the 1s orbital of lithium is far too low in energy to interact with the 1s orbital from hydrogen, meaning that only the interactions are between the 2s orbital of lithium and the 1s orbital of hydrogen, producing a bonding MO and an anti-bonding MO.

Wikipedia states that "Bonding MOs are lower in energy than the atomic orbitals that combine to produce them." In other words, the 2$\sigma$ bonding MO should have an energy less than -13.6 eV, which is the energy of the 1s hydrogen orbital. However, computer  calculations of the MOs of LiH show that this bonding MO has an energy of -8eV. which would seem to contradict the statement from Wikipedia.

So assuming there is no fault in my reasoning so far, we can safely say that this Wikipedia statement is only generally true, and false in this particular case. So why is this?

I was trying to rationalise this as follows: generally, the reason why bonding MOs are lower in energy than the atomic orbitals used to create them is because bonding MOs concentrate electron density between the two nuclei, resulting in the electrons being attracted by both nuclei (as opposed to just one), leading to the MO being lower in energy than the original AOs. However, in LiH, due to the energy of the 1s AO on hydrogen being significantly lower than that of the 2s AO on lithium, the 1s AO will be the major contributor to the bonding MO, meaning that the electron density in the bonding MO will be significantly closer to hydrogen's nucleus than lithium's nucleus.

Now, originally, there is one electron each in the 1s hydrogen AO and 2s lithium AO, and when they come together, two things change: Firstly, there is electron-electron repulsion between these two electrons. Secondly, the electrons are now bound by two nuclei rather than 1. However, due to the high polarity of the bond, this second change is minimal, such that the first change (introduction of repulsion) actually outweighs the second change, meaning that the resulting bonding MO is actually higher in energy than the hydrogen 1s AO.

Is my rationalization of this accurate/correct? If not, please suggest alternative explanations/ improvements to my thought process because I'm frankly not fully convinced by myself.


texts: DIY hand sanitiser solution forms spongy substance

texts:
I am trying to make my own hand sanitiser since it’s sold out everywhere. The formula I use is 1 part aloe vera gel in 2 parts 100% isopropyl alcohol. The problem is when mixing the two, the solution always forms a small white spongy sticky substance while the rest stays liquid, not gel-like:

I tried two brands of aloe vera gel and got the same result:

Palmer Aloe vera gel: Aloe Vera Gel (Aloe Barbadensis), Polyglycerylmethacrylate, Propylene Glycol, Witch Hazel, Algae Extract (Algae), PPG-2-Isodeceth-12, Carbomer, Tocopheryl Acetate, Triethanolamine, Methyl Gluceth-20, DMDM Hydantoin, Tetrasodium EDTA, Quaternium-15, Fragrance (Parfum), Hexyl Cinnamal, Linalool, Geraniol, Limonene, Yellow 5 (CI 19140), Blue 1 (CI 42090).
Thursday Plantation Aloe Vera Gel: Aloe Vera inner leaf juice equiv. to fresh 974mg/g, Hydroxybenzoates, Diazolidinylurea, Potassium Sorbate and Sodium Benzoate

I am starting to think I got the wrong type of alcohol but the label clearly says pure 100% isopropyl alcohol.

What am I doing wrong?


texts: Can the compounds NOF3 and POF3 both exist?Why?

texts:
Today I came across a question (in one of my books) like

  Can the compounds $\ce{NOF3}$ and $\ce{POF3}$ both exist? Why?

After some googling I found that both of them do indeed exist. I can understand that $\ce{P}$ can extend its octet due to empty d orbitals. But $\ce{N}$ can't do so. So how can it possibly exist?


texts: What happens when unsaturated primary alcohol is reacted with acidic potassium dichromate?

texts: It is clear that the hydroxy group in the substrate gets oxidised to carboxylic acid. But what happens to the double/triple bond in the unsaturated primary alcohol when it reacts with acidic potassium dichromate?


texts:
I'm trying to grow oyster mushrooms that like high temperatures. They look great in an indoor terrarium, and can eventually yield several tasty meals :)

However oyster mushrooms are hard to grow indoors, because they need low $\ce{CO2}$ levels (<1000 ppm according to Paul Stamets), AND high humidity (>95%).

Warm climate oysters tend to grow fast, and can generate quite a lot of $\ce{CO2}$ fast.

If I vent the air in tent about 10 times a day, humidity will suffer (and I can't do that all the time).

If I close the tent, mushrooms will be stunted and club-like, and yields will be next to nothing.

I'm thinking about putting a tray with $\ce{NaOH}$ crytals on it, probably with a fan to slightly move the humid air around a bit.

An other method would be to use an aquarium pump to bubble air through NaOH solution.

My questions are:

Does this look like something feasible? Can some $\ce{NaOH}$ remove enough $\ce{CO2}$ from the air to keep it under 1000ppm?
Which of the above methods seem to be the better one given the aquarium pump can bubble about 100-200 litres of air in every hour and the tent is about 500 L ?


texts: What is the most simple way to cut through a steel with very thin aluminum coating to obtain cross section without damaging the coating?

texts: I needed to take cross section characterization of an aluminum coating. I tried to use a hand saw to cut through it, but it destroys the coating, and usually is separated with the substrate as I exerted force in using the tool. What can I do to get a cross section part without damaging the thin coating/film?


texts: Similarity between Ecell and equilibrium constant Kc

texts:
$$\ce{Cu^{2+} + Zn<=>Zn^{2+} + Cu}$$

$K_c=1.9*10^{37}$

$E_{cell}=1.1V$

I know that they both suggest that the forward reaction is going to completion but can someone please tell me a bit more about what both these values are suggesting and how these two values concord with each other.

Also, many books quote such reactions in only one direction and gives a value for $E_{cell}$. However, isn't $E_{cell}$ just another way of illustrating the condition of an equilibrium (i.e. in which direction the reaction would occur if left alone)... so how can a one way reation be shown


texts: Would the electrolysis of alcohol, specifically spirits, result in a potable end product? I'm looking for some novel cocktail ingredients.


texts: What happened when the cherry juice turned blue?

texts:
When I was eating cherries today, some of its juice spilled on my shirt. Attempting to clean it, I poured a solution (baking soda, vinegar, toothpaste, and salt) onto the fabric. Though it did not remove the stain, the colour turned from a wine red to a subtle blue.

So the Question is: Why did it happen?

(This is not that technical so I'm not sure how to classify it)


texts: Is the spin of the transferred 4s electron always opposite to the spin of 3d electron in chromium?

texts:
I am studying atomic structure and found out that Chromium has an exception in electronic configuration. One electron from 4s jumps to 3d to achieve stability.
let's say the spin of transferred electron is +1/2. Then the other 4s electron should have -1/2. Then, are all the 3d electrons of +1/2 spin or some may have -1/2 spin too?


texts: The number of geometrical isomers of complex of type [Ma₃b₂c]

texts:
Find out the number of geometrical isomers of the complex $\ce{[Ma_3b_2c]}.$

I applied simple combinations to get the number of isomers as
$$\frac{6!}{3!\,2!} = 60.$$
However, my book states that only three geometrical isomers are possible. I could not see why simple combination is not giving the correct answer.


texts: How to know if computational calculations are correct

texts:
I've recently been modelling some transition states of a reaction I've been doing (read: struggling to do).

Whilst I have a lot of technical support in doing this (both step by step help and also academics who research in the field of computational chemistry), one thing that bugs me is the difficulty in knowing whether the calculation is meaningful.

In synthetic chemistry, I can do an experiment, then take an NMR/crystal structure, and be confident that i've got what I was intending to do. Whilst different bases may promote different reactions, its always possible to work out whats happened.

In computational chemistry, I do a calculation and get an answer, however depending on the methods used the answer might change.

This can be minimal: isomer A is favoured over isomer B, but the extent changes depending on the basis set/experiment. Or can be significant: isomer A and B change their order.

I was wondering if there is any way of telling whether a calculation is relevant. Obviously experiment can do this, but the reason I'm doing the calculation to begin with is to try and rationalise the difficulties in reaction .

Is there a concrete way to quantify the 'meaningfulness' of a computational result, or is it always a case of just fitting the computational data to experiment and then working backwards.


texts: Beryllium chloride - Highly hydrolysable?

texts:
Beryllium chloride's geometric structure is linear, with a bond angle of 180 degrees. Drawing the Lewis dot structure for this covalent compound, one can see that the compound is electron deficient and requires two lone pairs to achieve stability. As a result it is a strong Lewis acid. Since water has two lone pairs and is a strong Lewis base, mixing beryllium chloride with water results in stability for beryllium chloride and the evolution of energy.
My question is, why don't two lone pairs from either chlorine atom or even just a single chlorine atom make a coordinate bond with beryllium, as can be seen in the case of carbon monoxide where one of oxygen's lone pairs is donated to carbon to achieve nearest noble gas configuration of neon. If such a compound does not naturally exist, why does it not? Is it a theoretical defect or is there some explanation?


texts: Why is the conjugate of a strong oxidizing agent a weak reducing agent?

texts:
I am a grade 12 student. While I was reviewing some electrochemistry, I had the following question. Take this reduction half-reaction:

$$\ce{F2 (g) + 2e- <=> 2F- (aq) + $\pu{2.87V}$}$$

I know that $\ce{F2 (g)}$ is a strong oxidizing agent, but why does this make $\ce{F- {(aq)}}$ a weak reducing agent? I thought that since the electrical potential of the reduction half-reaction:

$$\ce{2 F- (aq) <=> F2 (g) + 2 e-}$$

was $\pu{-2.87 V}$. Therefore, should $\ce{F- (aq)}$ not be a strong reducing agent?


texts: Why is lanthanum a lanthanide and actinium an actinide?

texts:
I do know that the lanthanides start with the element lanthanum, but why? Lanthanum doesn't even have an $f$ orbital, so why isn't it considered a transition metal?

It's the same way with actinium, which doesn't even have any electrons in its $5f$ orbital, why isn't it also a transition metal?


texts: How do I calculate weight/number average relative molecular mass for polymers?

texts:
I have to estimate the weight/number average relative molecular mass of following diagram:

I know the equations:

I just can't interpret the diagram. Do I use the chain length as mass of the individual polymer?

I would then get $\pu{M_w = 52.305}$
and  $\pu{M_n = 68.227}$

Is this alright? I really appreciate any help.


texts: Looking for a dye which emits around 680 nm

texts: For a specific experiment, I'm looking for a dye which would emit around 680 nm. Preferably one I could buy easily commercially. Are there any databases which might give the emission spectra of specific dyes? Or any other methods to find dyes at around $\ce{680 nm}$.


texts: Calculating Vmax (or Kcat) given specific activity of an enzyme over length of time incubated with an activator

texts:
Is it possible to figure out the $V_\mathrm{max}$ (or $k_\mathrm{cat}$) and/or $K_\mathrm m$ from a plot of enzyme activity expressed as specific activity over time (i.e. $\mathrm{U/mg}$ on the $Y$ and time on the $x$ axis). I've figured out how to express specific activity as turnover but I'm not sure this helps with calculating $V_\mathrm{max}$ or $k_\mathrm{cat}$.

The reaction:
p38 phosphorylates MSK1 with Michaelis–Menten kinetics

Experimental conditions:
$1\ \mathrm{U/mL}$ of p38 was added at time $t=0\ \mathrm s$ to a solution containing MSK1. They don't say how much MSK1 but express its activity as $\mathrm{U/mg}$ (which is analogous to $\mathrm{(\mu mol/min)/mL}$, otherwise known as specific activity)

The Data:

Time         MSK1 activity
(s)          ((µmol/min)/mg)
__________________________________________________
   0               0
 300             175
 600             350
1200             450
1800             475
2400             500

Calculated turnover:

Time         MSK1 turnover
(s)          (1/(nmol s))
__________________________________________________
 18000          300
 36000          600
 72000         1200
108000         1800
144000         2400
     0            0

In actual fact, I though $k_{\rm cat}$ was the turnover and that this was a constant, specific for each enzyme. This data however suggests that as the reaction progresses more MSK1 is produced the turnover number increases, which makes sense and therefore calls into question the two definitions of $k_{\rm cat}$.