texts: How much energy water "captures" at it evaporates in room temperature?

texts:
As explained in Why does water evaporate spontaneously at room temperature despite ΔG > 0? water evaporates in room temperature because partial pressure of water is less than "standard" conditions of air in normal atmosphere.

If I need to evaporate or boil 100 g of water to artificially increase humidity of air over time, does it make any difference in total energy comsuption if I slowly evaporate the water or if I boil it rapidly? Common sense seems to indicate that rapidly boiling the water takes much more energy but is it really so? I would not be surprised if slowly evaporating the water would take exactly the same amount of energy (which would cause slight temperature drop in room temperature) but I don't know how to compute or demonstrate this. Does it make a difference if the room is considered big but closed or the room is open to atmosphere? If it makes difference for this discussion let's say that humidity of air in room is 25% RH and the room temperature is 25°C.


texts: Is the number of tetrahedral voids always equal to double the number of octahedral voids in any crystal?

texts:
I came accross the question whether the number of tetrahedal voids is always equal to twice the number of octahedral voids (in the case where both the voids are present). The key was given as the statement was true. Could anyone justify this?
I know that it is true for ccp and hcp but can this be generalized for all types of crystals?


texts: What gas was produced in this orbiting space-balloon from 33 pounds of benzoic acid and anthraquinone? Why these two chemicals?

texts:
As pointed out in this answer, on page 4 of NASA Technical Note TND-1366 The Orbital Behavior of the Echo I Satellite and its Rocket Casing During the First 500 Days (June, 1962) says:

PHYSICAL CHARACTERISTICS

Echo I has an effective cross-sectional area of 7,854 square feet. The launch weight of 157 pounds decreased to 124 pounds with the loss of 33 pounds of benzoic acid and anthraquinone which were used to maintain inflation for the first few  weeks in orbit. Thus, the initial ratio of the weight to mean drag area for Echo I was 0.020 pound per square foot and reduced to 0.016 pound per square foot after several weeks in orbit.

Echo-1 was about 100 feet in diameter, so that change in weight of 0.004 pound per square foot of drag area corresponds to the 35 pounds mentioned.
Questions:

What kind gas would have been produced by this mixture, and what fraction of the initial mass would have been converted to gas? Could it have been all of it as suggested? (the idea is that after the gas leaked out the balloon would have become rigid enough to retain its shape while in orbit.
Why both benzoic acid and anthraquinone? Did they react? Did they sublimate only? Is there any chemistry-related reason why both substances were used?

below x2: cropped and full size from Echo, NASA's First Communications Satellite


texts: I have a dynamic assay whose absorbance changes with time. I recorded it’s spectrum initially after preparing it. Then I added my analyte and mixed the contents. Then I waited for 2 min and recorded the second absorbance soectrum. I generated a normalized standard calibration curve by dividing the absorbance maximas (captured 2 min post analyte addition) at different analyte concentrations (1M, 2M, 3M...)  by an average value of control (initial absorbance maxima before analyte addition). Is this approach correct? My ordinate is normalized absorbance and abscissa is concentration of analyte.


texts: Is there something which will block liquids but is dissolved by blood?

texts:
Is there a material which can be applied to a surface that will block liquids but is dissolved by blood?

The idea is to use the liquid to close a circuit, but only if blood is present.

I'm wondering if there is something I can coat on the circuit to act as a barrier preventing other liquids from reaching the circuit, but that would react to the chemical components of blood by dissolving, allowing the blood to reach and close the circuit.

One application might be in a bandage, to detect if a wound has reopened. The number of liquids in that context is pretty limited. A limited number of false positive edge cases is also acceptable


texts: Why is the bond angle H-P-H smaller than H-N-H?

texts:
$\ce{N}$ & $\ce{P}$ are in the same group. Both $\ce{NH3}$ and $\ce{PH3}$ have one lone pair and according to VSEPR theory, both the central atoms are predicted to be $\ce{sp^3}$ hybridized.

But in spite of that, the bond angle in the former is $107^\circ$ while that in the latter is $92^\circ$. What is the cause of such a difference?


texts:
I recently encountered a question while solving previous year question papers for JEE.

This is a JEE 2005 question.

The question demands to complete this statement:

  Equimolar solutions in the same solvent have _______

There are four options and the correct answers are

  same boiling point

and

  same freezing point

I don't think this is correct as the change in boiling and freezing point depends on molality and not molarity. Hence, according to the options, the one saying different boiling and freezing points seems to be correct to me, however, such exams very rarely have mistakes which are not corrected later.

Please clarify.


texts: Is the 'sweat' on the side of bottles distilled water?

texts: Are the water droplets that form on the side of water bottles (or other drink containers) distilled water? Assume that the sides of the container are completely clean.


texts: Volatile (aroma/scent-defining) compounds from Himalayan Balsam (Impatiens glandulifera)?

texts:
Has anyone identified the compound(s) that make up the distinctive and intense scent of Himalayan Balsam (Impatiens glandulifera)?

I’ve found a number of compounds associated with Impatiens sp., but it does not look like any of them would be carriers of the scent:

2-Methoxy-1,4-naphthoquinone or "lawsone methyl ether" [an anti-inflammatory, fungicidal agent]
2-Hydroxy-1,4-naphthoquinone (Lawsone) [a dye that is also the principal component of Henna]
Methylene-3,3'-bilawsone (Diphthiocol; 3-[bis(2-hydroxy-1,4-naphthoquinonyl)]methane)
α-Parinaric acid [a polyunsaturated fatty acid]

Neither the naphthoquinones nor the fatty acid are described as having any particular scent, and they are apparently all non-volatile solids, which would rule them out.

I was unable to find any more information online, but maybe someone who is more involved with this kind of research has some pointers. Thank you!


texts: Diluting methanol in water: is it exothermic?

texts: Can someone explain in simple terms why does temperature increase when mixing water with methanol? I do not have a strong background in chemistry, but I usually have to mix both liquids (sometimes also water + ethanol) (as part of my work in a biology lab) and have always wandered about the reason behind the evident increase of temperature upon mixing. I guess that the break/formation of H-bonds is involved but I haven't found a clear ("easy-to-understand") explanation in online searches.


texts: How can HCl be liquid if it has a boiling point at -85°C?

texts:
Shouldn't it at least be boiling? When water reaches its boiling point it makes bubbles, but that doesn't happen with HCl, why?

Did I misunderstand some basic chemistry?


texts: Can diastereomers form a racemic mixture?

texts: In my book, it says racemic mixture is the mixture of + and - optical isomers and it is optically inactive. This means enantiomers (optical isomers which are mirror images to each other) can form racemic mixture. But can diastereomers (optical isomers which are not mirror image to each other) form a racemic mixture?


texts:
Why does acid reacts with skin??

I can understand the acid would react with blood as it is alkaline in nature. But when i googled pH of skin, its around 4-5, "it is estimated that the 'natural' skin surface pH is on average 4.7, i.e. below 5"(Reference) The thing that i could guess is that only H+ are the ions that would react with our skin since only H+ are common in every acid. But since our skin is also acidic how will an acid react with another acidic material


texts:
Will acids really donate a proton? In an atom, the proton is inside the nucleus and I don't think a proton will go all the way out of atom dodging all electrons and enter into the nucleus of the base.

It seem impossible but the Brønsted–Lowry theory says acids donate protons.

I am confused—could someone explain what is actually meant by acids donating protons?


texts:
In cathode ray tube experiment in order to check the direction of flow of electrons a hole was made in a note and behind it phosphorescent material zinc sulfide it was coated.

Why does zinc sulfide glow when hit by electrons?
What causes this glow?


texts: What non-hazardous substance can be used to locally turn sky red?

texts:
I am a horror author and I have a scene coming up in my new book where I need a red-colored gas (or a gas that would somehow be turned or viewed red when viewed from the ground) to be spilled into the atmosphere. Preferably by a tanker truck.
I need this gas to kind of hang over this small community and of course, not kill anyone. Just an eerie red sky. I looked at sulfur hexafluoride, but I think that is colorless and maybe toxic? Looking for something that would make sense here.


texts:
Why does in the hydrolysis of acetylsalicylic acid with NaOH the solution has to be simmered gently?

What could happen if I would strongly boil it.
Would the OH- react into the carboxyl groups to form a diol?


texts: Why Add Salt to Vinegar to Clean Pennies?

texts:
One common cure for dirty pennies is to put them in vinegar and salt. The vinegar should react with the copper oxide on the penny in the following way:

$\ce{2CH3COOH + CuO -> (CH3COO)2Cu + H2O}$

Nurdrage, on YouTube, did a video on it, and he did say that salt speeds up the reaction. However, he did not mention the way in which it sped up the reaction.

The same exact question is here

However, the answers did conflict and there was no clear correct answer. I am re-asking the question, in hope of getting a clear(er) answer.


texts: Colour changes in coordination complexes

texts:
What causes coordination complexes to change colour as they are heated? Do the ligands detach from the central metal or do the electrons held in the d orbitals leave? If both happen, which happens first?

Specifically, I am trying to explain the colour changes observed when potassium ferrioxalate $(\ce{K3[Fe(C2O4)3]})$ was heated. The colour change is from green-yellow to brown/red.


texts:
I'm looking at some data with substrate concentration on the $x$-axis and $k_\text{dep}$ on the $y$ axis. What does $k_\text{dep}$ mean? I understand that it must be a rate of some kind but what is the significance of the 'dep' part?

The data I'm looking at can be found in Fig. 9 in this paper (PDF):

Essentially this is a dose response curve for a substrate and enzyme. I suspect $k_\text{dep}$ is simply the rate but why $k_\text{dep}$ and not just $k$?


texts: Nucleophilicity/basicity in protic and aprotic solvents

texts:
In polar aprotic solvent, why is $\ce{F-}$ a stronger nucleophile than $\ce{I-}$?

What I think: If I talk about their basicity, $\ce{F-}$ would be more basic due to instability from its high electron density. Is it applied same when talking about nucleophiliicty?
Why is an atom with high polarizability a strong nucleophile?

What I heard: an increased atom size means a high polarizability, and a high polarizability means a high nucleophilicty because the atom can give its weakly-held $e^-$ easier.

What I think: above sentence makes sense to me. But in another point of view, isn't it also right that the atom with properties like that would be stable, making it poor nucleophile?
When talking about nucleophilicity, why does the polarizability matter in a polar protic solvent, but not in a polar aprotic solvent?

What I heard: when deciding the nucleophilicty of an atom in a polar protic solvent, there are two factors that come into play: solvation and polarizability.

What I think: in a polar protic solvent, since the effect of solvation is significant, the polarizability shouldn't mean so much. Rather, its effect should be significant in polar aprotic solvent since there's no hydrogen bonding. Is this wrong?


texts: Can electrons be present outside orbitals. If yes how does this affect chemical reactions

texts: In my physical chemistry textbook it is written (Or typed) that orbitals are regions where probability of finding electron is high (90%-100%). But since orbitals are regions of probability is it possible for electrons to be present outside orbitals for just a small number of atoms in a reaction if so how does this affect reactions that take place with these small number of atoms


texts: Does water freely absorb atmospheric CO2?

texts:
So, there has been a fairly groundbreaking new invention that can convert CO2 dissolved in water to Ethanol1. At face value, it's cheap, easy, and relatively energy-lightweight. All it requires is the catalytic surface and CO2 to be dissolved in water.

I'm just curious, this invention looks like the holy grail of Green news, but not being a chemist, and doubting that the reporters are (all) chemists, I have to ask "Where's the catch", and the best I can find is how quickly CO2 dissolves in water, so, is this step of the above process fairly easy, or would it require additional research?

Note: This question is about how quickly atmospheric CO2 dissolves in water. Comments on the discovery would probably be better served as a comment then an answer.


texts: Why is there only a slight change in pH when soda loses its fizz?

texts: I did an experiment for my chemistry class and did a control with sparkling water and the pH increased by a significant amount, but when done with sodas like cream soda, coke, or 7 Up, the pH change is so minimal that I can't say that there is a significant change in the pH level. Why do the pH level of these sodas to stay the same when they lose their fizz?


texts: Can you give examples for a halide ion reacting with interhalogen compound to give polyhalides?

texts:
Interhalogen compounds are formed when two halogens $(\ce{F},$ $\ce{Cl},$ $\ce{Br},$ $\ce{I})$ react together. They are represented by $\ce{XX'_n},$ where $\ce{X}$ is halogen of larger size and $\ce{X'}$ of smaller size. The total number of halogens in $\ce{XX'_n}$ depends on the radii of $\ce{X}$ and $\ce{X'}.$ The correct statement(s) regarding $\ce{XX'_n}$ is/are

  ❌ 1. $\ce{FCl3}$ is one of the stable interhalogen compounds.

  ✅ 2. Iodine can form an interhalogen compound containing maximum numbers
  of halogen atoms.

  ✅ 3. Interhalogen compounds are covalent in nature and more reactive than
  halogens, in general.

  ✅ 4. Halide ions reacts with interhalogen compounds to give polyhalides.

Regarding the 4th option: will it be like the following:

$$\ce{X'^- + XX'_n -> XX'_{n + 1}}?$$

Something like this? ($\ce{X}$ and $\ce{X'}$ are halogen compounds), so the polyhalide ion here would be $\ce{X'_{n + 1}}.$

What would be you views on this?


texts: Calculating ΔG at the extremes of reaction extent

texts:
This question follows on from a great post on comparing $\Delta_\mathrm{r} G^{\circ}$ to $\Delta_\mathrm{r} G$ answered here

The G vs ξ graph that is used in the answer is an excellent tool to understand how $\Delta_\mathrm{r} G$ changes with the extent of reaction:

If $\Delta_\mathrm{r} G$ is found on this graph by the slope of the line, what happens at the two extremes, where we have pure reactants on the left ($Q = 0$) and pure products on the right ($Q ⟶ ∞$)?

The equation to calculate $\Delta_\mathrm{r} G$ is: $$\Delta_\mathrm{r} G = \Delta_\mathrm{r} G^{\circ} + RT\ln Q$$

This would give  $\Delta_\mathrm{r} G ⟶ -∞$ (vertical slope asymptotic to the y axis) when $Q=0=ξ$ (i.e., when we have pure reactants). Logically, that would mean that absolutely pure reactants have infinite G (which doesn't seem right).

A similar problem occurs as we approach pure products: $\Delta_\mathrm{r} G ⟶ ∞$ when $Q⟶∞,ξ⟶max$ (vertical slope asymptotic to a line at ξ = max).

Can anyone reconcile this graph with the equation to calculate $\Delta_\mathrm{r} G$?


texts:
I have a PolyA tailing kit for putting PolyA tails on the 3' end of RNA. The kit comes with a proprietary 5X buffer and a 25mM MnCl2 solution, and in the standard set up I use 20uL of 5X buffer and 10uL of 25mM MnCl2. When trying to force the enzyme to accept an alternative substrate I did the reaction without the MnCl2 and it worked. Further research revealed that the enzyme also works with Mg++ ions, even though the rate is faster with Mn++, and some old papers on the enzyme mention using both Mg and Mn in the buffer. This leads me to believe that the buffer contains Mg++, but I don't know for sure because the manufacturer won't tell me.

I immediately thought I could use atomic absorption spectroscopy, but our department does not have one. I looked up colorimetric assays online, but the kits cost about $300, which is more than I want to spend on this idea. What I'm asking is if anyone knows a relatively simple method to detect magnesium in a solution? I have access to a UV-Vis spectrophotometer and fluorimeter.

EDIT: After digging for other phone numbers for the manufacturer I found someone who would tell me a little about the buffer, and it does contain magnesium. He couldn't me how much though. Spectro-Phone-otemotry.


texts: Calculating melting temperature of water with thermodynamical data

texts:
So at zero degrees celsius($\pu{273 K}$), for clean water, we have the equilibrium eq.:

$\ce{H2O(s) = H2O(l)}$

As it is at equilibrium, we know that $\Delta G = 0$. As we are dealing with clean water and clean ice we also know that $\Delta G_\text{standard} = 0$. (From the $\Delta G_\text{standard} =-RT\ln K$ relationship, where $K = 1$ results in $\Delta G_\text{standard} = 0$).

We also have the relationship:

$\Delta G_\text{standard} = \Delta H_\text{standard}-T\,\Delta S_\text{standard}$.

which we can re-arrange to:

$\Delta H_\text{standard}= T\,\Delta S_\text{standard}$.

And we can calculate $T$ which will be our melting temperature.

I found thermodynamical data for the reaction for $\ce{H2O(s)}$ and $\ce{H2O(l)}$, and got the equilibrium temperature to be $\pu{241 K}$! Which seems weird. What is wrong?

EDIT: I know that $\Delta H$ and $\Delta S$ aren't necessarily temperature independent, although I guess that is a prerequisite for the way I have done it?


texts: Dipole moment of (1s,2s,3s)-1,2,3-trichlorocyclopropane

texts:
Which of the following compounds has a zero dipole moment?

Only one of the options is correct
According to me, it looks like both options (c) and (d) are right. Since the dipole moments of option (c) molecule seem to negate each other (shown in the image below), so is option (d). However, only option (d) is right. Why?


texts: Melting post-1982 minted U.S. pennies and aluminum: Why does the slag turn blue?

texts: After melting aluminum inside of an iron crucible, I tossed in a handful of U.S. pennies that were minted post-1982. The slag began to burn a brilliant blue. What caused this?


texts: How do you know what inter-molecular interactions are present?

texts:
I'm studying for a chem exam and there are often questions of this form: What kind of inter-molecular interactions are important in (insert compound here). Then the possible answers are any combination of dipole-dipole, hydrogen bonding, and dispersion force.
My question is: When ever a molecule has hydrogen bonding does that mean there is also dipole-dipole?

How do you tell if a molecule has a dipole, for instance CH3COOH,  has one but how do you know?


texts: Why don't acyl chlorides give positive test with 2,4-DNPH?

texts:
In this post, Ron discusses the reasons why carboxylic acid derivatives such as amides, acids and esters do not give a positive result with 2,4-dinitrophenylhydrazine. He mentions that it is largely due to the fact that the carbonyl carbons in these compounds are not sufficiently electron-deficient to react with the hydrazine derivative due to strong conjugation within these compounds. What about acyl chlorides and possibly, acid anhydrides as well? These carboxylic acid derivatives are clearly rather electron-deficient, certainly much more so than aldehydes and ketones, as evident from their great ease of hydrolysis. Why don't they react with hydrazine to give hydrazone?

I think that the reason may be that $\ce {Cl^-}$ and $\ce {RCOO^-}$ may be good leaving groups that leave after the initial formation of the tetrahedral intermediate. In the case of acyl chloride, we may get a hydrazide instead of a hydrazone. This is likely the same for the case of acid anhydrides. Is my thinking correct?


texts: Question about the definition of an isotopes

texts:
My answer was as follows : atoms of the same element with differrnt relative atomic masses.

However in the mark scheme the answer was simply : atoms of the same element with different masses.

Was there something wrong with my answer?

Why does it matter?


texts: Reductive amination in case of secondary amines

texts: When an aldehyde or a ketone undergoes reductive amination when a primary amine is acting,the mechanism follows a pathway through hemiaminal and imine,what happens when a secondary amine is acting on the given carbonyl ? There will be no hydrogen on the amine nitrogen in this case to facilitate loss of water with the hydroxyl group of the hemiaminal.How does the reaction proceed then?


texts: What is the IUPAC nomenclature for Intermetallic Compounds?

texts: IUPAC has a system for naming organic compounds, ionic compounds, and inorganic compounds. I have seen something vaguely suggesting there is one for intermetallic compounds, such as: $$\ce{Fe-Co}$$ What is the system, if it even exists? If it doesn't exist what is the generally accepted way of naming intermetallic compounds?


texts: Can the concentration of a sodium carbonate solution be determined using volumetric analysis?

texts:
In the titration of sodium carbonate with hcl , isn't the first end point determined by phenol phthalene is equivalent to the volume of sodium carbonate

because my text book say thats the volume at the first end point is just half the sodium carbonate and the seconds end point is the whole sodium carbonate.

I know that at the first end point all the sodium carbonate all be converted to sodium bicarbonate but why shouldn't i stop here?!


texts: Why is the rate inversely proportional to the square root of temperature in Grahams Law of Diffusion?

texts:
In my book it is given that:

  The general form of the Grahams Law of Diffusion can be stated as follows when one or all of the parameters are varied:
  $$\text{rate} \propto \frac{PA}{\sqrt{TM}},$$
  where $P$ - pressure, $A$ - area of the hole, $T$ - temperature, $M$ - Molecular weight.

How can rate be inversely proportional to the square root of temperature? I feel that on increasing temperature it must increase, but how can the rate decrease?
Is the formula in my book correct or incorrect?


texts: Find the amount of atoms for a given mass

texts:
The atomic mass of two elements A and B is 40 and 80 respectively. If x g of A contains y atoms, how many atoms are present in 2x g of B?

I have tried to solve by assuming that

x g of A has y atoms
so x g of B has 2y atoms, because atomic weight of B is 2 times higher than A
so 2x g of B contains 4 y atoms.

But the answer key says it was wrong, the correct answer is y. What am I doing wrong?


texts: What does an equal sign mean in chemical equations?

texts:
I have been doing a bit of literature review, and have come across a few equations which use an equal sign (=) instead of an arrow, for example:

$$\ce{Fe^2+ + 1/2O2 = 2Fe^3+ + H2O}$$

What does the equal sign mean? Is the same as a single arrow $\ce{->}$ or the double arrow $\ce{<=>}$?


texts: Products of Reimer–Tiemann reaction of 4-methylphenol

texts:
p-cresol (4-methylphenol), undergoes the Reimer–Tiemann reaction upon treatment with chloroform ($\ce{CHCl3}$) in alkaline medium. Which of the following is the major and minor product?

  A. 2-hydroxy-5-methylbenzene-1,3-dicarbaldehyde
  B. 2-hydroxy-5-methylbenzaldehyde
  C. 4-(dichloromethyl)-4-methylcyclohexa-2,5-dien-1-one
  D. 4-(dichloromethyl)-4-methylcyclohexa-2,5-dien-1-ol

The answer given is that B is the major product, and C the minor product.

I have two questions about this:

Why is the mono-aldehyde B the major product, and not the dialdehyde A?
I think both electron-donating groups should greatly increase the reactivity of benzene, allowing the reaction to take place twice. On the other hand, steric factors would oppose the second formylation. I do not know which one predominates.
How can one derive the formation of the minor dearomatised product C?


texts: Why is meta-nitrophenol less acidic than para-nitrophenol?

texts: My professor said while explaining the acidic nature of phenol that meta-nitrophenol is less acidic than para-nitrophenol, and gave the reason that resonance doesn't play on meta, but I didn't get it.


texts: Sum of a rate constant gives the total decay rate

texts:
I want to ask a question about the sum of a rate constant to yield the total decay rate.

From previous studies, the rate of a reaction can be expressed evidently as

$$\ce{v_{rate} = k[A]}$$

where $\ce{A}$ is a molecule in a reaction.

I studied today about unimolecular photochemistry and that a molecule in its excited state $\ce{S_1}$ can do a number of processes:

Fluoresence (emit a photon and return to its ground state), $\ce{F}$
Intersystem crossing (convert to a triplet state and then relax), $\ce{ISC}$
Internal conversion (release heat to the environment and relax back to the ground state), IC
Photochemistry (be involved in a reaction), PC

and according to the lecture material, the total decay rate can be expressed as:

$$\ce{k_F + k_{ISC} + k_{IC} + K_{PC}}$$

i.e. the sum of the rate constants.

But I thought that from my studies, the total decay rate is expressed as:

$$\ce{v_{total \ decay \ rate} = (k_F + k_{ISC} + k_{IC} + K_{PC})[A]}$$

so why do I not include the concentration term as part of the total decay rate?

My thought was that $\frac{v_{\ total \ decay \ rate}}{[A]}$ is expressed as the total decay rate and hence it can be expressed as the sum of the rate constants, but I want to check that my logic is correct.

Why is the total decay rate expressed as a sum of all the rate constants of the expressions above?


texts: Is it possible to have an airborn fluorescent particle that reacts to lightning?

texts:
I want to measure the expansion of the atmosphere when it is heated and impacted by lightning, to have an idea of the propagation of sound waves made by lightning.

To do this, the ideal would be to have a box of static air which changes color or causes a durable fluorescence indicating the reaction of the electricity with the air and showing the patterns of expansion of air that has been heated by electricity.

Please can y ou suggest some chemicals which can be used to make the effects of lightning on air visible?


texts: Memory foam chemicals from pillow spoiled bed and rendered it useless

texts: I have recently purchased a memory foam pillow and in two days i ve experienced breathing problems and stomach problems and eyes irritation due to the harsh toxins in it and I returned the memory foam. But, The memory foam has touched the walls next to the bed and the plywood on the bed. Because of which i m unable to use the plywood which is still causing the harsh effects of the memory foam pillow whenever i m spending time on it. I recently bought another plywood it picked the same toxins ( may be from the wall) and i m again facing the same problem. Need suggestion for a way to clean these chemicals away from plywood and wall ?


texts: Mechanism of Bis-decarboxylation of α,β-dicarboxylic acid

texts:
According to an internal test series in FIITJEE, it was given that the following compound decarboxylates on heating,

I know that β-keto acids undergo decarboxylation on heating, but I was not sure about the above compound. So, on searching the internet, I found this post, Why are beta-ketoacids better at decarboxylation than gamma or delta? which seems helpful.
As, it says that for γ-keto acids or δ-keto acids, decarboxylation will most likely not happen with a beautiful explanation. So, I drew a possible mechanism and here's what I came up with:

With the help of the reasoning given by @TOLA3HPPA, I can say that decarboxylation will not happen as opposite charges are much separated, but I'm not sure about the mechanism.
Further, while searching on NIST Chemistry Webbook, I've seen an article named,

The Oxidative Bisdecarboxylation of α,β-Dicarboxylic Acids, J. Am. Chem. Soc., 1952, 74, 4370..

which possibly indicates that the above compound undergoes decarboxylation. So, if α,β-dicarboxylic acid undergoes decarboxylation, then what can be the possible mechanism?


texts: What will be produced when sucrose and potassium bitartrate react with each other?

texts:
What would happen if sugar and cream of tartar react with each other? Would it create an ester?

$$\ce{KC4H5O6 + C12H22O11 -> KC16H21O14 + 3H2O}$$

Is this correct? If not, why?


texts: Can Weinreb amides be used to form 1,3 dicarbonyl compounds?

texts:
Weinreb amides are useful in reducing acid chlorides (and esters) to form ketones due to the fact that the more reactive keto group is unmasked only after treatment with acid and water, which destroys the reducing agent. One example I have been given of use of Weinreb amides is the following:

We see here that the 1,3 dicarbonyl compound is formed. This implies that under these conditions, the ester lithium enolate does not attack the ester moiety in the Weinreb intermediate, presumably because it is not reactive enough. Is this a general case? If the ester was, say, replaced by a ketone, would we still form the 1,3 diketone species or would we have attack of this carbonyl centre to form an alcohol?


texts: Why are transition metals said to have different valencies?

texts: I understand that the term valency refers to the number of bonds an element would be able to form with either chlorine or hydrogen. If this is directly related to the number of valence electrons an atom has, why do transition metals have variable valencies?


texts: Heat of combustion of stereoisomers of 1-tert-butyl-2,4-dimethylcyclohexane

texts:
Which of the compounds below has the smallest heat of combustion?

I know that the heat of combustion is indirectly proportional to the stability of a molecule. And here both $\ce{CH3}$ and $\ce{C(CH3)3}$ are +I groups (inductive effect) but apart from that, I am stuck on how to compare these compounds.


texts: Why does Le Chatelier's principle work for temperature changes?

texts:
I do science tutoring. One of my students asked me why Le Chatelier's principle works, and I was able to explain it for concentration and pressure by referencing the law of mass action, but I could not figure out the reason why it works for temperature. I've been unable to find a compelling explanation online either.
To clarify, I understand how to apply the principle, but I do not know why it works.


texts: Why does SiH4 have unusually large bond angles?

texts:
The bond angles of $n > 2$ hydrides are usually around $90^\circ$, such as $\ce{PH3, H2S},$ $\ce{H2Se},$ $\ce{H2Te}.$ I understand that this is from increased $\mathrm{p}$ character in the bonding with these compounds.

However, for $\ce{SiH4}$ and $\ce{GeH4}$ the bond angles are actually quite close to $109.5^\circ$. Why do $\ce{Si}$ and $\ce{Ge}$ not typically use unhybridized $\mathrm{p}$ orbitals, and instead use closer to $\mathrm{sp^3}$ hybrid orbitals for bonding?


texts: Why does Brady's reagent include sulfuric acid and methanol?

texts: I'm supposed to explain why sulfuric acid and methanol are used in combination with 2,4-dinitrophenylhydrazine to form Brady's reagent. Are they just used as a solvent system for the hydrazine? Also, wouldn't sulfuric acid react with methanol?


texts: I've read an article that equilibrium exists when $G$ (Gibbs free energy) becomes minimum. If formation of products decreases Gibbs free energy, why won't the reaction proceed to completion so that Gibbs energy becomes minimum.


texts: Can ideal gas law be applied to water vapour?

texts: How to accurately estimate the molar concentration of pure water vapour at 298 K? Can ideal gas law be applied to water vapour to calculate the molar concentration?


texts:
I want to treat a wax so that it has an alkaline pH of at least 10. I tried just mixing sodium hydroxide with beeswax but the sodium hydroxide reacted with the beeswax and changed its properties. I want the wax to retain its natural properties and not be chemically altered by the pH-increasing component. How can I do this?

If it matters, the ideal wax for my purposes is carnauba wax which is a wax that comes from the leaves of a tree, but beeswax could work as well. It would be nice to have a method that would work for any kind of wax.


texts: Vapour density dependence on temperature

texts:
Does vapour density change with temperature or is it solely dependent on molecular mass
as per the formula VD=molar mass/2


texts: Cyclic Voltammogram - How to determine Overpotential

texts:
http://youtu.be/1f92vGOridg

Clicking on the link above will take you to a video with a diagram of a voltammogram.

Through my own experiments I have managed to obtain a similar diagram. However, I am unclear on how to determine the overpotential from such a diagram.

I know that the overpotential is simply the potential required over and above the amount required to get the reaction going thermodynamically.

If you could, please be explicit about what points I should choose exactly to make my calculation.

Thank you !


texts: What are the major differences between different reagents used for hydrolysis?

texts:
While doing questions on hydrolysis, i often get confused about what will happen if different reagents are used in hydrolysis... Such as H+ ; H+/H2O ; H+/H2O/heat ; etc.
What exactly can we concur when these different reagents are given?


texts: Mixture of products in ring opening epoxide reaction with acid

texts:
I ran across a question that says:

  In the following reactions, the result is sometimes one product, and sometimes a mixture of products. Design the mixture of products, explain why this is happening and predict what the main product is.

Since all of them are ring opening with acid reactions, I know that the nucleophile attacks the most hindered place. What it means by mixture of products? To draw the attack on the most and least hindered place and explain that the major one is the attack on the most hindered place, or there is a racemic mixture? And if so, why is that?


texts: Number of electrons in pseudo wavefunction and all electron wavefunction in pseudopotentials

texts: In pseudo potential theory most pseudo wavefunctions are specified to be the valence pseudo wavefunction. These pseudo wavefunctions are often compared with an all-electron wavefunction. My question is whether the all-electron wavefunction is the wavefunction for a valence electron as well. Also is the all-electron wavefunction a one electron wavefunction? Is the valence pseudo wavefunction a one electron wavefunction? Part of my confusion stems from the fact that some journals state that the charge of the pseudo wavefunction and all electron wavefunction have to be the same.


texts:
I have been writing a paper about polymers being "aged" by light. Most of this aging happens because light hits atmospheric oxygen and either excites it to its singlet state or causes atmospheric water to produce hydroxyl radicals. Either way, the $\ce{^1O2}$ or the $\ce{OH^*}$ causes some sort of radical mechanism which usually ends up with the polymer chain being cleaved or some $\ce{-OOH}$ group being attached on.

Anyway, that's not the important part for this post. What I am wondering about is: Should I be describing this as photo-oxidation or photo-degradation, or is either appropriate? In reviewing my paper I've noticed I constantly flip between the two. I know what I mean, but I'm worried somebody reading this will think I mean two different processes, or complain about it.


texts: After neutralizing a free radical, why don't anti-oxidants become free radicals themselves?

texts:
This is my understanding: A free radical is a molecule with a single unpaired electron. This molecule is highly reactive because it wants to steal an electron from another molecule (oxidation). Anti-oxidants are strong reducing agents that can donate their electrons to free radicals to neutralize them.
In order for this mechanism to be effective, the anti-oxidant should itself remain stable after the reaction. However, at this point the anti-oxidant would be missing a single electron. What general mechanisms keep them stable, so we don't get an endless chain of free radicals? Are there general mechanisms or do they each work differently (I know there are a huge amount of different anti-oxidants)?


texts: questions about half cell of Daniell cell

texts:
My questions are as follows:
For the Daniell cell, we assume that ZnSO4 and CuSO4 are 1M aqueous solutions. What if we use pure molten ZnSO4 and CuSO4 instead?

Assume that we prepare an isolated half-cell containing just a zinc metal bar immersed in a ZnSO4 solution, without any connection to any other half-cells (no salt bridge or wire).
Do you think the Statement below is true?
In the microscopic scale, a few number of Zn atoms of the metal bar are first oxidized to Zn2+ ions and while migrating to the aqueous solution leave their electron on the electrode. But since there is no way for the electrons of the electrode to migrate to, the accumulation of negative charge on the electrode and positive charge in the solution, force the  Zn2+ ions to reduce back to Zn on the electrode.
This process also occurs for an isolated half-cells of Cu-CuSO4. Is it true? Is it right to say that here, the first few Cu atoms oxide to Cu2+ ions and leave the electrode negatively charged.

What is the reason for the separation of the first few Zn atoms from the electrode and oxidizing as Zn2+? (What is the driving force?)
Why doesn’t just "neutral" Zn atoms separate from the electrode and migrate to the solution? Is it necessary for the Zn atoms to leave their electrons on the electrode and migrate to the solution as Zn2+ ions?

Is it possible that the Zn electrode, instead of releasing Zn2+ ions to the solution, adsorb Zn2+ of the ZnSO4 solution and accordingly the electrode get positively charged and the solution get negatively charged?
Does it occurs for Cu bar and the CuSO4 solution?


texts: Can I get ride of dichlorobenzene in honey?

texts:
I have some honey that was stored near dichlorobenzene crystals & has taken on the smell. I'm wondering if I turn it into mead if it would remove the chemical?

The procedure would be to add 5-10 parts water to the honey. Then boil the solution for at least an hour. I would think this should rapidly remove the benzine component.

The second part of the process would to be to add a yeast culture that would not ferment until the chlorine has dissipated.

It would seem that I could tell the chemical is absent when the strong odor is gone.


texts: How efficient is Zinc Acetate as an Oxygen absorber?

texts: I used to work in a microbiology lab and they used zinc acetate as O2 absorber for the anaerobic chamber. Was this an efficient way to scrub O2 from the air? I am asking because I want to make an N2 gas source by removing the oxygen from airflow. I only need to be able to produce at most 500 ccm of 99% N2. Is there something else I should consider?


texts: Why does my coffee creamer have titanium dioxide in it and is it safe?

texts:
From the manufacturers website of a coconut french vanilla coffee creamer:

  Ingredients: ORGANIC COCONUT MILK (WATER, ORGANIC COCONUT CREAM), DRIED CANE SYRUP, NATURAL FLAVORS, COLORED WITH TITANIUM DIOXIDE, DIPOTASSIUM PHOSPHATE, CARRAGEENAN, GUAR GUM.

My guess, from looking at the abstract of the report (which is behind a paywall), "Titanium Dioxide Nanoparticles in Food and Personal Care Products" is that the the metal is simply used for the (white) coloring. Is this all it is used for?

From the paper abstract:

  ... human exposure analysis to $\ce{TiO2}$ through foods identified children as having the highest exposures because $\ce{TiO2}$ content of sweets is higher than other food products, and that a typical exposure for a US adult may be on the order of 1 mg Ti per kilogram body weight per day.

Is there any potential risk (toxicity) to consumption of $\ce{TiO2}$ at these levels?


texts: Do chemists use molecular orbital theory to explain physical characteristics of a compound (i.e. melting point, boiling point, etc)

texts:
When you think of a molecule as simple as methane CH4, you can see that it has four identical C-H bonds. Carbon has 6 electrons, 2 in 1s, 2 in 2s and 1 in 2px, 1 in 2py and 0 in 2pz. Interestingly, one of the electrons in 2 s goes to 2pz. How does methane form 4 identical C-H bonds with just 1 s and 3 p orbitals? The answer is that carbon uses hybridized atomic orbitals called sp3 that has 25% s-character and 75% p-character.

Molecular orbital theory can explain why we have triple bonds. For example, ethyne. The sigma bond formed by the sp-sp overlap along with the two perpendicular p-orbitals that are parallel with each other that form 2 pi bonds explains the triple bond.

I've also noticed that unpaired sp3 bonds like those in ammonia (NH3) are used to form bonds and paired sp3 are the lone pairs.

I was wondering how any of this knowledge is useful for someone wanting to find out about the physical properties of compounds? Do chemists think about these things?


texts:
Im having trouble understanding Scatchard plots.
Y Axis = Bound/Free Ligand
X Axis = Bound Ligand
The graph has a negative slope.
Why when there is almost no Bound (Y axis = 0)  do we get a high positive number for Bound ligand on the X Axis corresponding to Receptor concentration? if there is no bound how is there a positive bound number?
it looks like the less bound ligand on the Y axis, the more bound on the X axis!


texts: Why is the rate of disappearance negative?

texts:
Rate of disappearance is given as $-\frac{\Delta [A]}{\Delta t}$ where $\ce{A}$ is a reactant. However, using this formula, the rate of disappearance cannot be negative.

$\Delta [A]$ will be negative, as $[A]$ will be lower at a later time, since it is being used up in the reaction. Then, $[A]_{\text{final}} - [A]_{\text{initial}}$ will be negative. Therefore, the numerator in $-\frac{\Delta [A]}{\Delta t}$ will be negative.

$\Delta t$ will be positive because final time minus initial time will be positive.

This means that $-\frac{\Delta [A]}{\Delta t}$ will evaluate to $(-)\frac{(-)}{(+)} = (-) \cdot (-) =(+)$

However, we still write the rate of disappearance as a negative number. Also, if you think about it, a negative rate of disappearance is essentially a positive rate of appearance. The reactants disappear at a positive rate, so why isn't the rate of disappearance positive?


texts: Can a bond be electrophilic or nucleophilic?

texts:
The indicated bond is:

A) Nucleophilic because it is electron-deficient.
B) Electrophilic because it is electron-rich.
C) Nucleophilic because it is electron-rich.
D) Electrophilic because it is electron-deficient.

The answer is D. I'm arguing with my friend because of this particular question.
I argued that there may be an error in this question. The arrow is pointing toward a carbon atom, so the question should be "The indicated carbon atom is:". But, if you take the question as it is, I answered C since I think that the "indicated bond" is the double bond, and is therefore nucleophilic and electron-rich. If it is not the double bond, then what is the indicated bond in this question? And is it possible for a single bond to be electrophilic?


texts:
I'm trying to make a diagram of the Pncn space group.

Firstly, I know that this space group belongs to the orthorhombic system and derives from the point group (2/m 2/m 2/m).

Therefore, although the abbreviated notation does not appear, this spatial group also has binary axes (which may be normal or helical).

We also know that the multiplicity of the space group is 8. That is, there are 8 positions equivalent to (x,y,z). Next, we try to determine them:

By the translation of the primitive lattice: (x,y,z)
As the point group 2/m 2/m 2/m/m is centrosymmetric: (-x,-y,-z)
For the plane type "n" perpendicular to the axis "a": (-x, 1/2+y, 1/2+z)
By the plane type "c" perpendicular to the axis "b": (x, -y, 1/2+z)
By the plane type "n" perpendicular to the "c" axis: (1/2+x, 1/2+y, -z)

If they were correct, I'd still be missing three positions. These three positions are given by the binary axes. Here I have a serious problem because I don't know if this binary axis is normal ($2$) or helical ($2_1$).

After making these deductions, I check to see if I've done well:

After that, I realise that some of the equivalent positions do not coincide with those I have deduced. For example, the two of the sliding planes of type "n".

I also have mistakes that I can't explain or understand. These are the following:

a) Why is one of the binaries at 1/4? I've searched the Internet and I can't find any explanation that helps me much.

b) Why is the plane type "n" displaced? I would have placed it on the line of axis "b".


texts: Why does H2O electrolysis produce O2 on the anode instead of H2O2

texts: If the oxidation of $\ce{H2O}$ produces $\ce{OH-}$ ions and the anode separates electrons from them leaving neutral $\ce{OH}$ molecules, why don't they bind to each other covalently?


texts: How can a dilute acid dissociate more than a concentrated one? (Ostwald dilution law)

texts:
According to Ostwald's dilution law, the degree of dissociation of an electrolyte is inversely related to the  concentration of it.

$$ \alpha = \sqrt{\frac{K_a}{C}} $$

This means that a dilute acid can dissociate more than a concentrated one. How is it possible? Please explain the physical meaning of this.


texts: Calculating the number of volatile molecules in a container of known volume

texts: Is it possible to calculate the number of volatile molecules (so only those in the gaseous phase) in a container of known volume, if the vapor pressure of the compound is known? So for example, if you have a container with a volume of $10\ \mathrm{ml}$ containing $3\ \mathrm{ml}$ of a Compound X with a vapor pressure of $10\ \mathrm{mmHg}$ at $\pu{25 ^\circ C}$, what is the number of gaseous molecules of X in the container?


texts: Transition of electron from HOMO to LUMO?

texts:
Molecules usually have certain number of (doubly) occupied molecular orbitals and an infinite number of unoccupied molecular orbitals but the probability of electron makes the orbitals shapes so, how LUMO (empty of electrons) orbitals exist despite no electron occupying it?

Also, when electron absorb sufficient energy will go excited from HOMO to LUMO, but is it allowed that the other electron still in HOMO will also go excited to LUMO leave HOMO without any electrons?


texts: What kind of chemical reaction happens when combining Tahini and Date syrup?

texts: While both Tahini and Date syrup are quite thin, when mixed together they form a paste-like substance that is very delicious, and quite thick. But what kind of chemical reaction leads to such sudden change in the viscosity of the mixture?


texts: I know that for atoms with big values of Z, relativistic effects have to be applied. Why does electron velocity increase with the increase of atomic number?


texts: Why do helium balloons expand in volume as they go higher?

texts: I realize as balloons go higher, the atmospheric pressure decreases, doing less to counteract the force of the gas particles pushing against the inner walls of the balloon. But at the same time, doesn't the outside temperature decrease, causing the gas particles in the balloon to lose energy and have less impactful collisions and a lower velocity? Is the reason why the volume nonetheless increases because the pressure outside decreases faster than the temperature? Or am I overthinking this?


texts: What kind of salts may I add in my GPC Eluent?


texts: What is a simple formula to approximate the change in relative humidity as temperature rises/falls?

texts:
The moisture-carrying ability of air goes up as the temperature rises. So if I take a volume of air and heat it or cool it (allowing it to expand/contract so the pressure remains constant) how can I calculate the (approximate) relative humidity of the warmer/cooler air that contains the same amount of water vapor?

Say I blow 30°c air at 20% relative humidity over a cool object (but not cool enough to condense water out of the air.)  The air is cooled to 20°. What would the relative humidity of the cooled air be if it contained the same amount of water vapor? How do I calculate that?

I am building an Arduino-based control for a warm air dryer for ski boots and bike gear. I will measure the temperature/humidity of the heated air as it comes out of the dryer, and then measure it again as it escapes the gear that I am drying. While the gear is still damp, the waste air should pick up additional moisture, and so its relative humidity should be higher that it would be if I simply cooled it down. When my gear is completely dry, the cooler waste air should contain the same amount of water vapor that it started with, so the relative humidity should be the amount calculated for the measured change in temperature.

I want a "good enough" solution, not one that's mathematically pure. If it gets me answers that are within a percent but involves less computation, that's better than an ideal solution that involves lots of time-consuming calculations. The Arduino microcontroller is fairly slow and cannot do high speed floating point calculations.

(Would this question be better on an engineering forum? I could see arguments either way.)


texts: I did an experiment in which I dissolved certain substances in water, measured the conductivity and compared that with the ion-radius. One of the things I dissolved was $\ce{NH4Cl}$. What should I use as the ion-radius  for $\ce{NH4}$, since it is not really one atom?


texts: Is it scientifically correct to call Diamond an element? Carbon has a wide range of allotropes, so would it be correct to actually just call graphite, diamond etc an element. For that matter, could we call any molecule containing only one type of atom, an element?


texts: Reaction of octahydroazecine with iodine crystals

texts:
I really don’t understand why the following reaction would take place first of all.

So this is a sub part of a question wherein we have to compare the basicity of the compounds formed through some reactions. So, I got the rest 3 of them but I have no clue about this one.

My concerns are..

Why would $\ce{I2}$ react in absence of any oxidising agent or catalyst?
Should the presence of $\ce{N}$ influence the reaction.
Is this reaction feasible?

  Ans -


texts:
I got this question in my exam:

Arrange the following in increasing order of acidic strength in gaseous phase
(i) $\ce{CH3CH2COOH}$ (ii) $\ce{CH3COOH}$

I felt that increasing order must be (i) $<$ (ii). But answer given is (ii) $<$ (i). Why will the order change in gaseous phase?


texts: What would be the aldol condensation products in B

texts:
In this question (13) I figured out A,C were wrong and D would be correct choice but I am stuck at finding out products formed in  B and also why it would be wrong?
Please help.


texts: Why does hand sanitizer leave your skin feeling cool?

texts:
I noticed, and perhaps many others have too, that the application of hand sanitizer (mainly ethanol), leaves one's hands feeling rather chilly after application.

What is responsible for this phenomena? Is it the high heat of vaporization of hand sanitizer? However, explanation doesn't hold water; water has a standard heat of vaporization of 40.65 kJ/mol while ethanol has a heat of vaporization of 38.56 kJ/mol.

Could it be the low boiling point of ethanol? Hand sanitizer disappears (vaporizes) within seconds upon rubbing the hands together. Water, however, does not.

Additionally, how does one square a high heat of vaporization with a low boiling point? If it takes a lot of energy to vaporize something, then how can that something have a low boiling point?


texts: Do all covalent nitrates on heating decompose to give nitrogen dioxide?

texts:
Being covalent we can conclude that they will on heating decompose completely, but will they give only $\ce{NO2}$ and not any other oxide is the question.
It is observed in $\ce{Pb(NO3)2, AgNO3,}$ and also $\ce{LiNO3}$ (the anomalous behaviour of $\ce{Li}$) that they decompose on heating to give $\ce{NO2}$ and the above mentioned nitrates possess good amount of covalent character. So as a rule can I remember that all covalent nitrates decompose to give $\ce{NO2}$ or there are any exceptions to it?


texts: Why are combustion reactions spontaneous?

texts: I learned that spontaneous reactions are reactions whose activation energies can already be overcome with the temperature they're already in. Since the temperature they're in already provides enough energy to overcome the activation energy, additional input of energy is not necessary and so it is a spontaneous reaction. So if this is true, why are some reactions like combustion reactions considered spontaneous if the temperature alone wasn't even enough to get over their activation energy? Is this definition of spontaneous wrong?


texts: I am currently pursuing a statistics course and I an interested in knowing how can statistics help this field in future. (I am interested because I love chemistry very much) Specifically, are there any open problems in chemistry which have remained as a conjecture or we have not been able to solve due to lack of adequate knowledge of statistics ?


texts:
I have a reference sheet for inorganic analysis which says that the confirmatory test for ferrous ions is as follows:

"Make a solution of the given salt (whose cation is to identified) and add potassium ferrocyanide [ potassium hexacyanidoferrate(II) ] solution to it.

If a dark blue precipitate is formed, then the presence of ferrous ions in the given salt is confirmed."

Chemically, what is the composition of this dark blue precipitate? Or is there a flaw in the test that I have specified?

If yes, then what is the real test and the chemical formula of the dark blue precipitate?


texts: Which definition of Acids and Bases conforms to the pH scale?

texts:
It's all in the title. Is it the Arrhenius or the Brønsted-Lowry definition? Or is it some other definition?

Also, our teacher told us that $pH$ stands for "Power of Hydrogen", but some sources say it is a number. So which it is?


texts: At what scenario will a LCD monitor that used mercury inside their lamp be harmful

texts:
Small amount of mercury and/or mercury vapors is harmful to human as it can cause damage to vital organs such as brain, heart and so on.

However, there are many electronic devices such as LCD monitor that used lamp that contain mercury for operation.

So, in what scenario will a LCD monitor that used lamp that contain mercury harmful?


texts: Does potential difference or current drive electrolysis?

texts:
Would a high voltage ( of the order of a few score kV ) drive electrolysis?

Or, does it require a large current and low voltage? Alternatively, does electrolysis require both large voltage & large current?


texts: Why don't electrons have the same spin even when in same orbit?

texts: Do electrons not have the same spin because that is just how it was found or does it contribute to another factor?


texts:
I am having difficulty in understanding the concept of torsional strain. Can someone explain it to me in a more elaborate manner?

I mean why should bond restrict movement in eclipsed conformation? Doesn't that make it unstable! I tried this Wikipedia article but I'm still having difficulty in understanding the concept.


texts: How many stereoisomers of octahydroquinoline are there?

texts:
I am trying to work out how many stereoisomers there could be of the following.

As indicated, I think there are two sites of varying the stereochemistry. The top site can have the hydrogen in different positions. However, can the bottom site be changed? I don't own a model set and so I am really struggling to see this!


texts:
How are poisons discovered? Does someone have to die/be poisoned from it first?

Or are there other ways of discovering the harmfulness of a substance? Perhaps everything is tested on other animals prior to testing them on humans?


texts: How can I find out how much caffeine is in my decaf tea and coffee?

texts:
I know that the decaffeination process is not perfect and that it leaves some caffeine. I've looked online and there was a company in 2009 that offered caffeine test strips but they seem to be no longer offered.
Another approach would be to use a GCMS, but used GCMS devices are expensive and it takes alot of effort to keep them in calibration (at least it did when I was in college).
Are there services where I can send a sample off and they will tell me how much caffeine they contain? Failing that, how would I reasonably test how much caffeine is in my tea and coffee?


texts:
Do 1s & 2s orbitals overlap of different atoms while forming sigma bond?
I think they should overlap as there will not be enough energy difference between them.


texts: CuS+HCl is it a reduction or oxidation reaction

texts: How do we identify whether a reaction is oxidation or reduction and please let me know whether the equation given above is oxidation or reduction.


texts:
What does this question mean by generally octahedral? Can this molecule adopt other shapes?

Also I have my suspicions about the Br-S-F bond angle being a perfect 180 degrees. Wouldn't vdW repulsions distort the bond angle and make it ~180 degrees? The way I see it, if we place the bromine axial, wouldn't its sheer size push down on the fluorines in the equatorial plane and thus distort the 180 degree bond angle?

On the other hand, now that I think of it, we only have one bromine pushing down on all the fluorines with an equal force and the net force should cancel out, making the 180 degree bond angle a theoretically perfect 180 degree bond angle.

Are there any ways to verify this other than jumping through hoops in one's mind? I tried making Marvin Sketch render the molecule but it wasn't useful (or I wasn't using it correctly).

Also, another choice I was doubting is choice 1. Are you sure there are 8 F-S-F bond angles < 90 degrees? I'm can see how the Br pushes down on the fluorines in the equatorial plane, creating four bond angles < 90 degrees. Where's the other four? Or are these from taking the Br to be in the equatorial plane?


texts:
What happens when diacetyl, that is, butan-2,3-dione is treated with acid?

I guess there would be acid catalysed aldol formation.
But what would the final product be? I can see too many possibilities. Please help me out here.

Thanks!


texts: What is the proper name for the but-1-ene's isomer methylpropene?

texts:
Give the name and draw the graphical formula of an alkene that is an isomer of but-1-ene and that has a different carbon skeleton.

I think it's 2-methylpropene, but I'm not sure whether the correct name is 2-methylprop-1-ene or 2-methylpropene.


texts: Why is tautomers not possible in benzoquinone?

texts:
1,4-Benzoquinone, commonly known as para-quinone, is a chemical compound with the formula $\ce{C6H4O2}$

When there are alpha Hydrogen's why can't it show tautomerism?


texts:
What I have got as (G) is this.

$\hskip1in$

My questions

How the rearrangement from (G) to $non-1-yne$ can happen i.e. its mechanism?
Why Sodium Amide in particular yield terminal alkyne, unlike the fused Potassium hydroxides why almost always yield internal alkyne?
Is there any limitation by how much this alkyne formation site can shift?

Please note that this is not my homework, I have done this question and I am interested in the mechanism.


texts: Ratios of produced gases in water electrolysis

texts:
I just did a little water electrolysis experiment at home by immerging two aluminum electrodes in water with a small amount of table salt. The voltage of the battery was 6 V.

What surprised me is that I was able to collect a much bigger volume of gas at the electrode connected to the - than to the + (about a factor 10 by eye). I would have expected a ratio of 1/2 (2 times more hydrogen than oxygen).

Why did I get less gas than expected at the electrode connected to the +?
Was the oxygen consumed by oxydising the electrode? (It appeared quite damaged at the end.)
How can I get a ratio of 1/2?


texts: Why did the Rio 2016 pool water turn green?

texts:
One of the swimming pools at Rio 2016 Olympics has turned green:

While proliferation of algae is a likely culprit, there have been some alternative explanations offered by local organizers. CNN has the following quote from a Rio 2016 official:

  A change in alkalinity

  Mario Andrada, the communication director for the Rio 2016 local organizing committee, says a sudden change in alkalinity is the culprit.

  "We expect the color to be back to blue soon," Andrada said, adding there is "absolutely no risk to the athletes or anybody."

How could a change in alkalinity occur on such a rapid time scale (a few hours)? And why would it directly change the color of the water? I can imagine that a more alkaline water could lead to precipitation of green metal hydroxide compound, but you would need a massive concentration of e.g. nickel to start with — does not seem very likely.
This article (http://www.independent.co.uk/sport/olympics/rio-2016-green-pool-drained-as-olympic-organisers-reveal-hydrogen-peroxide-is-cause-of-colour-change-a7189616.html) claims, that the treatment of the water via hydrogen-peroxide is what has caused the rapid change in the chlorine levels (which in turn made it possible for the algae to pollulate coloring the pool). Is this chemically possible? If so, how (or if not, why not)?
Also, the organizers claimed, that if was safe to enter the pool even after it had turned green. Was it really safe, or were the organizers lying about the hazards to cover up what they had done?


texts:
I have a vague memory of a question on the BBC panel game QI which started with a long chemical reaction equation on the screen, asking what it might be.

The answer was definitely "an explosion in a custard factory", due in part to high quantities of fine powders in the air, but also some of the chemical constituents of custard powder.

Does anyone know what that equation would be, or how I might re-find it?

How would one go about getting back from that equation to custard?


texts: Preference for basic conditions in ester hydrolysis

texts:
It has occurred to me that it is very common see the use of basic conditions for ester hydrolysis in various syntheses. One such sequence commonly seen in the case of the malonic ester synthesis is:

$\ce { OH^-,H2O}$
$\ce {H^+, heat}$

The first step is for the hydrolysis while the second step is for the decarboxylation. It is strange that there is a first step with basic conditions since ester hydrolysis and decarboxylation can both take place in acidic solution. Are there practical reasons for why ester hydrolysis is done with aqueous base?


texts: How to obtain curve energy and non-bonded interaction parameters (e.g. Lennard Jones parameters) with Gaussian?

texts:
I am parameterizing a force field and would need to obtain non-bonded interaction parameters of atoms (e.g., Lennard-Jones parameters).

My primary idea is to obtain a potential energy curve using the Gaussian 09 software and fit the data on that curve to an equation that has non-bonded interaction parameters of atoms (e.g., Lennard-Jones curve).

What I thought was to put two identical molecules and vary the distance between two atoms of these molecules (e.g., using the scan function on redundant coordinator editor) and, therefore, get the energy curve. What I was trying to do was a simple example to get interaction parameters for the oxygen atoms of two water molecules.

I was taking a test with Gaussian at the theory level B3LYP/6-311G++(d,p). Here is the input file:

%nprocshared=4
# opt=modredundant b3lyp/6-311++g(d,p) geom=connectivity

Title Card Required

0 1
 O                 -3.09468841   -0.10392610    0.00000000
 H                 -2.13468841   -0.10392610    0.00000000
 H                 -3.41514300    0.80100974    0.00000000
 O                  3.39491938    0.10392610    0.00000000
 H                  4.35491938    0.10392610    0.00000000
 H                  3.07446479    1.00886193    0.00000000

 1 2 1.0 3 1.0
 2
 3
 4 5 1.0 6 1.0
 5
 6

 B 1 4 S 10 0.200000

Something I noticed is that the level of theory used (obviously) influences the calculations results. In addition, the initial distance of the water molecules also influences whether the simulation will fail or not (in this example, it works).

Could you kindly tell me if this approach makes sense? Or should I use another software, another type of calculation? Do you have any suggestions on how I could get an energy curve by varying the distance of two non-bonded atoms in the Gaussian? Examples would be appreciated.

With Gaussian and a similar approach I was able to obtain parameters such as bond stretching, angle deformation and dihedral torsion. However, it would be lacking to obtain the non-bonded interaction parameters of atoms.

Things I should consider:

Do a rigid scan instead a relaxed scan (like the code presented).
I need a dispersion-corrected density functional methods.


texts: Why is the following reaction not considered a redox reaction?

texts:
The following question appeared in the Cambridge International AS and A level Chemistry Coursebook:

  Choose from redox, substitution, elimination, addition and hydrolysis to give the type of reaction for the following:
  $$\ce{C2H6(g) + 2Cl2(g) -> C2H4Cl2(l) + 2HCl(g)}$$

The answer given by the answer key was substitution since $\ce{Cl2}$ replaces $\ce{H2}$.

However, why is redox not a suitable word to describe the reaction? After all, the oxidation number of $\ce{C}$ in the reactants is $-3$, while it is oxidised to become $-1$ in the products. Furthermore, the oxidation number of $\ce{Cl}$ in the reactants is $0$ while it is reduced to $-1$ in the products.

Hence, by that logic, isn't the reaction also a redox reaction since $\ce{Cl}$ is reduced and $\ce{C}$ is oxidised?

Thanks in advance for any help.


texts: Synthesis of Schiff Bases in Aqueous Media

texts:
The paper https://www.hindawi.com/journals/jchem/2013/909217/ describes a possibility to synthesize salicylaldehyde-based Schiff Bases using water as a solvent. Yields shown for the microwave-assisted procedure are high, exceeding 90%, though the procedure requires no water removal, Dean-Stark equipment etc.

Is it the exception that proves the rule or the Schiff bases synthesis, in general, is always possible in aqueous media? Or maybe the microwave does the magic?


texts: Copper sulphate solution dissolves iron nail?

texts:
I tried an experiment of the Galvanic series and put three iron nails (slightly rusty, but brushed) into a copper sulphate solution and waited a few days until the nails get coated with copper.

Strangely something entirely different happened. The nails got almost dissolved, yet quite a bunch of residue added up.

I was not expecting this to happen. Could someone tell me what I did wrong?
Thank you


texts: Dissociation degree hell, Ostwald's law of dilution

texts:
Greetings dear chemists!

I got a nice exam problem on wich i am stuck for hours, well maybe the problem is with me. I know the problem can be solved. So here we go.

We got a weak monoprotic acid, we don't know its concentration, dissociation degree nor the dissociation constant. If we dilute it 3 times its volume, then the dissociated ions grow with an unknown constant, lets call it $y$. If we dilute the diluted solution again by 5 times its volume, then the dissociated ions grow 4 times. Whats the dissociation degree of the undiluted solution?

Yeah woah that looks tough. So lets give it my try.

Lets call the concentrations in order of dilution by $c_0, c_1, c_2$ and the dissociation degree by $\alpha_0,\alpha_1,\alpha_2$, and the dissociation constant of course $K_s$.

I managed to get three equations for this problem, but i feel i missed something or messed up my algebra someway i dont understand.

$$c_0=?,\alpha_0=?,K_s=?$$
$$\alpha_0=\frac{[A^-]}{c_0}$$
$$HA=H^++A^-$$
$$c_1=\frac{c_0}{3},\qquad c_2=\frac{c_1}{5} \to c_2=\frac{c_0}{15}$$
$$\alpha_1=y\alpha_0,\qquad \alpha_2=4\alpha_1 \to \alpha_2=4y\alpha_0$$
We call forth Ostwald;
$$K_s=\frac{c_0\alpha_0^2}{1-\alpha_0}\qquad \qquad \qquad \qquad (1)$$
$$K_s=\frac{c_1\alpha_1^2}{1-\alpha_1}=\frac{c_0y^2\alpha_0^2}{3(1-y\alpha_0)}\qquad \qquad(2)$$
$$K_s=\frac{c_2\alpha_2^2}{1-\alpha_2}=\frac{c_016y^2\alpha_0^2}{15(1-4y\alpha_0)}\qquad \qquad(3)$$
Equating the first and the second equation, i could get an expression for $y$. By setting $\beta=\frac{3}{1-\alpha_0}$ and ignoring the negative root
$$y^2+y\beta\alpha_0-\beta=0$$
$$y=\frac{-\beta\alpha_0+\sqrt{\beta^2\alpha^2+4\beta}}{2}$$
My problem starts when i equate the second and the third equation;
$$\frac{c_0y^2\alpha_0^2}{3(1-y\alpha_0)}=\frac{c_016y^2\alpha_0^2}{15(1-4y\alpha_0)}$$
$$5-20y\alpha_0=16-16y\alpha_0$$
$$11+4y\alpha_0=0$$
From wich i clearly see that im on the wrong track, since $\alpha_0$ and $y$ cant be negative, please help me on solving this nightmare. Maybe i missed something obvious, i dont really know that im on the right method to solve this either.


texts: Why is it that $\ce{(NH4)2CO3}$ smells while other salts with ammonium like $\ce{NH4Cl}$ does not smell? Does it have something to do with the equilibrium reaction? I know it has nothing to do with the coefficient of $\ce{NH4}$ in ammonium carbonate. I am pretty sure the water in our nose causes it to dissolve. I do note that $\ce{CO3^2-}$ is basic along with ammonium is acidic while the chloride ion is neutral. So does it have to do with the fact that $\ce{(NH4)2CO3}$ is more neutral than $\ce{NH4Cl}$?


texts: Why can one double bond exist in some resonance structures but two can't?

texts:
I am doing some biology and have not done chemistry in ages. I have two concepts I am struggling with.

When drawing Lewis structures, am I right in assuming that the central atom will always require covalent bonds to fulfil its octet before the outer atom's octets are filled?
For example when drawing lewis structures, the central carbon atom should be 'given' enough covalent bonds or lone electrons to have a full octet before lone electrons are allocated to the outer atoms in the structure.
I do not get why, for example, $\ce{HCO2-}$ can have resonant structures with one double bond (but not two double bonds) between the carbon and oxygens. (please see picture attached)


texts: Are the 2s and 2p subshells degenerate in the He+ ion?

texts: I know that the 2s and 2p (as well as 3s, 3p, and 3d) electron subshells are degenerate in the hydrogen atom. I was wondering if they are also degenerate in other one-electron species, such as the $\ce{He+}$ atom.


texts: reaction between Iron(ii) and Vanadium(v)

texts:
When we reduce Vanadium (V) using iron(II), why are we adding 85% Phosphoric acid?
After the above reduction, if we are going to titrate the mixture with Potassium permanganate, why are we adding dipotassiumpersulfate to the mixture before the titratioin?

  Here's the procedure:
  To 5 ml of vanadium (V) solution, add 2 ml of 6 M sulfuric acid, 1 ml of phosphoric acid and 0.20 g of hydrated ferrous sulfate to reduce vanadium (V). Then swirl the solution and allow it to stand for 3 minutes. Then add 0.23 g of dipotassiumpersulfate and let to stand for 5 minutes. Stir the contents vigorously and titrate with 0.02 standard potassium permanganate.


texts: Brillouin's Theorem: How do other determinants mix with the ground state?

texts: I am a bit confused about Brillouin's Theorem. I get that a singly excited determinant can not mix with the ground state wavefunction because that translates to an off-diagonal matrix element ($\langle \chi_a \chi_b|\mathcal H |\chi_r \chi_b \rangle$) and the Hartree-Fock eigenvalue problem requires off-diagonal elements to equal 0, but how about when a doubly excited determinant mixes with the ground state ($\langle \chi_a \chi_b|\mathcal H |\chi_r \chi_s \rangle$)? Both of them do not have $i=j$ thus both should be off-diagonal entries, yet a doubly excited determinant can mix with the ground state so what am I missing?


texts: EQPt pH of a Monoprotic Acid-Base Titration: Product of Molarites Over Their Sum

texts:
Context

The Henderson-Hasselbalch equation is as follows. $$pH=-\log\big(K_a\big)+\log\bigg(\frac{[A^-]}{[HA]}\bigg)$$ One may follow its derivation in order to understand how it came to be, yet there are still facets of it that the proof fails to explain. For instance, the equation provides mathematical evidence for why the pH at the midpoint of a monoprotic acid-base titration is equal to the $\ce{pK_a}$. Since $[A^-]=[HA]$ at the midpoint, the fraction reduces to 1. Because $\log(1)=0$, $pH=-\log\big(K_a\big)+0=-\log\big(K_a\big)$, which, of course, gives the pH at the midpoint.

My question is about the same sort of 'insight.'

My Question

Given A mL of B M HA with $\ce{K_a}=C$ titrated by D M xOH at 25oC, where HA is a monoprotic weak acid and xOH is a strong base akin to NaOH, the following expression equates to the pH at the equilibrium point (try it out on Example #1-e here!).

$$pH=14+\log\Bigg(\sqrt{\frac{B*D*10^{-14}}{C(D+B)}}\Bigg)$$

While deriving this, it became necessary for me to determine the $[A^-]$ (it is the major pH determining species at the EQPt). I reasoned as follows.

  To find the $[A^-]$, find the mmol of conjugate base and divide it by the total volume.

  Since the mmol of conjugate base is equal to the mmol of weak acid used, and the latter quantity is given by the initial volume of acid times its initial molarity ($A*B$), the former quantity is equal to $A*B$.

  The total volume, on the other hand, is equal to the initial volume plus what is needed to reach the equivalence point. The initial volume is given by A, so the expression will be $A+V_2$, where $\ce{V2}$ is what’s needed to reach the equivalence point. Take $\ce{M1V1}=\ce{M2V2}$ and plug in the given variables to get $B*A=D*V_2$. Solve for $\ce{V2}$ to get $V_2=\frac{B}{D}*A$. Substitute the value of $\ce{V2}$ into $A+V_2$ to find the total volume, or $A+\frac{B}{D}*A$.

  As mentioned before, divide the two expressions to give the final equation, listed below.

  $$[A^-]=\frac{A*B}{A+\frac{B}{D}*A}$$

However, the expression simplifies as follows.

\begin{split}
[A^-]&=\frac{A*B}{A+\frac{B}{D}*A}\\
&=\frac{A(B)}{A(1+\frac{B}{D})}\\
&=\frac{B}{1+\frac{B}{D}}\\
&=\frac{B}{\frac{D}{D}+\frac{B}{D}}\\
&=\frac{B}{\frac{D+B}{D}}\\
&=\frac{B*D}{D+B}\\
&=\frac{B*D}{B+D}\\
\end{split}

I find it interesting that such a complicated concept (at least to me) simplifies down to the product of two molarities over their sum. Similar to the way that I justified my initial expression and a facet of the Henderson-Hasselbalch equation, can anyone straight-up explain why this final expression yields the EQPt concentration of conjugate base in the given scenario? If it is possible to keep the answer to a relatively basic, non-organic point of view, that would be much appreciated!

Please note that I have done the best to explain what I am asking -- I think it is a legal but unordinary question for this site. If I can clarify, do not hesitate to comment!


texts:
Compound I is obviously the Z isomer. I thought it was obviously the less stable one too, given that there's a phenyl and t-butyl on the same side. The answer says that since the phenyl is planar, it actually exhibits less steric hindrance than a methyl group.

Is this because the planar phenyl ring can basically rotate its bulkiness away from the t-butyl, where as the methyl, while also free to rotate, always ends up with a hydrogen in the t-butyl's face?

Thanks!


texts:
There was a section about atomic orbitals in my organic chemistry textbook that I did not quite understand. First the author explained a bit about the Schrödinger equation, which I understood to be (vaguely, they did not go to any detail, even omitting the formula all together) a equation that describes the likeliness of positions of an electron in 3d space. $\Psi$ (i.e. the Schrödinger equation) can be solved for different quantum numbers that respectively represent the different orbitals.

This made me wonder what a picture (like below) of an orbital actually depicts, as it are chances that are described by $\Psi$, not boundaries. My best guess was that such picture represents an area that has a high chance, say 90% or more, of containing the electron (how they determine the shape, I don't know, but my best guess again here is that they only take those parts of the real orbital that add a significant percentage to the total chance of the electron actually being in the depicted orbital).

Are all these assumptions right?


texts: SN2: Neopentyl halides and methyl halides

texts:
Two part question for you. Let's preface this with I'm in organic chemistry 1, so we're just learning the basics of these reactions.

Are neopentyl halides completely inert to any reaction through any pathway, $\mathrm{S_N1, S_N2, E1, E2}$? For $\mathrm{S_N1/E1}$, even after solvolysis of the halide, is there too much steric strain there for anything to attack the carbocation? Even a small base like $\ce{MeO-}$?
Can a methyl iodide/bromide undergo $\mathrm{S_N2}$ with any basically any nucleophile since there's practically no steric hindrance? Even a bulky compound that's not very lewis basic like tButanol?


texts: Just curious, would mercury form an amalgam with gold that is already part of an alloy, i.e a gold platinum alloy?


texts:
Does anyone happen to know who was the first to use Hooke's law to model vibrational absorption peak frequencies/wavenumbers?

I know Hooke's law is first outlined here:

R. Hooke, Potentia restitutiva, or spring, in Lectiones cutlerianae, or a Collection of lectures: physical, mechanical, geographical, and astronomical, made before the Royal Society on several occasions ... to which are added divers miscellaneous discourses, ed. by J. Martyn (John Martyn, London, 1679), p. 4

But I'd like to know about whose idea it was to use it for spectra.


texts:
How can one predict whether a given complex ion will be square planar or tetrahedral when its coordination number is 4 using crystal field theory ?

Is it possible to theoretically predict this?


texts: High kinetic basicity of alkoxides compared to alkyls

texts:
I'm reading something at the moment where they state:

This reagent has enhanced basicity as it benefits from the high kinetic basicity of alkoxides compared to alkyls.

This is in the context of organometallics so we're talking about a negatively charged alkoxide ligand versus a negatively charged alkyl ligand.
So why do alkoxides have a higher kinetic basicity than alkyls? I thought this might be because the negative charge on $\ce{-O}$ is more accessible for doing the deprotonation than the neagtive charge on $\ce{-CH2}$ due to the bonded hydrogens. Is this correct or are there other factors at play?


texts: How do I show that a transition is magnetic dipole allowed with group theory/symmetry?

texts: I am taking an introductory course in symmetry and bonding and have so far learnt about SALCs and various point groups etc... one of my problems asks me to show a $\mathrm{^{2}T_{2g}\rightarrow\ ^{2}E_g}$ is allowed in a $\mathrm d^1$ metal. I am not sure how my knowledge of symmetry can help me answer this, all my searching flags up difficult quantum mechanics/group theory I don't understand! I think a relevant example I could use is $\ce{[Ti(H2O)6]^{3+}}$ as this is an octahedral, $\mathrm d^1$ system.


texts: Calculating the standard reduction potential for the oxidation of water

texts:
I was working with Latimer and Frost diagrams for oxygen when I came across what seems to me a contradiction.

From the Latimer diagram for oxygen below, we know the standard reduction potential for the reduction of $\ce{O2}$ to $\ce{H2O2}$ and the standard reduction potential for the reduction of $\ce{H2O2}$ to $\ce{H2O}$, as represented in the following chemical equations:

$$\ce{O2} \overset{+0.70}{\longrightarrow} \ce{H2O2} \overset{+1.76}{\longrightarrow} \ce{H2O}$$

$$\begin{align}
\ce{2H+ (aq) + 2e- + H2O2 (aq) &-> 2H2O (l)} & E^\circ &= \pu{+1.76 V} \\
\ce{O2 (g) + 2H+ (aq) + 2e- &-> H2O2 (aq)} & E^\circ &= \pu{+0.70 V} \\
\end{align}$$

If we add these two reduction chemical equations, we can find the standard reduction potential for the reduction of $\ce{O2}$ to $\ce{H2O2}$, which would be $\pu{+2.46 V}$ according to the aformentioned reduction potentials and chemical equations.

The reduction of $\ce{O2}$ to $\ce{H2O}$ is the reverse reaction of the oxidation of water:

$$\ce{2H2O(l) -> O2(g) + 4H+(aq) + 4e-}\qquad E^\circ = \pu{-1.23 V}$$

Why does the standard reduction potential for the oxidation of water calculated from the Latimer diagram differ from the value reported in the table of standard reduction potentials? More specifically, why is the value calculated from the Latimer diagram double of that reported in the table? I checked my work multiple times and do not understand why this occurs, but I might have still made a silly mistake.

References
Shriver, D. F., Weller, M. T., Overton, T., Rourke, J., & Armstrong, F. A. (2014). Inorganic chemistry 6th Edition.


texts: Calculating absolute internal energy of an ideal gas system

texts:
In the following derivation, I just calculated the absolute internal energy of an ideal gas as a function of its temperature. But my teacher said that we can never calculate the absolute internal energy in thermodynamics. Then how is the below proof correct?
Proof to calculate absolute internal energy:

We know that from the law of equipartition of energy, average energy ($E_\mathrm{avg}$) can be written as,
\begin{align}
E_\mathrm{avg} &= \frac{f}{2}k_\mathrm bT \\
E_\mathrm{avg}(n\, \mathrm{mol}) &= nN_A\frac{f}{2}k_\mathrm bRT \\
&=\frac{f}{2}nRT \tag{1}
\end{align}
Therefore, average energy for n moles of gas molecules is $\frac{f}{2}nRT$.
In case of an ideal gas,
$$E_\mathrm{total} = K.E$$
Since there are no interactive forces, $P.E = 0$ and other energies are negligible.
Therefore internal energy is equal to the kinetic energy.
From (1), we get:
$$U_\mathrm{ideal} = K.E_\mathrm{ideal} = \frac{f}{2}nRT$$


texts: electronic transition for polyenic molecules

texts:
I am having troubles with polyenes states symmetry.
I found an exercise on the pentadien, where they ask us to analyze the symmetry of the singlet excited states corresponding to:
State S1: π+ →π+
State S2: π+ →π-
State S3: π- →π+
State S4: π- →π-
1- I would like to understand what the signs + AND - refer to in this problem. Is there any forbidden transition?
I searched in plenty of books and I have not encountered  these signs, I thought that it corresponds to the wave function sign but I do not see the relation between the transition rules and the signs of the π MO, I thought +/- signs  matter only for transitions between Σ diatomic states .
2-In the case of a polyene molecule, in order to find the symmetry of the ground and excited states, do we need to find the symmetry of the π orbitals in relation to m and C2 operations only? or do we have to find the group symmetry of the molecule and apply all the operations of the groupe?
3-For an excited singlet state having two unpaired electrons, do we multiply the symmetry of the π molecular orbitals in order to get the symmetry of the state? Like m(S)*m(A)=m(A)? Can we do this?
4-Could you please help me and suggest books that are related to my questions?
Thank you all.


texts: Basicity of nitrogen heterocyclic compounds

texts:
Question :
The order of basicity for the following compounds is :

The logic I've applied is that since 4 has a conjugated system, the lone pair of N will be delocalised and hence would be the least basic. Conjugate systems/Resonance is not seen in the other three compounds
I'm not entirely sure about how to differentiate between the other three. For morpholine 2, If we see the stability of the conjugate acid formed, the O would exert (very less) -I effect, which should destabilize the positive charge on N (on formation of conjugate acid). Now between 1 and 3, 1 has a five other C atoms attached to the N, while 3 has four. Now CH3 is a +I group, hence more CH3 in 1 should stabilize the positive charge on N more than 3.
I don't think Inductive Effect should matter much, considering Inductive Effect becomes very ineffective with increase in chain length. But this is the only reasoning that strikes me. So ultimately, order of basicity becomes 4 < 2 < 3 < 1. Is my reasoning and the final answer correct?


texts:
We performed an experiment in class where we placed a piece of copper wire in a solution of silver nitrate, we were tasked with predicted the mass of copper that should react and the mass of silver that should be formed. My question is, what are indicators of Cu(I) and Cu(II) ions?

$$\ce{2 AgNO3(aq) + Cu(s) -> Cu(NO3)2(aq) + 2 Ag(s)}$$

I need to know this in order to calculate reaction yield and efficiency (whether the product is $\ce{CuNO3}$ or $\ce{Cu(NO3)2}.$


texts:
At the eutectic point, what is the effect on the melting point of adding impurities?

  Increase the melting point
  Decrease the melting point
  No effect on melting point

I know adding impurities decreases the melting point of a compound in comparison to the pure compound. But, the eutectic point is the lowest temperature where the new compound (the compound + impurity) melts. I'm indecisive between 1 and 3.


texts: When the NaOH deprotonates the hydrogen off the carbon, I thought there would be a resonance structure, with the negative charge being on both the oxygen and carbon. Since the oxygen is more stable with the negative charge, wouldn't the alkalation happen at the oxygen forming an ether? This is how i had the reaction occurring:


texts: Why does nitrogen molecule have greater ionization energy than nitrogen atom?

texts: I am studying an article in my book that $\ce{N2}$ molecule has higher ionisation than $\ce{N}$ atom and I have no clue it may be because of strong triply bonded atom then why this is not applicable to $\ce{F2}$, $\ce{F}$ and $\ce{O2}$, $\ce{O}$. Also explain and with reason for $\ce{N2}.$


texts: Nitrobenzene - Aromatic Substitution Reactions

texts:
Which EAS (electrophilic aromatic substitution) reactions does nitrobenzene show?

We know that nitrobenzene is particularly deactivated towards most such reactions, as the nitro group is strongly electron withdrawing via resonance and inductive effects. However, I wish to know exactly where to draw the line - which reactions nitrobenzene undergoes, and which ones it doesn't.

Of course, there's no clear boundary as to whether or not a compound undergoes a particular EAS, but can't we at least comment on the yield obtained in such reactions?

I haven't been able to find much about EAS reactions of nitrobenzene online, hence I come to Chem SE, seeking data and sources.

The reactions of interest are:

1.Friedel Crafts Alkylation, Acylation

2.Nitration (concentrated sulphuric and nitric acid)

3.Sulphonation (fuming sulphuric acid)

4.Halogenation in presence of Lewis acids
etc.

Please help! Thanks a lot!


texts: Why is the more substituted C-atom attacked in oxymercuration-demercuration?

texts:
In hydration of an alkene by oxymercuration-demercuration , for an asymetrical mercunium ion, the more substituted carbon atom is attacked by water

Why is this the case?
Since R groups are electron donating, it should make the more substituted carbon less electrophilic but the reverse is true.


texts: I have used data from a question regarding the reciprocal wavelengths observed when lithium transitions from excited states to a common ground state. The lowest energy transition is from n=3 to n=2. The question goes on to say that this lowest energy transition, in high resolution, has 7 peaks, and asks for an explanation as to why there are not 8 lines. Can I have some guidance on this? I think spin-orbit coupling is relevant. I am aware that the dipole moment of an orbiting electron interacts with a magnetic field (from the orbital angular momentum of the electron?) and so some orbitals are raised/lowered slightly, those with an "l" greater than 0.


texts: Relationship between a temperature increase of an exothermic reaction, Keq, and kf (forward rate constant)

texts:
I'm currently stuck on problem #30 for the Chemistry Olympiad 2015 local exam which reads:

For a reversible exothermic reaction, what is the effect of increasing temperature on the equilibrium constant ($K_\mathrm{eq}$) and on the forward rate constant ($k_\mathrm{f}$)?
(A) $K_\mathrm{eq}$ and $k_\mathrm{f}$ both increase
(B) $K_\mathrm{eq}$ and $k_\mathrm{f}$ both decrease
(C) $K_\mathrm{eq}$ increases and $k_\mathrm{f}$ decreases
(D) $K_\mathrm{eq}$ decreases and $k_\mathrm{f}$ increases

The answer for this problem is D.
My approach:
To find the relationship between $K_\mathrm{eq}$and $k_\mathrm{f}$, I first used this theoretical reaction of
$$\ce{A -> B + \mathrm{heat}}$$
The forward rate can be defined as
$\mathrm{rate(f)} = k_\mathrm{f}[\ce{A}]$
and the backwards rate as
$\mathrm{rate(b)} = k_\mathrm{b}[\ce{B}]$
Since we're finding the relationship between these rates with $K_\mathrm{eq}$, rate(f) = rate(b) because the reaction is at equilibrium. This allows the equation
$k_\mathrm{f}\ce{[A]} = k_\mathrm{b}\ce{[B]} $
to be set up. Dividing both sides by $k_\mathrm{b}$ and [A] gives us
$k_\mathrm{f}/k_\mathrm{b} = \ce{[B]/[A]}$
And
$K_\mathrm{eq} = \mathrm{ products/reactants }= \ce{[B]/[A]} = k_\mathrm{f}/k_\mathrm{b}$
Due to the fact that the temperature is raised with an exothermic reaction, the reaction is reactant favored and more A will be formed. Since
$K_\mathrm{eq} = \mathrm{ products/reactants }= \ce{[B]/[A]}$
$K_\mathrm{eq}$will decrease. However, why doesn't $k_\mathrm{f}$ decrease? Since
$K_\mathrm{eq}= k_\mathrm{f}/k_\mathrm{b}$,
how could $k_\mathrm{f}$ increase while $K_\mathrm{eq}$ decrease if they're equal to each other in that equation? Shouldn't $k_\mathrm{b}$increase or $k_\mathrm{f}$ decrease to "=" to the decreased value of $K_\mathrm{eq}$?


texts: What is the mechanism of endothermic dissolution?

texts:
My real question is in fact "How can dissolution happen if it's endothermic?" However, there
have been many questions regarding this exact topic and the answers about Gibbs free energy
determining spontaneity of the reaction doesn't help my intuition at all. The majority of answers
list the increase of entropy as the cause of endothermic dissolution, but in my opinion, entropy
doesn't make sense as the cause.
Let's take a similar problem, namely the melting of a solid. If we place a solid with lower
temperature into surroundings with higher temperature (enough for the solid to reach its melting
point), it's not that liquification would cause the temperature of the surroundings to drop, but
rather that the transfer of heat from the surroundings to the solid would cause liquification. The
acquired heat allows the solid to increase its entropy, not the other way around.
So, if increased entropy is the result of endothermic dissolution, what is the cause? Or, what is
the mechanism that allows entropy to be increased?
Let's take the dissolution of NaCl in water as an example. This process is endothermic by around
4 kJ/mol. My guess is that, since some ions in the solid have higher kinetic energy than average, this energy
will be sufficient to overcome the 4 kJ/mol barrier and leave the solid, taking some of its thermal
energy away from it. As a result, the temperature of the remaining solid will drop a little. Since
the temperature of the solid is now slightly lower than the temperature of the surrounding water,
heat will be transferred from the water to the solid until the temperatures are equal. This will
result in lowering the temperature of water and in the increase of entropy.
Is my thinking correct? If not, why?


texts: Does the main washing effect of soap come from foam?

texts:
I am curious if the main cleaning effect of soap comes from its foam (or, maybe, it is just a by-product).
Here are some  points, that might clarify what I mean:

Does foam sort of "carry" dirt and germs away from the surface?
If it is not the "main motor", which makes the soap function: is it possible to make a soap which will still be as effective without it producing any foam?
What percent of the cleaning work, if any, does foam undertakes (i.e. how effective would soap be against germs and dirt without its foaming ability)?


texts:
I have a homework problem where I'm to draw the structure of a compound of molecular formula $\ce{C10H12O2}$ using the following IR data and $^1$H NMR spectrum:

IR absorption at 1718 cm$^{-1}$

NMR Data:

Triplet (3H) at ~1.4 ppm

Singlet (3H) at ~2.4 ppm

Quartet (2H) at ~4.3 ppm

Doublet (2H) at ~7.2 ppm

Doublet (2H) at ~7.9 ppm

The two doublets lend to a disubstituted benzene. The IR absorption lends to a C=O.

I came up with this structure:

My thoughts were that the singlet owing to $\ce{CH3}$ would be shifted to the left of the other $\ce{CH3}$ due to the C=O.

However, I'm incorrect. This is the correct answer:

What makes this answer more correct than mine (other than the fact that it's an ester and we happen to be studying esters)? Thank you for any help you can offer.


texts:
if a gamma ray hits an electron and transfers energy, does it hit that electron (ionising the atom), transfer all its energy and stop or does it pass through multiple electrons, transferring a portion of its energy each time?

i.e.) if a gamma ray has enough energy to ionise multiple atoms, will it, or will it just give all its energy to the one electron?

also if is has the energy to ionise multiple atoms, about how many electrons can it remove (for a range of ray energies)? (i know it is a bit general, but lets say for the first ionisation of potassium)

also, why is the dose equivalent so low? is it because it can only ionise 1 atom by +1, or because its ionizations (and hence energy) are dispersed throughout many atoms (making the meaning less energy transferred per ionisation)?

(i know this has a lot to do woth physics and so i posted it on the physics SE to, but i was wondering weather a fellow chemist could help me out, thanks)


texts: Why are non-aromatic rings more stable than anti-aromatic ones?

texts: Is there any non-quantum explanation to the greater stability of non aromatic compounds as compared to  anti-aromatic compounds?


texts: Our lab is doing aqua regia digestion of an ore matrix for the determination of Platinum Group Elements (PGE). We're getting white smoke when we run it through a Graphite Furnace assisted Atomic Absorbance Spectroscopy (GFAAS). Smoke forms above 1000 C, so we think it's some metal evaporating. Any thoughts or ideas? Thanks in advance!


texts:
I was given initial concentrations for the following reaction:

$$\ce{2SO2 + O2 <=> 2SO3}\ \ \ K_c =7.5\times 10^{-2}\\
[\ce{SO3}]= 0.05\ \mathrm{M}\\
[\ce{SO2}]= 0.125\ \mathrm{M}\\
[\ce{O2}]= 0.02\ \mathrm{M}$$

What are the final concentrations?

First I calculated $Q$, and found that $Q>K_c$ so the reverse reaction is favoured.

I created an ICE table and wrote the expression for $K_c$ to solve for $x$, but the calculator says there is no solution.

Here is the ice table:

$$\begin{array}{|c|c|c|c|} \hline
\ & [\ce{SO2}] & [\ce{O2}] & [\ce{SO3}]\\ \hline
I & 0.125 & 0.02 & 0.05 \\
C & +2x & +x & -2x \\
E & 0.125+2x & 0.02+x & 0.05-2x\\ \hline \end{array}\\$$

$$7.5 \times 10^{-2} = \dfrac{(0.05-2x)^2}{(0.02+x)(0.125+2x)^2}$$


texts: Finding equilibrium temperature when two things are mixed

texts:
10 g of ice at −10 °C is added to 10 g of water at 85 °C. What is the final temperature and amount of ice left in the system? (System is kept inside an ideal insulator)

This question may seem quite easy for many of the readers, but please help me with such questions as I find them tricky. I understand that this is a question which involves the application of the $Q=mc\,\delta T$ formula and that we have to equate the $Q$'s of both ice and water in order to obtain the answer.
Another thing which is troubling me is that the answers to most of such questions that I have encountered is 0 °C, and this question is not an exception.
Please suggest me on how to go about such questions, and provide some conceptual clarity on the topic if possible.


texts: Why is carbon monoxide not a greenhouse gas?

texts: Carbon monoxide is considered to be a toxic gas and, given that it is usually found along with $\ce{CO2}$, why it is not considered a greenhouse gas?


texts:
What exactly is the difference between the following equations?
$$p = kx \qquad\text{and}\qquad m = kp$$
Is the $k$ in both same, because I have seen same $k$ in textbooks for both equations?


texts: Why is the acetate ion considered a monodentate ligand as opposed to a bidentate ligand considering both oxygen atoms can donate their respective lone pair of electrons?


texts:
For the last assignment of the school year, my science teacher gave the class questions about chem, physics, etc. The third question had me confused and I'll be thankful for all the help given. The question is:

An ionic solution is created and tested to see how much current can go
through it. Two groups are told to create the following solution
consisting of $\pu{1.0 +/- 0.1 L}$ of water and $\pu{2.0 +/- 0.2 g}$ [of what?] . The battery used for the test is $\ce{8 +/- 1 V}$.
Group A measures a current of $\pu{2.1 +/-0.1 mA}$.  Group
B measures a current of $\pu{3.4 +/- 0.1 mA}$.
Describe 3 possible reasons why Group B measures a current greater
than group A.