texts:
The following reaction seem to be valid;
$\ce{CH2OH-CHOH-CH2OH ->[HIO4]CH2O + HCOOH + CH2O + 2H2O}$
Apparently, there are similar reactions by 2,3-dihydroxypropanal, and also by the straight chain form of fructose.
The first two reactions involve doing the Malaprade reaction on molecules with adjacent alcohol and aldehyde groups, and the last one involves doing it on a ketone. Both times, it seems sufficient to just cleave the carbon-carbon bonds and oxidise each resulting molecule one step up the ladder.
As far as I know, the Malaprade reaction is for vicinal diols, and I can't stretch the mechanism to work for carbonyls.
Can anyone help me with how these reactions work?


texts:
I bought different kinds of acid for experiments and home usage that I stored in secured containers into an IKEA cabinet.

I just realized that despite the fact that all the containers are properly closed, the metal parts of the cabinets are completely rotten. I am quite surprised because there shouldn't be much vapor in there.

What is the correct way to store acids at home? Should I purchase some specific container? How can I prevent vapors from escaping? Perhaps the problem is somewhere else and my containers are not good enough for my acids.

The acids I have: $\ce{H2SO4}$ (30%), $\ce{HCl}$ (32%), $\ce{H3PO4}$ (85%), $\ce{HNO3}$ (10%), $\ce{CH3COOH}$ (98%).

Note: the chemicals are actually stored in my electric/electronic workshop which is a separate room at home and always locked when I have visitors.


texts: Suitable coating material for protection of sensors

texts:
I'm building a moisture/temperature sensor for outdoor use in soil. It uses capacitive sensing for moisture and an NTC thermistor for the temperature. It's going to be used for vegetables so food safety is a concern.

I don't think the PCB is food safe, or safe from corrosion/degradation due to the soil and moisture would creep into the FR4 material in the PCB and cause my measurements to drift so I would like to coat the entire thing to protect it from the elements, keep my vegetables free from toxins, and keep the measurements from drifting.

So these are the requirements in order of importance for the coating:

Not electrically conductive
Food safe
Doesn't degrade/react in/to soil/sun light
Hydrophobic
Resistant to abrasion when insertion/removing from the soil
Affordable
Low relative permeability (electromagnetic)
Decent thermal conductivity
Not a host for bacteria

I first considered a food safe epoxy but I had difficulties finding a reputable supplier of food safe epoxies in Germany (my German sucks). I did find a supply of food safe silicone which is nice in that it has all the properties above but I could only find it in large quantities and it's quite expensive. I also considered L/HDPE which seems to have all the criteria apart from the bacterial aspect (I'm not sure about that) but it seems like melting it to have a low enough viscosity to be able to form a solid but thin coating seems hard/impossible.

My knowledge on the topic of epoxies, plastics, rubbers and chemistry in general is limited, so I'm turning to chemistry@sx for recommendations to what I can use for a coating and what process to use for coating. And maybe I've misunderstood something of the materials I've considered so far... Also I'm sorry if this is the wrong place for this question, I'm not sure where else to post.


texts: Application of limiting reagents and acid-base stoichiometry

texts:
I'm having a bit of trouble with the latter questions of this problem.

  $\pu{15.0 mL}$ of $\pu{1.4 M}$ $\ce{HCl}$ was mixed with $\pu{1.00 g}$ of $\ce{CaCO3}$ until all the solid had dissolved. The solution was then transferred to a conical flask and made up to $\pu{200 mL}$ with water. A $\pu{20.0 mL}$ portion of this solution was then neutralized by $\pu{8.50 mL}$ of a $\pu{0.100 M}$ $\ce{NaOH}$ solution.
  Calculate:

  Amount of substance in excess of $\ce{HCl}$ in the $\pu{20.0 mL}$ portion
  Amount of substance in excess of $\ce{HCl}$ in the $\pu{200.0 mL}$ portion
  Amount of substance in excess of $\ce{HCl}$ which reacted with $\ce{CaCO3}$

My approach

$$\ce{2HCl(aq) + CaCO3(s) -> CaCl2(aq) + H2O(l) + CO2(g)}$$

Finding the amount of substance of each reactant and hence the limiting reactant,

For $\ce{HCl}$:
\begin{align}
M[\ce{HCl}] &= \frac{\mathrm{mol}}{\mathrm{L}}\\
\mathrm{mol}[\ce{HCl}] &= \mathrm{M}\times \mathrm{L}\\
\therefore \mathrm{mol}[\ce{HCl}] &= 1.4\times (15.0\times 10^{-3}) = 0.021
\end{align}

For $\ce{CaCO_3}$:
\begin{align}
\mathrm{mol}[\ce{CaCO_3}] &= \frac{\mathrm{m}}{\mathrm{mm}}\\
\mathrm{mol}[\ce{CaCO_3}] &= \frac{1.00}{100.0869 }\\
\therefore \mathrm{mol}[\ce{CaCO_3}] &= 9.9913\times10^{-3}
\end{align}

Therefore (after dividing by stoichiometric coefficients) $\ce{CaCO_3}$ is limiting.

From here I'm not sure if what I did next is correct. I found the amount of substance of $\ce{CaCl_2}$ produced the remaining $\ce{HCl}$ in excess. Which were,

\begin{align}
\mathrm{mol}[\ce{CaCl_2}] &= 9.9913\times10^{-3} \text{ and,}\\
\mathrm{mol}[\ce{HCl}] &= 1.1009\times10^{-2}
\end{align}

(Meaning that we have $9.9913\times10^{-3}\mathrm{mol}$ of $\ce{CaCl_2}$ and $1.1009\times10^{-2}\mathrm{mol}$ of $\ce{HCl}$ in in $\pu{15 mL}$ of solution?)

From here on I'm stumped.


texts: How can semi-permeable membrane be so smart?

texts:
According to the definition, a semi-permeable membrane is a membrane that allows only solvent molecules to pass through it; solute molecules are blocked.  Solvent molecules flow from the membrane side that has low solute concentration (i.e. high solvent concentration) to high solute concentration (i.e. low solvent concentration).

Lets take a case:

I take oil as a solvent in one side and water as a solvent in other side. I take the same solute in both sides.
Initially, the water side is filled to height $h$ and the oil side to height $2h$. The amount of solute is same in both the sides. So the solute concentration is more in water than in the oil.  Accordingly, oil will flow from the oil side to water side. Now, I add more water on the water side to reduce the solute concentration on the oil side.  Accordingly, water should now flow towards the oil side.

So what will happen? Will this happen? What makes the semi-permeable membrane so smart or intelligent?


texts: Why don't molecular orbitals change when electrons are added or removed from a molecule?

texts: My lecturer says that molecular orbitals don't change when electrons are added or removed from a molecule, but I don't understand why. As electrons are described by wave functions, surely more or fewer electrons means that the electrons interact differently and consequently the atomic orbital wave functions interact i.e. interfere differently to form different MOs.


texts: Cleaning with Vinegar - what surfaces does it react badly with? Metal window sills ok?

texts:
I'm cleaning up some mould around the home and I have some substance on my window sills which I'm not quite sure if it's dirt or mould.

I have read about using Vinegar to clean up mould, but an article I was reading awhile back said you shouldn't use Vinegar on certain things as it can eat away at it or something because it's acidic; I thought this may have been metal and/or painted substances but I may be wrong.

I know you shouldn't use it on granite, marble and natural stone, but was wondering if using it on the painted metal window sills is ok or should I use something like diluted Tea Tree Oil instead, or would that be too oily?

FYI I would be using White Vinegar.

Here is a pic of my window sills:


texts: Why does an element's chemical properties rely only on its valence electrons and not on anything else?

texts: I understand that elements use their valence electrons for their reactions and whatnot, and that the whole idea of the electron-dot structure is all about valence electrons. But why can't the other electrons play a part in it?


texts: What is the temperature needed for a reflux using a mix of solvents as the reaction medium?

texts:
I had a quick query regarding the setup of a reaction. The procedure that I am working from states that I need to put my reaction mixture under reflux for 3 hours. The solvents used are diethyl ether (30 mL) and THF (10 mL). How do you determine the temperature needed? Do I go via the boiling point of diethyl ether or THF?
If more details are needed regarding the reaction I am carrying out then please let me know. But my query leans more towards the determination of mixed solvent systems in general and how one would determine the reflux temperature needed.


texts: Why is the ground state electronic configuration of Group 10 (Ni group) elements so anomalous?

texts:
While studying about d block elements I came across this table showing outer shell electronic configuration of group 10 elements

$\ce{Ni}$ $ $ $ $ $ $ $ $ $ $  $3d^8$ $4s^2$
$\ce{Pd}$ $ $ $ $ $ $ $ $  $4d^{10}$ $5s^0$
$\ce{Pt}$ $ $ $ $ $ $ $ $ $ $ $5d^9$ $6s^1$

(Source Concise Inorganic Chemistry, JD Lee, adapted by S. Guha Pg 563)
Now I cannot understand the reason behind this. If we consider that $\ce{Pd}$ has changed its config. to attain stability then what's wrong with $\ce{Ni}$ and $\ce{Pt}$? And should the outer shell electronic configuration of the ground state not be same in elements down a group?
Edit
To those who have marked my question as a duplicate of the one mentioned, I humbly request to explain me which answer to the above mentioned question (of which mine is marked as a duplicate of) tells about the anomalous behavior of group 10 elements and why $\ce{Zn}$ assumes $d^{10}$ config and none of the others in the group do the same and again $\ce{Pt}$ assumes a $5d^9 6s^1$ config, while $\ce{Ni}$ does not. Also please do point out  where can I find an answer to why in this particular group there is no similarity in ground state electronic configuration b/w elements of the group. Thank You.


texts: What exactly is pairing energy when electrons are paired in orbitals and what is responsible for it.


texts:
I read this sentence in a paper (J. Phys. Chem. A 2014, 118 (20), 3678–3687. DOI: 10.1021/jp502475e):

  Calculations using Hartree–Fock theory systematically overestimated
  dipole moments and underestimate polarizabilities.

Is there any intuitive explanation that the HF approximation affects dipole moments and polarizabilities differently?


texts: Is it possible to improve electrolysis rate without increasing heat?

texts:
I'm separating water into hydrogen and oxygen by connecting a DC current to 99.9% pure nickel electrodes in a solution of NaOH in deionized water.

It works great, except that any attempts to increase the rate of production by increasing current, increasing NaOH, bringing electrodes closer together, etc. also result in an increase in heat.

At the moment the bottleneck for my production rate is trying to keep the water from boiling or otherwise causing heat damage to the apparatus.

I've considered investing in a cooling system, but I'm also interested in knowing whether or not it is possible to somehow improve the efficiency of the electrolysis and thereby improve separation rate without increasing heat.

(In case you're wondering, I'm using hydrogen to fill balloons.  It works quite well, I can fill a normal sized balloon in a few minutes, but then I need to wait an hour for everything to cool down.  (Yes I know hydrogen and fire don't mix well.))


texts: Pressure change when volume and temperature both increase

texts:
By what factor does the pressure change if:

the temperature rises from 0 to 100 degrees Celsius,
and the volume is doubled?

$$
\pu{0 °C} = \pu{273.2 K}\\
\pu{100 °C} = \pu{373.2 K}
$$

Assuming $pV = nRT$:

Since pressure is proportional to temperature, neglecting the change in volume, the pressure would increase by a factor of $$\frac{373.2}{273.2} = 1.366\ .$$

Now since the volume is doubled as well, can I simply conclude that the pressure increases by a factor of $$\frac{1.366}{2} = 0.683\ ?$$

This is a task from a introduction to gases, I've mainly used the ideal gas law $pV = nRT$, but I wanna make sure my logic isn't flawed from the beginning.


texts: Electronic configuration of the actinides

texts:
I was reading about actinides and I need some help in understanding this paragraph from Concise Inorganic Chemistry by JD Lee -

  The electronic structures of the actinides do not follow the simple pattern found in the lanthanides.
  Immediately after La the 4f orbitals become appreciably lower in energy than the 5d orbitals. Thus in the lanthanides the electrons fill the 4f orbitals in a regular way (apart from minor differences where it is possible to attain a half filled shell). It might have been expected that after Ac the 5f orbitals would become lower in energy than the 6d orbitals. However, for the first
  four actinide elements Th, Pa, U and Np the difference in energy between 5f and 6d orbitals is small. Thus in these elements (and their ions) electrons may occupy the 5f or the 6d levels, or sometimes both. Later in the actinide series the 5f orbitals do become appreciably lower in energy. Thus from Pt
  onwards the 5f shell fills in a regular way, and the elements become very similar.

How do we know when the energy of the orbitals of a subshell become lower or higher than the orbitals of another subshell? Can this just be found experimentally or is there some theoretical explanation too?


texts: How do you Synthesise a Fatty Acid Amide?

texts:
How would you go about synthesising a fatty acid amide, preferably by means of a high-yield reaction. Please provide an explanation that I, as a grade 12 chemistry graduate, could understand.

I am familiar with:

Fatty acids
Carboxylic acid
Equilibrium reactions & constants
Amide groups
Amines
Alkanols
Esterification

If you need to use terms I may be unfamiliar with, it would be nice if you could explain them or provide a link to an explanation.


texts: Number of π electrons in all trans-2,4,6-octatrienoic acid

texts:
Sketch the Lewis structure of all trans-2,4,6-octatrienoic acid.
(a) Consider the delocalized π electrons. Employ the particle-in-a-box model. Drawing on your knowledge about the occupation of orbitals in atoms what is the highest occupied state? Sketch the occupation of the energy levels with electrons using ↑ and ↓.

I wondered if the electron lone pairs on the oxygen atoms also counted as π electrons since resonance structures exist where these lone pairs can be delocalised over the molecule.

If so, how would this correspond to using them to find the length of the conjugated system because wouldn’t that give extra length where there was no double bond?


texts: Under what circumstances is working in the chemistry lab hazardous to health in the long term?

texts:
I would like to know when working in the Chemistry lab would be hazardous to health in the long term. Because as everyone who worked in the chemistry lab knows that they would be handling many compounds that are harmful to human health. Many of those reagents for example especially organic ones are carcinogenic. While some are toxic to humans. Even with safety precaution, we would inevitably be exposed to those chemicals when working with them such as inhaling them. So actually I wonder whether it is safe to work in the chemistry lab especially with so many carcinogens. Im afraid of getting cancer due to this.
(I'm already halfway through my undergrad chemistry course.)


texts: Trends in solubility of group 2 nitrates

texts:
In my lab report, we are required to explain the trends in solubility of group 2 salts, going down the group. I had explained all of the trends except one, group 2 nitrates. The following is the data provided.

$\ce{Mg(NO3)2}$ – $\pu{0.49 mol}$ per $\pu{100 g}$ of water

$\ce{Ca(NO3)2}$ – $\pu{0.62 mol}$ per $\pu{100 g}$ of water

$\ce{Sr(NO3)2}$ – $\pu{0.16 mol}$ per $\pu{100 g}$ of water

$\ce{Ba(NO3)2}$ – $\pu{ 0.04 mol}$ per $\pu{100 g}$ of water

So as the data shown, the solubility first increases and then decreases. My speculation is that the general trend should decrease but $\ce{Ca(NO3)2}$ has some special properties which makes it more soluble or $\ce{Mg(NO3)2}$ has some special which makes it less soluble. I searched the internet and all I got is "All group 2 nitrates are soluble" with no explanation regarding the trend.

Please correct my speculations if they're wrong and also provide an explanation regarding this trend.


texts:
I need to calculate the molar mass and density of the shape memory alloy $\ce{Co49Ni21Ga30}$
(I suppose the numbers indicate the mass percentage).

To get the molar mass, is it correct to use the formula below?

Mol_mass_compound = Mol_mass_Co*0.49 + Mol_mass_Ni*0.21 + Mol_mass_Ga*0.30

Regarding the density, how do you suggest to proceed? Thanks!


texts: Enthalpy definitions. What are their main differences?

texts:
The definition of enthalpy is properly described in here.

The principal objective of this question is mainly academic. In order to any students with internet connection can find a definition and an example of the enthalpy concept applications.

What are the main differences of:

Standard enthalpy
Enthalpy of atomization
Enthalpy of formation
Enthalpy of hydration
Enthalpy of reaction
Enthalpy of combustion
Enthalpy of solution
Enthalpy of lattice dissociation
Enthalpy of lattice formation
Enthalpy of mixture
Enthalpy of excess mixture
Enthalpy of (any phase transition)
Law of Hess
Law of Kirchhoff

Any other definition not listed here


texts: Determining stoichiometry in ICP-OES data analysis

texts:
I have questions regarding data analysis for an inductively coupled plasma (ICP) experiment from a paper by Wang et al. [1].

The generic formula for the chemical compound is $\ce{Na_{2−x}Fe[Fe(CN)6]}$.

In the paper, it was mentioned that chemical formula and ICP data are

\begin{array}{lrr}
  \text{Formula} & \ce{Na} / \mathrm{ppm} & \ce{Fe} / \mathrm{ppm} \\\hline
  \ce{Na_{1.53}Fe[Fe(CN)6].{4.2}H2O} & 112300 & 357200 \\
  \ce{Na_{1.67}Fe[Fe(CN)6].{3.9}H2O} & 116100 & 339400 \\
  \ce{Na_{1.73}Fe[Fe(CN)6].{3.8}H2O} & 118400 & 332400 \\
  \ce{Na_{1.68}Fe[Fe(CN)6].{3.9}H2O} & 112000 & 332700 \\
\end{array}

My question is how they determined the $\ce{Na}$ number ($1.53$, $1.67$, and so on) on each cases based from the $\mathrm{ppm}$? I tried to make a $\mathrm{ppm}$ ratio of $1:2$ for $\ce{Na}$ and $\ce{Fe}$ however the number does not match with the paper.

Reference

Wang, W.; Gang, Y.; Hu, Z.; Yan, Z.; Li, W.; Li, Y.; Gu, Q.-F.; Wang, Z.; Chou, S.-L.; Liu, H.-K.; Dou, S.-X. Reversible Structural Evolution of Sodium-Rich Rhombohedral Prussian Blue for Sodium-Ion Batteries. Nature Communications 2020, 11 (1), 980. DOI: 10.1038/s41467-020-14444-4


texts: Why can't oxalate ion donate two pairs of electrons from the two double-bonded oxygen atoms

texts:
So, I read that an oxalate ion is a bidentate ligand but since I saw that it has 4 oxygen atoms I was confused as to why it isn't a tetradentate ligand instead.

I searched it on Google and found this:
Oxalate ion dentiticity - why is it bidentate and not tetradentate?

Now, in the link it's implied that the oxalate ion can donate the 2 pairs of electrons either from the 2 oxygen atoms having negative formal charge or from 1 "double-bonded" O atom and 1 negatively charged O atom.

But why can't the two pairs of electrons be donated from Both the "double-bonded" O atoms?
 Why isn't this "third" bonding mode possible?

EDIT:  From the comment below, I infer that because of resonance, there is no double-bonded or negatively charged O atom in the Oxalate ion; rather all of the O atoms have a partial negative formal charge and double-bond character, is that correct?

So, can electrons be donated from any O atom in the ion?

(And so did the answer in the provided link just ignore this for the sake of simplicity?)


texts: Why basicity decreases for leaving groups, but nucleophicity increases for an overall compound, going down the periodic table?

texts: Basically, I read that nucleophilicity increases going down the periodic table within a particular group, due to polarizability, but basicity decreases down a group (or family) in the periodic table, because those atoms can stabilize a negative charge, making them good leaving groups. Don't these two points seem to contradict each other, since increasing nucleophilicity should increase basicity?


texts: Chelation and its relation to transition metal ligands

texts: Can someone explain chelation and its relation to monodentate and tridentate ligands? I dont understand what they mean by chelate effect and chelating rings.


texts: When a truck comes into the shop with extreme ice that is rock hard, is there a way to remove it fast? Any tricks of the trade?


texts: Why do methane molecules have 15 degrees of freedom?

texts:
I've just been learning a little thermal chemistry including the equipartition theorem. As part of this, my textbook discusses how to figure out the degrees of freedom for different chemicals.

The answer to one of the exercises says methane has 15 degrees of freedom: 3 for translation, 3 for rotations and 9 for vibrations. I am confused by two of these.

Firstly the text says that diatomic molecules like oxygen gas only have 2 rotational degrees of freedom, because they can't rotate about their axis of symmetry. However methane has an axis of symmetry, so why does it have 3 rotational degrees?

Secondly I don't understand where all the vibration degrees of freedom come from. The molecule has 4 bonds, so wouldn't each bond have one degree for kinetic energy and one for potential energy, for a total of 8 degrees, not 9?


texts:
According to Médecins Sans Frontières propylene glycol can dissolve plastic:

  As propylene glycol can dissolve plastic... (Source).

Is this claim true? This seems rather spurious to me. If it matters, for a specific "plastic" I am particularly interested in evaluating the claim in regards to polypropylene and polyethylene as both are materials common for making syringes.


texts: Why does solubility of solids sometimes decrease with temperature increase?

texts:
Recently I was researching $\ce{Ca(OH)_2}$, and I found this on Wikipedia:

\begin{array}{|c|l|}\hline
{\rm \color{blue}{Solubility~in~water}}
 & {\mathrm{0.189\,g/100\,mL}\   (0\,^\circ\mathrm{C})} \\
 & {\mathrm{0.173\,g/100\,mL}\  (20\,^\circ\mathrm{C})} \\
 & {\mathrm{0.066\,g/100\,mL} \ (100\,^\circ\mathrm{C})} \\\hline
\end{array}

Can you explain why solubility decreases when temperature increases?


texts: Meaning of Partial Half-Life for Two Parallel Reactions

texts:
Consider two parallel reactions:
$$\ce{A   ->  B }\tag1$$
and
$$\ce{A ->  C}\tag2$$
What is the meaning of partial half life of the equation $(1)$ and that of equation $(2)$ with respect to above reactions?
It seems to me that it means the half life when one of these reactions are taking place individually, one-at-a-time, and not simultaneously. For example, partial half life of the equation $(1)$ is when half of $\ce{A}$ converts to only $\ce{B}$ and not to $\ce{C}$.


texts: Nomenclature of complex benzene-based substituents

texts: For a complex alkyl substituent, (at least the ones I have come into contact with thus far) you name it as a chain numbering from the first non-parent carbon and placing the name in square brackets: e.g. isopentyl can also be named [3-methylbutyl]. What is the convention for more complex benzene-based substituents? Specifically, can you still use the more common names like phenol and toluene as a parent for your name if say you bond C5 of 2,3-dimethylphenol to your parent and what suffix will you use?


texts:
HClO4= 100.5, d HClO4=1.8, (ACO)2O=102, d (ACO)2O=1.1, H2O=18, d H2O=1

A) Preparation of 100 ml perchloric acid 0.1 Molar aqueous solution. below is my answer, but what I'm not sure is that the density the problem has given is for 100% pure acid or 70%. below I calculated the density for 70% assuming 1.8 is for 100%.

d_70%=  100/(70 x 1/1.8+30 x 1/1)=1.452
M=10αd/MW=10x70x1.452/100.5=10.11 M

M_1 V_1= M_2 V_2→10.11 x V_1=0.1 x 100→ V_1≅1ml

B) Preparation of 100 ml perchloric acid 0.1 Molar non-aqueous solution in acetic acid. Okay about this one. So all I know is that I need to remove all water in the acid by adding acetic anhydride, and the ratio is 1/1:

I thought about how to calculate the volumes of both acid and acetic anhydride, and maybe I can use the density, or tried to create some equation, but none actually reached a final answer. So I tried this, I'm not sure this actually makes sense:

70/100 x 1/1.8=0.39 ml

M_pure=  ( 0.7/100.5 x1000)/0.39=17.86 M

M_1 V_1= M_2 V_2→17.86 V_1=0.1 x 100→V_(pure acid)=0.56ml

1-0.56=0.44 ml water

0.44ml x 1g/1ml x 1mol/18g x  (1 mol (ACO)_2 O)/(1 mol water)  x 102g/1mol x 1ml/1.1g=2.27ml acetic anhydrade

So 1 ml perchloric acid and 2.27 ml acetic anhydride, up to 100 with acetic acid


texts: How to synthesize large negative thermal expansion polymer driven DBCOD?

texts:
I am trying to learn about large negative thermal expansion of a polymer known as DBCOD. What I'm having trouble is finding out if a Chemical Vapor disposition chamber is used in the heating up of the DBCOD, or is there another form of heating is being used?
What is used to draw (fish) out a strand that alien the molecules the same way? Basically name of methods and equipment used to make a thin film of DBCOD.


texts: How to determine DDVP quality before appplication

texts: The question is quite straightforward I need to determine the quality of  2,2-dichlorovinyl dimethyl phosphate (commonly abbreviated as DDVP) it is solved in xylene (50%). The purpose is to know if it can kill the insects. The determination must be fast and an a person with few knowledge of chemistry must be capable of carry it out.


texts: Is methanol really more acidic than water?

texts:
The question Why is methanol more acidic than water? deals with the reasoning of why methanol is more acidic than water. However, as mentioned in the comments of that question, the acidity constant of water is $14.0$, as confirmed by two sources$^{[1][2]}$, with one of them offering a very convincing explanation. The Wikipedia page$^{[3]}$ for methanol quotes its acidity constant to be $15.5$.

So it would seem, water is more acidic than methanol. But an answer to the question mentioned above gives a good reasoning for why methanol is more acidic than water (it doesn't deal with the pKa of water, though). Also, the answer mentions that water would be much worse an acid in DMSO. Another question implies that methanol and other alcohols are more acidic than water.

On the other hand, it is also true that we regard alkoxide ions as being more strongly basic than the hydroxide ion (thus we use them primarily for elimination reactions).

This leaves us in a fix. So what is the ultimate truth?

    [1]: What is pKa of water? - Chemistry ChemLibreTexts
    [2]: Water (Data Page)
    [3]: Methanol


texts: Why does the plot of volume and temperature have a kink in a second order phase transition?

texts:
The $(b)$ part of the figure shows how thermodynamic variables change in a second order phase transformation.
We observe there is a kink in the plot of volume with temperature.
Why is that so?
The plot is from http://faculty.chem.queensu.ca/people/faculty/mombourquette/Chem221/5_PhaseChanges/PhaseThermo.asp


texts: How can nitrogen achieve +5 oxidation state?

texts: Nitrogen has no available d-orbitals. Yet, it forms compounds where its oxidation state is +5, like in nitric acid. How?


texts: Whose concentration is more 1 molar or 1 molal?

texts:
I was reading about concentration terms like molarity, molality, etc. and then I came across a question: which concentration is more:

1M(molar) of solute x dissolved in water vs.
1m(molal) of solute x dissolved in water

When I Google it, I did not find exact answers but did find some related information.
My approach is:

Convert 1M into molality and then compare if it is less or more than 1m. (?)
The density of water is 1kg per L.
When solute is added to it, density would definitely increase(?)
And therefore 1L of that solution will weigh more than 1 kg.
now if we calculate molality of 1M solution it would be less than 1m . (?)
am I correct ??
Density would always(?) Increase after adding solute
**Hence 1m will always be more than 1M **


texts: Best reagent to convert 4-chloro-4H-pyran into an aromatic compound

texts:
My question:

My attempt: (I am not really good at mechanisms, so a little help would be good. Thank-you)

I do not know what kind of reactions these will give.


texts: Why does the composition of Ocean Water list sodium and chloride separately?

texts:
This is the site I am using.

It is also found here, but this uses mg/L instead of percents.

It lists Sodium at 30.8%, and Chloride at 55.3%. How can this be? Shouldn't the two be listed as Sodium Chloride or salt? Because as far as I know, there is no way to obtain chloride on its own.


texts: Calculating the enthalpy of polymerisation of ethylene given the bond strengths

texts:
Given the average bond dissociation enthalpies of a $\ce{C-C}$ bond (say $x$) and a $\ce{C=C}$ bond (say $y$), find the enthalpy of the following polymerisation reaction (per mole of ethylene):
$$\ce{nCH_2=CH_2 -> [-CH2-CH2 -]_n}$$
where $n$ is a large integer and $x, y$ are in $\pu{kJ/mol}$.

According to me, this should simply be $y-x$ as for every double bond broken, a single bond is formed. But the source book of this problem states the answer to be $y-2x$ claiming that for every double bond broken, 2 single bonds are formed.
How is this possible?


texts: I have access to a GC/MS, FID, and a spectrophotometer. My first thought was to derivatize with trimethylsilylating agent, then run it by GC. Unfortunately the water is problematic. Heating it is likely to destroy the ascorbic. I don't have access to a manifold freeze-drier. I do have access to a rotovap, but I don't think that works well for removing water. I do have access to a freezer, but no way to vacuum the sample down to 0.006 atmospheres. Titration is out of the question because I don't have a clue what else is in the sample.


texts: Enantiomerically pure ketone reaction under acidic conditions gives 1:1 mixture of diastereoisomers?

texts:
My problem is such:

My thinking is that perhaps the explanation has something to do with the carbonyl group being prochiral and having two faces, each side generating one of two diastereoisomers? I'm not sure...


texts: Why is a set of p-functions added to the minimum basis sets of Li and Be?

texts: The minimum basis set consists of the smallest number of functions necessary to contain the electrons of the neutral system. In the book Introduction to Computational Chemistry, Second Edition, by Frank Jensen, it is stated that "a set of p-functions" usually is added to the minimum basis sets of Li and Be atoms, despite them containing 3 and 4 electrons respectively and thus would require 2 s-functions. I can not, however, understand why.


texts:
The process of creating 2D depictions is explained in detail here. This way, it is possible to create a 2D image via running e.g.

obabel  -O 2d_depiction.png

However, how do I generate a ball and stick 3d depiction (as image) instead?


texts: Organic molecules with fast non-radiative decay rates

texts: What structural features in an organic molecule would promote fast non-radiative decay to a ground state, for instance in an aromatic π-conjugated system ?


texts: Does the ignition temperature of a substance decrease with the concentration of oxygen?

texts: Is it possible for a substance to undergo combustion at a temperature lower than its ignition point if the concentration of oxygen increases?


texts: How to determine the most reactive hydroxyl group of α-ᴅ-glucopyranose?

texts:
In the following reaction, only one of the hydroxyl groups in D reacts under the given conditions:

I was wondering which OH group reacts and why? Also I have been trying to determine the structure of E based on which hydroxyl group reacts.
My thoughts are that OH in the side group can react via SN2 with the reactants, but the OH right adjacent to the ether O can react leaving a carbocation that can be stabilised by lone pair from O. This would mean SN1 and a completely different product.
Can someone please explain the correct mechanism?


texts: Before going into stable states ( i.e less energy states ) , do exothermic systems become unstable for a short time on the basis of Kinetic Energy?

texts:
In most of the cases the reactions are exothermic because all systems want to reduce their net energy and one way to do that is by loosing the $KE$ of the molecules to the surrounding molecules by collisions.

Now suppose that that the molecules of our system cannot emit any radiation so the only way for them to reduce their net energy is by giving their $KE$ to other molecules which are not a part of the system.

Now if I make water with Hydrogen and Oxygen, it results in an exothermic reaction. My question is that hasn’t the $KE$ of the molecules increased when we have mixed Hydrogen and Oxygen together before they pass their $KE’s$ to the molecules of the air? Or in other words does every exothermic system becomes unstable ( because of the increase in the $KE$ of the molecules and hence in net increase in energy ) before it can pass out it’s energy to the surroundings ? And is it that exothermic systems will tend to increase their energy if they cannot pass on their energy to the surroundings ?


texts: How stable is Remdesivir when vial vacuum is broken and/or it is reconstituted with sterile water?

texts:
I was recently looking at how long can Remdesivir be stored in its different forms.
I came up across several articles provided by the FDA and Gilead Sciences and others.
What caught my eye was the fact that after you reconstitute Remdesivir with sterile water you cannot store it at all! The manual and articles provided by numerous sources all say the same thing. they clearly state that you should use the reconstituted solution right away, meaning combine it with a NaCl serum. The serum then can be stored for up to 48 hours inside the fridge (no more than that). As stated by the FDA article and also another article by the EU medicines agency this is mainly because of bacterial and parasitical contamination, which is irrelevant to this question.

Care should be taken during admixture to prevent inadvertent microbial contamination. As there is no preservative or bacteriostatic agent present in this product, an aseptic technique must be used in the preparation of the final parenteral solution. It is always recommended to administer intravenous medication immediately after preparation when possible.
-- FDA

Chemical and physical in-use stability has been demonstrated for 24 hours at 25°C. From a
microbiological point of view, unless the method of opening/reconstitution/dilution precludes the risk of
microbial contamination, the product should be used immediately. If not used immediately, in-use
storage tomes and conditions are the responsibility of the user.
-- European Medicines Agency

So my question is putting aside the problem of keeping the product aseptic, How long does the Remdesivir molecule itself manage to be stable inside a vial reconstituted with sterile water. (Note that the vial vacuum has also been broken)
It would also be helpful to describe the chemical processes/reactions that happen, causing the product to lose its efficacy.


texts: What is the characterstics of additives that it must posses to make any mixture hypergolic?

texts: This is about hypergolicity of rocket propellant.Turpentine gave hard-start with RFNA and WFNA but excellent with mixed acid(mixture of HNO3 & H2SO4).Similarly,Furfuryl alcohol & WFNA(also RFNA) become hypergolic mixture.So,what properties must additives posses to ignite particular mixture at any time without requiring oxygen?


texts: Is there an experimental way of measuring the critical concentration of pigment in paint?

texts:
With an assigned, generally paint-based, experimental project I've been looking up CPVC or critical pigment volume concentration in binders. CPVC defines the point of addition of pigments after which follows a severe drop in blistering and increase in rusting on the applied surface due to the pigment not while binding with the binder having voids in it. But going past the critical point can also make the paint fragment and crumble or maybe even lose just some of its pigment, in conclusion lose efficiency.
Paint manufacturers use this to make paints a certain type by knowing the CPVC of the mixture with which they can adjust to make the fitting paint for the job but the way they know is by applying the general formula for determining the point which is

$$CPVC = \frac{1}{ 1 + OA * ρ / K }$$

With the 'ρ' standing for the specific gravity of the pigment, 'K' specific gravity of the binder and 'OA' which is the oil absorbent number of the pigment depended of the exact pigment and the binder. But excluding it is there a way that a clear mixture of paint without any additions like extenders for example and just acrylic polymer binder and an inorganic pigment type can be used to calculate the near CPVC of it. Can it maybe be done by centrifuging a dry paint sample in a centrifuge tube and later sampling the super natant that will contain an ammount of pigment and binder that would dissolve in it  and fall apart from the rest of the paint and quantitatively analysing it in a high performance liquid chromatograher? By increasing temperature or the pH it could also affect the stability (the CPVC) so can that method be used effectevly? Is there a better one and not by just assuming the CPVC by observing the paint on a wall?
Any help could be really helpful sense im young and do not know the process well, only by researching the concept itself, and it's hard to find details and think of a valid project idea.


texts: Would Al ions still be reducd to Al metal if it was aqueous soltion?

texts:
To my knowledge, Aluminium is mostly mined in the form of Aluminium oxide or Al2O3 and then the Bayer process is used to extract and refine the pure Aluminium.

Now, The Al2O3 must be in a molten state when the process occurs. Why is that? Why must it be molten?

Also, Would the Al(3+) ions still be reduced to the Al metal if it was in an aqueous solution instead of being molten?

Thanks,


texts:
I have purchased an "unknown" white coloured powder from the market which can frost glass objects. Here are some properties of this powder

White in colour
When mixed with HCL or water, it results in the soluion becoming ice cold, the reaction is endothermic.
When kept for a while (10 minutes) the white powder settles at the bottom of the plastic vessel and the acid floats above it.
When stirred, the entire solution becomes milky
When glass is dipped in this solution for 90 seconds, it becomes frosted/translucent.

Since I am not sure what this chemical is, I cannot determine the safest method to dispose it. The person from whom I brought this told me to put it down the drain, but I wouldnt choose to do that before I know if it will not effect the water table near my locality.

Can someone point out what could this powder be, and the best way to dispose it off?


texts: How does the relationship between carbonate, pH, and dissolved carbon dioxide work in water?

texts:
Fish keepers use a table like the one below to determine dissolved $\ce{CO2}$ by observing the color of a pH indicator in water with a known concentration carbonate solution (typically 4 degrees KH ~= 70ppm carbonate).
I'm curious where the equation in the top of the picture comes from though.  Below is my reasoning for wondering where that equation comes from and knowing would (I think) answer all my questions below too.
It appears to me that the equation doesn't work with pure water (water lacking carbonate).
I can think of a few reasons for this:

The equation implies that either pure water cannot hold any $\ce{CO2}$
$\ce{CO2}$ concentration and carbonate concentration are not truly independent
Depending on how the algebra was done, it could be that pH isn't well defined without the presence of carbonate.
It's an approximation that doesn't work everywhere.

My gut says its #4 or #2 but then the table would be kind of worthless unless $\ce{CO2}$'s contribution to carbonate is low relative to the amount added to solution.  If this is the case, I wonder where does the table become inaccurate.


texts:
In my chemistry textbook, the chapter "Structure of Atom" deals with the old Bohr's model and the new Quantum mechanical model. But when I read the contents of the new model of atom, there were terms like energy levels, shells being repeated. I failed to understand the context. Moreover, Bohr's model has been discarded so why do we still talk about energy levels/ orbits in an atom?

Basically, I want a satisfactory explanation of these terms: energy levels, orbits, sub orbits, shells, sub-shells, orbitals and principal quantum number in accordance with the Quantum mechanical model of the atom.

I tried to understand this from two other books but there too the distinction was vague.

I also read the contents of:

Is there a difference between energy levels and electron shells?

https://www.khanacademy.org/science/chemistry/electronic-structure-of-atoms#orbitals-and-electrons

PS: Please provide an answer keeping in mind that the questioner is a Grade 11 student.


texts:
I'm working on a pet project and I'll need some helium. I was wondering if there were any reactions that I could perform at home to produce helium cheaper than it would be to buy helium from someone else.

Anyone know of such reaction off the top of their head?


texts:
Where can I get the latest rules on IUPAC nomenclature of coordination complexes?
I have J D Lee book which is also assumed to  have outdated rules.


texts: Is dialkyldimethylammonium chloride suitable for sterilization in mycology?

texts:
In hobby-mycology 70% rubbing alcohol is commonly used for sterilizing work surfaces, bags, syringes, still air boxes, basically everything.

Alcohol however, seems to have some downsides, when it comes to mycology as it needs a long soak time to actually kill anything and it doesn't kill mold and mold spores at all, which is one of the most common contaminants.

So I am looking for something, which does not create toxic fumes, does kill bacteria and fungi spores including mold and acts quickly.

Is dialkyldimethylammonium chloride the right solution for me? If yes, what dilution should I use? Would 2% be sufficient? Does it become denatured after 24h mixed with water like bleach? And most importantly, is it safe for use at home? Will it cause residue buildup, like bleach would?


texts: Misunderstanding about the spin part of the Jahn Teller effect

texts:
In the paper Stability if Polyatomic Molecules in Degenerate Electronic States II - Spin Degeneracy the author wrote:

  Thus a twofold degeneracy cannot produce instability for a molecule containing an odd number of electrons with spin.

It is really disturbing for me as I'm looking to the Jahn-Teller effect being strong on the $e_g$ orbitals when there is a odd number of electrons on it.


texts:
I took the kids to the Science Museum in Canberra (Questacon) and one of the toys we brought back was a Home-Made High Bouncing Ball.

Now I did it with the kids and it was amazing. You pour the powder in the mould, hold it underwater for a minute. Dry it in the mould for two minutes and open the mould and let it dry.

The end result was like the high-bouncer balls we used to play with as kids. (Lots of fun).

My question is: What is the chemical reaction in a home-made high-bouncer ball? (I'd also love a picture I can show my kids - but that is not essential).


texts: Why is quinoline less basic than pyridine?

texts: Quinoline is less basic than pyridine, even though it has more resonating structures. Why? Does the negative inductive effect reduce basicity of quinoline?


texts: Condenser shooting out hexane in a soxhlet extraction

texts: Im running a soxhlet extraction using hexane as the solvent. Once the hexane has filled up the soxhlet, a considerable amount of hexane will come out on top of the condenser. Is this an issue with pressure or defects in the glasses?


texts: Can we prevent metal corrosion by creating a vacuum around it?

texts: I have a device in a box which has parts of metal. So can I prevent corrosion by creating a vacuum around the metallic object?


texts: Why does radioactive matter decay in series of half-lives?

texts:
I was studying types of nuclear decay, and I came across the concept of "half-life". And I started wondering why does nuclear matter decay in half-lives? In other words, why does the rate of nuclear decay decrease as a function of time?

Is it because as more atoms decay, the surface area of the radioactive matter decreases, and the number of atoms "exposed" decrease? Does the outer layer of atoms somehow "shield" the inner atoms and stabilize them, preventing them from decay?

Or is there another mechanism at play?


texts:
Cu has an anomalous electron configuration. $\ce{Cu ~=~ 1s^2~2s^2~2p^6~3s^2~3p^6~4s^1~3d^{10}}$, it does not follow the usual pattern. In this case, the 3d subshell is filled before the 4s, which usually happens in the reverse order ($\ce{1s^2~2s^2~2p^6~3s^2~3p^6~4s^2~3d^{9}})$.

My question is, can you tell by an element's position on the periodic table (Group #, Row #, Block, etc.) that it will have an anomalous electron configuration? Do I have to memorize which elements have this property?

I am noting that Cu is in the 1B Group of Transition metals which implies that it has one valence electron, this is consistent with its configuration. will this be true for all cases?

Also: $\ce{Fe ~=~ 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6}$ and is a transition metal as well (Group 8). This implies it must have 8 valence electrons. But following the definition of valence electrons (The number of electrons in outermost shell), $n = 4$ is the outermost shell and I get a conundrum. Obviously if I add $\ce{4s + 3d}$ electrons everything is good. Why is this?


texts: Decrease in temperature of an aqueous salt solution decreases conductivity

texts:
Why does the conductivity of a water solution drop as the temperature decreases?

How are these two related?


texts: Is this the correct mechanism of the formation of the nitronium (NO2+) ion from sodium nitrate and sulfuric acid?

texts:
I am currently working on a mechanism for forming paracetamol (or N-(4-hydroxyphenyl)-ethanamide). The typical reaction to nitrate the phenol (starting product) is $\ce{NaNo3}$ with a catalyst of sulfuric acid. The sulfuric acid is required as a catalyst to form the nitronium cation - an electrophile - to attack the aromatic phenol. Unlike the nitration of toluene (for TNT) or benzene, it is possible to use $\ce{NaNO3}$ because the oxygen in the hydroxy group is activating.

My proposed mechanism for the formation of the nitronium is this:
$$\ce{NaNO3 + H2SO4 + 2H2O <=> Na+ +NO3- + SO4- + 2H3O+}$$
I think this is a likely equilibrium between the starting ions. Sulfuric acid is a strong acid, and therefore to use a mechanism with it undissociated I think unlikely - the reaction would be slower, due to lower concentrations of the undissociated sulfuric acid. I know that $\ce{NaNO3}$ is fairly soluble, so would dissociate into ions.

I suggest attack of the $\ce{NO3-}$ by $\ce{H3O+}$, protonating one of the oxygens:
$$\ce{NO3- + H3O+ -> HNO3 + H2O}$$
$\ce{HNO3}$ has a Ka of ${24 * 10}$ - 24 moles of $\ce{HNO3-}$ present for every $\ce{NO3}$ we can attribute this to the stability of the $\ce{NO3-}$ ion, but it also is fairly low compared to the Ka of sulfuric acid - ${1*10^3}$. By adding sulfuric acid, a strong acid, it increases the concentration of $\ce{H3O+}$, therefore shifting the equilibrium to the right. This favors the reaction.

In the $\ce{HNO3}$ molecule the oxygen-hydrogen bonds are all different lengths - $\ce{N-O}$ is 119.9pm, or 121.1pm, and the $\ce{N-O-H}$ bond is 140.6pm. The $\ce{N-O-H}$ bond is clearly weaker than the other two bonds. This is attributed to the resonance effect - a valence electron from each oxygen interacts with a lone pair on nitrogen favorably, shortening and strengthening the bonds. Protonating the oxygen in $\ce{NO3-}$ thus weakens the bond. Protonating the oxygen a second time:
$$\ce{HNO3 + H3O+ <=> NO2+ + H2O + H2O}$$
Would probably break that bond.

The hydronium protonates the oxygen already protonated - resulting in an unstable intermediate. The positive charge pulls electron density from the $\ce{N-O}$ sigma bond onto the oxygen (inductive effect). This breaks the bond, and stabilizes the positive charge on the oxygen, and it becomes $\ce{H2O}$

However, the hydronium may protonate one of the other two oxygens. Why is the one already protonated more basic? The other two oxygens have a higher electron density, so would be more nucleophilic - better for the electrophilic $\ce{H3O+}$ to attack. A fraction would surely react in the way I have described, but I would think a much higher proportion would react on other oxygens.

Is this mechanism likely/correct? Could you explain how the second protonation occurs?


texts: Proving a relation for fugacity of component i in term of independent variables (T,V)

texts:
In Molecular Thermodynamics of fluid phase equilibria by Prausnitz et al. [1] the authors recommend to use the following equation which gives the fugacity of component $i$ in terms of independent variables $V$ (volume) and $T$ (temperature):

$$RT\ln\phi_i = \int_v^\infty\left(\left(\frac{\partial p}{\partial n_i}\right)_{T, V, n_i} - \frac{RT}{V}\right)\mathrm{d}V - RT\ln z$$

I know that I should use chemical potential definition to prove this equation, but there are many different ways to calculate it like using Helmholtz free energy or Gibbs free energy.

I would appreciate someone give me an idea or any references to help me proving this equation.

References

Prausnitz, J. M.; Lichtenthaler, R. N.; Azevedo, E. G. de. Molecular Thermodynamics of Fluid-Phase Equilibria, 3rd edition; Prentice Hall: Upper Saddle River, N.J, 1998. ISBN 978-0-13-977745-5.


texts: Theoretical Concentration (in PPM) of CO2 production after 1 minute

texts:
I recently conducted an experiment to determine ideal ratio of baking soda and citric acid that would produce the most amount of CO2 in water. We used 250ml flasks filled with 120ml water. The samples themselves all weighed a total of 6.5 grams contained various ratios of Sodium bicarbonate and Citric Acid.

The mixtures were dropped in the water, and stoppered with a CO2 meter which measured the production over a minute. We recorded the PPM of CO2 in the container after a minute for each sample. Overall, the rank of the results supported the hypthesis. However, I am having trouble determining the theoretical value to determine the accuracy.

For example, a 50:50 ratio of 3.25g Sodium Bicarbonate and 3.25g citric acid was recorded to have 102,946 PPM of CO2 in the container after 1 minute. How should I go about calculating the theoretical PPM of CO2 after a minute?

To recap:

250mL container
120mL water in the container
Mixture Dropped in water
Stoppered with CO2 meter, which measures PPM of CO2 in the air inside
the container
PPM recorded after 1 minute

How can I determine the theoretical value?

Any help or guidance will be greatly appreciated.


texts: How to visualize the rearrangement of a pentacyclic triterpene alcohol?

texts:
I was looking into the exam paper of last year when I found this:

Propose arrow-pushing mechanism for the reaction below.

I suppose it's a Wagner–Meerwein rearrangement. (Sorry for the dirty mechanism graph.)

Is the answer correct? How would I explain the stereochemical configuration of the reaction? And why doesn't the elimination (the leaving of proton) happen at carbon A, as the cation intermediate is just as stable as the others?
I tried drawing chair conformation graph of the reaction. I marked the possibly important groups in red for convenience.


texts: Enthalpy (H) formula: what is the pressure volume product

texts:
$$H=U+pV$$

Above is the formula for enthalpy or the sum of the internal energy and pressure volume product.

$-p\Delta V$ is work done by or on the system. But $pV$, yet very similar to work, I think, calculates the whole “cylinder”. Instead of just calculating the height difference of the cylinder before and after the air is condensed, it calculate the height of whole cylinder.

But anyway this is just my guess, what is it really?


texts: How long must a sample be irradiated before all 59-Co atoms are converted to 60-Co?

texts: For the interaction,  n$^0$ + $^{59}$Co $\to$ $^{60}$Co


texts: Isolating salt from sea water using filters

texts: Could a filter be used to isolate salt from sea water? Could we say that the water molecules are smaller than the molecules of salt dissolved in the water. I have no relation to chemistry or physics, so pardon the question if it's too naive.


texts:
Boyle's Law states that pressure is inversely proportional to volume.
However, let's take an example of a balloon: as we fill air in it, its pressure increases, but its volume also increases. Can anyone explain?

(source: ucdavis.edu)


texts: Ratio of energy required for electrolysis vs creating water

texts:
I had an idea a while back for a machine that would be totally green. Powered by a Hydrogen Fuel Cell. A big question came up: Where do I get the Hydrogen? I assumed that I could just electrolysis of water to create Oxygen (which would be released into the air) and Hydrogen (which would be used in the cell). But, then I remembered a key factor of bonds: Creating a bond gives the nuclei a more stable configuration, which releases energy. Breaking a bond requires an input of energy.

Let's say I use electrolysis to split water. This will take energy. Then I use a Hydrogen Fuel Cell to generate electricity. This process gives me the same amount of water that I just split.

Q: Which process uses/gives more energy? Would the above example result in a net gain or loss?


texts: Conductometric titration of Strong Acid And Strong base

texts:
Consider conductometric titration of Strong Acid with strong base say HCl + NaOH.

My question is why initially the conductance decreases. If H+ of HCl is consumed by OH- of NaOH, forming water and hence conductance decreases.  I agree to these.
But On other hand NaCl is also forming in same amount which can give rise to Conductance. So in my point of view Conductance must remain same or differ slightly. Instead of decreases considerably.


texts:
I need a solution of CuCl in HCl.  Since CuCl reagent is such a pain to source and work with (because it oxidizes so quickly) I was thinking that I could create the solution simply via electrolysis of copper electrodes in HCl.

Is anyone aware of research on this electrolytic reaction?  I don't have time right now to look for side reactions or to play with parameters (solution strength, voltage, etc.).

(Unfortunately I can't find any research specific to this, because CuCl-HCl electrolysis is a popular method of generating hydrogen, so all searches return papers on that.)


texts: Coordination number of chromium(III) oxalate complex

texts:
The coordination number refers to the number of binders that interact with the central metal ion. So, in the complex $\ce{[Cr(C2O4)3]^3-}$ chromium is bound to three oxalate ions.

Why its coordination number is considered 6? So, is it an incorrect definition of coordination number?

Can you help me?


texts: How to bond polymer to polymer (TPU on PMMA)

texts: I wanted to bond TPU films to PMMA slab. I  have tried thermal bonding but it is was not practical(I do not know why?). Can anyone please give me a method to bound them? Thanks


texts: Enolate formation and tosylate displacement in cis/trans decalin

texts:
What will happen in the following reactions? This is Problem 3d from Chapter 6 of Zweifel and Nantz's Modern Organic Synthesis.

I thought that after the hydroxyl group is converted into a good leaving group ($\ce{OTs}$), an enolate would be formed which would attack $\ce{CH_2OTs}$, but I guess the fused cyclobutane thus obtained would be too strained. What else could happen?


texts: Freezing point depression and organic molecules

texts:
Do organic molecules reduce the freezing point of water in the same way that inorganic salts do?  I've recently been swimming in lakes with a high organic content (e.g. mostly tannins.  There's a lake in this area called Tea Lake).  I've got an infra-red thermometer and readings taken from the water at this time of year before total freeze up have been around -1 to -2 degrees C.  Are these reasonable (accepting of course possible inaccuracies and calibration issues with the thermometer)?
Thanks,
Phil


texts: Cahn-Ingold Prelog rules concerning tie breaking on second level

texts:
comparing the cahn-ingold prelog priority of the above groups, I should first compare the atoms attached to the first carbon.
So we get:
(A): {O,C,H}
(B): {O,C,H}
(C): {O,C,H}
(D): {O,C,H}
therefore we have to consider the second level, and this is where I get confused:
Do I compare it this way:
(A):{C,H,H,H}
(B):{O,H,H,H}
(C):{F,C,H,H}
(D):{C,H,H,H}
I did this by rearranging all the "second level atoms" in descending order of atomic numbers.
since A and D are still in a tie, I rearrange all the "third level atoms" in descending order of atomic numbers:
(A):{H,H,H}
(D):{F,H,H}
so the priority is C>B>D>A
Is that correct?


texts:
From Googlebooks First Outlines of a Dictionary of Solubilities of Chemical Substances  By Frank Humphreys Storer:

  I find that lead tartrate is dissolved by tartrate of ammonia.

What is the final product?


texts: What is the chemical equation for cooking rice?

texts: What is the balanced chemical equation for the chemical reaction of cooking rice (including the formula for starch etc.)?


texts: How to differentiate hydrous and anhydrous compound?

texts: For an experiment, my teacher gave me containers of hydrates and their corresponding anhydrous compounds, but I have a feeling that for one of the compounds she switched the hydrate and anhydrous label by accident. How can I check if this is true?


texts: What is the activation energy of iron rust?

texts: Iron rusts to Geothite (FeO(OH)). What is the activation energy for this reaction? Where can I find this information?


texts: What are the chemical reactions and/or chemical processes that take place during SFE(supercritical fluid extraction)? Namely supercritical $\ce{CO2}$.


texts: Does adding slices of lemons to water reduce its chlorine content?

texts:
Often restaurants add slices of lemon to water. They seem to make the water taste better and perhaps reduce or at least cover up the chlorine taste.

I've heard that Vitamin C tablets can be used to remove chlorine from tap water.

Q: Does anyone know if lemons, being rich in vit C, will encourage the removal of chlorine from tap water?


texts: Which organic compounds have the most strongly negative enthalpies of formation?

texts:
I've been using the NIST Webbook to list organic compounds and look at their heats of formation (kJ/g, not mol). If I limit myself to three carbons, I still get over 400 results.

I can use some heuristics to guess which ones have strong heats of formation. I'm interested in kJ/g rather than /mol so smaller molecules are more likely, and certain bonds like $\ce{C=O}$ help, but that's not good enough for my project because I need to be certain.

Oxamic acid, ammonium formate, and ammonium acetate are up there, but who knows how many I might be missing, limited as I am to looking up small molecules?

So I'm hoping someone with a lot of experience might tell me something off the top of their head.


texts: Can cis-trans isomers interconvert via tunneling ?


texts:
Quoting from my textbook:

  Although stabilized by resonance compared with other carbocations, its resonance energy is much less than that of the starting benzene ring.

Here is more context :

Isn't that good? Isn't it more stable if it had less energy? Shouldn't it stay that way?

I feel like I'm missing something very obvious but I can't pinpoint it.


texts: Can the size of molecule oxygen reduce smaller? If yes, how is that possible? Is it related to proton and electron surrounding the nucleus?


texts: What results from the reaction of 4-phenylbutanoyl chloride in presence of AlCl3?

texts:
Please note that this is 4-phenylbutanoyl chloride:

My guess was that another molecule of 4-phenylbutanoyl chloride would react with the phenyl, thus forming a structure like the one below:

But this molecule seems somewhat awkward, and I am unable to name it. Is my guess correct? If yes, what would be its name?


texts: Partial Coverage During Zinc Plating Bath

texts:
I am experiencing partial coverage of a part during a DIY home zinc plating operation and was hoping someone here may be able to identify the cause of this.

I am using a solution of household vinegar and epsom salt to zinc plate some pieces during a motorcycle restoration but I am having difficulty getting the zinc to deposit on an area of a specific part.

On accompanying picture of a footpeg mount it is evident where the plating has not adhered.

I have done multiple runs and cleaned the part thoroughly between each run and even oriented it in different directions to the zinc anode and even connected my cathode connection point directly to the area not accepting any zinc all to no avail and was wondering if anyone has any ideas on what may be happening here and how I may resolve the issue. (My guess is there is an electrical or magnet field being generated by the "sides" of the part and preventing plating in this area as all other areas not visible have zinc adhered from the first run)


texts: Gibbs free energy and electrical potential

texts:
The relation between the Gibbs free energy and the electrical potential is:
$$\Delta G=-zFE$$
$z$ is the valence of the electrochemical reaction and $F$ is the Faraday constant.

If at equilibrium the $\Delta G$ is zero this means that also $E$ is zero but this is not true because $E$ at equilibrium is the equilibrium potential of the electrochemical reaction considered.

This makes some confusion in my mind and for sure I'm not properly consider something.
Can someone help to clarify my mind?


texts: What benefits do higher-rated NMR tubes provide?

texts:
You can buy NMR tubes in a huge variety of qualities, with an equally huge difference in price between the cheapest and the most expensive NMR tubes. They are usually rated for a specific spectrometer frequency, e.g. 300 MHz+ or 600 MHz+.

What is the difference between these different grades of NMR tubes? And how large is the effect on the quality of the spectra if a lower-grade tube is used?


texts:
Could you tell me the name of this glassware? I found it in the laboratory with a label that says "container of stoichiometry", but I have not found more information about it, especially about the uses that it could give.

Thank you!


texts:
Why don't all the atoms in s-cis-1,3-butadiene lie in one plane?

All carbon atoms are $\mathrm{sp^2}$ hybridised and I feel that there would be no $\ce{C-C}$ bond rotation due to the conjugation that leads to a double bond on $\ce{C2-C3}$ making them all lie on a plane.

Is it any different for s-trans-1,3-butadiene?


texts: I am trying to convert $\ce{KCl}$ to $\ce{KClO3}$ through an efficient process.  I realize that I could electrolyze a solution of $\ce{KCl}$ to obtain some $\ce{KClO3}$ as a precipitate, however this seems inefficient as some chlorine will inevitably escape as a gas. Could an oxidizer such as hydrogen peroxide or sulfuric acid achieve this?  I realize that $\ce{Cl-}$ would be oxidized to $\ce{Cl}$ but I thought that there may be a way around that.  What is the best method?


texts: In dS≥dQ/T, material equilibrium means that there is not material changes at all or that a material change can be reversible and at equilibrium?

texts:
I am reading Levine's Physical Chemistry, I know how to arrive to that equation, but I have questions.

First, $\mathrm{d}S=\mathrm{d}Q/T$ for material equilibrium, but if there is a heat flow I understand that there is a reversible process going on, what kind of process can it be? Only a reversible thermal or mechanical process or also a reversible material change?

Second, the book says

$$\mathrm{d}S > \frac{\mathrm{d}Q_\mathrm{irrev}}{T} \qquad\text{and}\qquad \mathrm{d}S = \frac{\mathrm{d}Q_\mathrm{rev}}{T}.$$

Then states the equation $\mathrm{d}S ≥ \mathrm{d}Q/T$ and says $\mathrm{d}S$ equals $\mathrm{d}Q/T$ for a reversible process and $\mathrm{d}S$ is greater than $\mathrm{d}Q/T$ for an irreversible chemical reaction or phase change.

I imagine that the heat flow is different if the process is reversible or irreversible and that the equation $\mathrm{d}S≥\mathrm{d}Q/T$ takes into account that the $\mathrm{d}Q$ is different, is this correct? I think I am a little confused just because there are no more subscripts in $\mathrm{d}S≥\mathrm{d}Q/T$.

Also, I think that the heat flow due to a irreversible process is greater than the heat flow due to a reversible process that goes to the same states, why is that?


texts: How does precipitate affect cell potential?

texts:
A cell is set up with copper and lead electrodes in contact with $\ce{CuSO4(aq)}$ and $\ce{Pb(NO3)2(aq)},$ respectively, at $\pu{25 °C}.$ The standard reduction potentials are:
$$
\begin{align}
\ce{Pb^2+ + 2 e- &-> Pb} &\quad E^\circ &= \pu{-0.13 V} \\
\ce{Cu^2+ + 2 e- &-> Cu} &\quad E^\circ &= \pu{+0.34 V}
\end{align}
$$
If sulfuric acid is added to the $\ce{Pb(NO3)2}$ solution, forming a precipitate of $\ce{PbSO4},$ what will happen to the cell potential?

I know the lead is the anode while the copper is the cathode:
$$\ce{Pb(s) + Cu^2+ -> Pb^2+ + Cu(s)}$$
The addition of $\ce{H2SO4}$ will cause less $\ce{Pb^2+}$ to be in the solution, thus causing the equilibrium to push to the right creating more $\ce{Pb^2+}.$ With more $\ce{Pb^2+},$ if you were to put it in the Nernst equation, would the greater number in the log expression cause the cell potential to decrease?


texts: If PQ, T2U2, RS2 and VW4 have the same Ksp, which has the lowest solubility in moles of solute per litre?

texts:
If the solubility products of the following ionic compounds all have the same numerical value, and all solubilities have values between zero and one, which one would have the lowest solubility in moles of solute per litre?

$\ce{PQ}$

$\ce{RS2}$

$\ce{T2U2}$

$\ce{VW_4}$

Their chemical equations and $\ce{Ksp}$ values would be:

$\ce{PQ <-> P +Q}$  and $\ce{Ksp=[P][Q]=[P][P]=[P]^2}$
$\ce{RS2  <-> R +2S}$ and  $\ce{Ksp=[R][2S]^2=[R][2R]^2=4[R]^3}$
$\ce{T2U2  <-> 2T +2U}$ and $\ce{Ksp=[2T]^2[2U]^2=[2T]^2[2T]^2=16[T]^4}$ (although the textbook says $\ce{[T]^4}$ which I don't understand)
$\ce{VW4  <-> V + 4W}$ and $\ce{Ksp=[V]^2[4W]^4=[W]^2[4W]^4=256[W]^5}$ (although the textbook says $\ce{256[V]^5}$ but I am pretty sure its equivalent whether it is written in terms of V or W)

FYI my thought process here is that:

Based on the chemical equation RS2⟷R+2S
The concentration of one product (S) is twice that of (R).
So if there is X moles of RS2, and there is X moles of R and 2X moles of S
Hence in the Ksp=[A]^n⋅[B]^m , A=X and B=2X

Now the textbook says

  As $\ce{[P][P]=4[R]^3=[T]^4=256[V]^5}$
  [P] must be the lowest because $\ce{[P]^2}$  has the same value as  $\ce{4[R]^3 and [T]^4 and 256[V]^5}$

I can't get my head around this. I would have thought this proves
$\ce{[P]}$ has the highest value not the lowest. Why is [P] the LOWEST?

E.g. noting that all values are between $0$ and $1$ (as defined in the question)

$\ce{[P]^2=256[V]^5}$  (the other two options are in the middle so don't matter)

If both sides equaled e.g. $0.25$ (which is between $0$ and $1$)

$\ce{[P]^2=0.25 and 256[V]^5=0.25}$

${[P]=0.5}$ and ${[V]=(0.25/256)}^{1/5} = 0.25$

Showing [P]>[V], so [P] (moles/L) is the greatest solubility, not the lowest.

Is anyone able to spot my error?

Question and answer as shown in book below (I have typed up the relevant parts above but sometimes I interpret parts of the textbook question incorrectly (making my stack exchange question invalid or misleading):


texts: Which one of the two is the stronger base: methoxide ion or hydroxide ion?

texts: If we consider the experimentally determined pka values, it looks like hydroxide ion should be the right answer but in many books it has been mentioned that all alcohols are less acidic than water implying that all alkoxide ions are stronger bases than hydroxide ion. This has created a lot of confusion.


texts: Hardness and softness are terms used to describe which aspect of acidic behaviour?

texts:
What do hardness and softness mean?

Is it something to do with the polarisability.


texts: Are there any ADME predictions tools available for Python/RDKit?

texts:
Is there any Pythonic way (a.k.a: a module, an rdkit package, etc) or an API I can use for ADME predictions? I need to prioritize some compounds for purchase/synthesis and some sort of ADME scoring might help me rule out most of them.
I am aware of tools like SwissADME but given the amount of compounds I want to test, it isn't a viable option. Should I train my own model?


texts: How to determine the configuration of an propargylic alcohol?

texts:
I am trying to determine whether the stereocenter of 2-methyl-1-penten-4-yn-3-ol is R or S.

With the ghost atom approach I am determining S:

My supervisor said the stereocenter is actually R configuration. Could someone please explain this and tell me where I went wrong?


texts:
I'm looking to buy some Iodine for various reactions, and noticed that the person who sells it has it in a glass jar with a plastic lid of unknown type.

I'm looking up chemical resistance charts and it says that Iodine, Chlorine and Bromine both work absolutely fine when placed inside of a PTFE bottle, assuming that the Chlorine is not in a gaseous form.
As for Fluorine, one website states that it attacks the plastic severely, whereas the other states that the PTFE is resistant until around the 100°C mark.

These sites are both here and here.

Now when I go look at people asking the question, "How should I store elemental Iodine?", everyone seems to respond along the lines of keeping it in a glass jar with a ground glass joint or PTFE/Teflon lined cap.

However since my research suggests that PTFE alone is capable of storing Iodine, is this a viable option? I would love to know from past experiences, because no-one seems to recommend PTFE on its own on any site I checked. Of course however I will also be storing said PTFE container inside of another non-reactive material container.

I understand that I'm probably better off just storing it in glass containers but I have PTFE bottles lying around and would like to use them if at all possible.

Since this question revolves around the Halogens themselves, could the same be potentially done for Bromine and Chlorine?


texts: Which ions are accounted for in total and net ionic equations?

texts:
There are a number of things I don't understand about ionic equations.

First off, when you do net ionic equations, is it correct that you're only focusing on precipitates? The way I understood it, you put "no reaction" if there are no solid or gaseous products. To clarify, if all of the products of the reaction are aqueous, we look at it as if no reaction had taken place.

Then I went and looked in my book, and that made it seem like all products that weren't covalent were spectator ions, i.e., covalent molecules were the only ones you note.  Now I'm even more confused.


texts:
I was doing a question where I was supposed to predict the shape of the urea molecule $[\ce{H2N(CO)NH2}]$ using Lewis and VSEPR. I identified that the N atoms will have a lone pair on them and so I assigned a trigonal pyramidal shape around N, having the ammonia structure in mind. However when I looked up some 3D structures of the urea molecule it had a trigonal planar shape around N making the whole molecule lie in the same plane. I did some further research and read on wikipedia that

"The urea molecule is planar in the crystal structure, but the geometry around the nitrogens is pyramidal in the gas-phase minimum-energy structure."

What causes this change in geometry when the molecule crystallizes? Does the same thing go for other molecules? Would there have been a way of predicting this as I was solving the question?


texts: How does the reaction of HCl and KMnO4 proceed?

texts:
I don't get how does this reaction of hydrochloric acid and potassium permanganate proceeds:

$$\ce{HCl + KMnO4 -> KCl + MnCl2 + Cl2 + H2O}$$

What I know:

$\ce{HCl}$ dissociates into $\ce{H+}$ and $\ce{Cl-}$.
$\ce{KMnO4}$ dissociates into $\ce{K+}$ and $\ce{MnO4^{2-}}$

What I don't get: How $\ce{MnCl2}$ and $\ce{Cl2}$ can appear there?

Could someone, please, guide me through this reaction, step by step?


texts:
It is not that I didn't google it before asking it here, I could it find it anywhere. My question must be simple but I'm really stuck upon it. How do you name long hydrocarbon chains? Like $\ce{C21H44}$, $\ce{C30H62}$, $\ce{C100H202}$ etc.

I found this when I googled but I didn't quite understand it.


texts:
I've heard about the qst2 Gaussian method but I don't have any licence so I use the free GAMESS-US. Nevertheless, I didn't find any Gamess method which allows a TS finding like qst2. Have you heard about an alternative ?

Thanks


texts: Enantiomers in anisotropic achiral chemical environments

texts:
Consider a functionalised molecular box or cage which has an electrostatic gradient due to positively charged groups one one of its faces. This environment is achiral as there are reflection symmetries

Now place a chiral molecule which for example, has formal charges as shown

Based on heuristic arguments on coloumbic repulsion, we expect the torsional potential energy surface of it and its enantiomer will look like this, where they will be mirror images of each other due to the rotational symmetry:
Now suppose the gradient is something more general such as pH, concentration of a certain reactive species temperature and so on. Then we will suspect that despite they are enantiomers, the anisotropy of the environment will caused them to behave chemically different, with e.g. one of the more positively charged groups will became more reactive due to being positioned near the positive end of the electrostatic gradient of the environment.

What is the terminology that refers to the difference in reactivity due to relative geometric arrangements of moeities between the molecule and its surrounding anisotropic achiral environment?

Any good literature examples where this "rotational selectivity" is investigated or used in the context of chemical synthesis or molecular machines?


texts:
During one of the methods of  polymerization:

  Nylon 6,6 is prepared from polycondensation of hexamethylene diamine
  (HMD) and adipic acid. The repeat unit of the polymer is $\ce{–[NH(CH2)6
NHCO(CH2)4CO]}$. The diamine, which melts at 40.87 °C, is normally used
  in the form of a concentrated aqueous solution. The dibasic acid is
  used in its pure solid form (m.p.= 152.1 °C). In the preparation of
  nylon 6,6 polymer, the first step is a preparation of salt formed from
  a mixture of precise stoichiometric quantities of the two monomers.
  The salt can be prepared by mixing the alcoholic solutions of the two
  components, the pure salt precipitates and is dissolved in water to
  give a solution. Alternatively, the salt can be prepared by mixing a
  dispersion of the diacid in water with a solution of the diamine. The
  aqueous salt solution is prepared so that it has a concentration of
  about 50-60%. For the preparation of nylon 6,6 polymer, the salt
  solution is subjected to evaporation at the boil, possibly at elevated
  pressures, until concentration ≥ 60% are achieved. The concentrated
  salt solution together with a small amount (0.5%) of a molecular
  weight stabilizer is then heated in a reactor under a blanket of
  nitrogen so that temperature increases gradually and pressure reaches,
  typically, 1.73 MPa (250 psi). As water evaporates and temperature
  increases from about 212°C to 275°C, the molecular weight of the
  polymer reaches about 4000. The further reaction is achieved by a
  gradual decrease in reactor pressure to atmospheric pressure and then
  holding the polymer under these conditions for about one hour. At this
  point, the polymer is not quite equilibrated but molecular weights are
  in the range of 12000 to 17000. The process is devised to remove all
  the liquid water present in the salt solution as well as almost all
  the potential water, which may get liberated on the reaction of
  carboxyl (-COOH) and amine end groups present in the polymer. High
  molecular weight nylon for industrial applications is obtained by
  conducting the final stages of melt polymerization under reduced
  pressure (to remove water) or by addition of chain coupling agents (to
  help improve stoichiometric balance). The finished polymer is then
  extruded in the form of a ribbon or strand, quenched with water and
  cut to form chips. After drying, the chips are sent for subsequent
  spinning operation. Alternatively, the polymer may be sent directly to
  a spinning machine without prior solidification. In nylon 6,6 the
  polymerization reaction goes almost to completion.

Now my question is in the above method of polymerization involves formation of aqueous nylon salt from pure salt. I want to know why the precipitated pure salt isn't converted to polymer but is made aqueous and then converted to polymer? Isn't there anyway of forming the polymer from pure nylon salt (fully crystal dehydrated salt) instead of the aqueous one from the reactants?

Note: I'm ok with reacting the pure salt with any chemical substance to form the polymer.


texts: Are there practical chemical reactions that do mechanical work without heat or electricity?

texts:
Every day we use chemical reactions to perform mechanical work by creating either heat (e.g. in a piston engine) or electricity (batteries). I know muscles perform work by taking stored chemical energy and converting it directly into mechanical force.

Other than in organic chemistry, are there any examples of chemical reactions that we use to perform mechanical work without the intermediate step of harnessing the heat or electrical potential created by the reaction?


texts: Why does a smaller amount of propanol burn slower than a much larger amount?

texts: Why does $30~\mathrm{mL}$ of $\ce{C3H7OH}$ burn in 1 second (inside a water jug) compared to a sixth of the amount: $5~\mathrm{mL}$ of $\ce{C3H7OH}$ (on a plate) burn in 180 seconds? Why does the smaller amount take longer to burn the propanol?


texts: How does black CuO impart a green color to glazes and glass?

texts: I read from a source that cupric oxide (CuO) imparts green to blue colour to glazes and glass. But CuO is black in colour. How is this possible?


texts: Is iron in the brown ring compound in a +1 oxidation state?

texts:
In the standard brown ring test for the nitrate ion, the brown ring complex is:
$$\ce{[Fe(H2O)5(NO)]^{2+}}$$

In this compound, the nitrosyl ligand is positively charged, and iron is in a $+1$ oxidation state.

Now, iron has stable oxidation states +2 and +3. Nitrosyl, as a ligand, comes in many flavours, of which a negatively charged nitrosyl is one.

I see no reason why the iron doesn't spontaneously oxidise to +3 and reduce the $\ce{NO}$ to −1 to gain stability. But I don't know how to analyse this situation anyway. I think that there may be some nifty backbonding increasing the stability, but I'm not sure.

So, why is iron in +1 here when we can have a seemingly stable situation with iron in +3?


texts: Do carboxylic acids form hydrates like aldehydes and ketones?

texts:
Having learned that aldehydes exist in equilibrium with their hydrate form -

Do carboxylic acids do the same in a water solvent and form a hydrate with 3 $\ce{OH}$ groups and one alkyl group?


texts: Predicting the products of the radical chlorination of propane

texts:
Question:

When propane reacts with chlorine, two different monochloropropanes are formed.
a) Name and show the full structural formulae of the two products.
b) What kind of isomerism is shown?

Based on my understanding, the answer for part a is $\ce{2C8H18 + Cl2 -> 2C8H17Cl +H2}$.
Name: chloropropane, formula: $\ce{CH3CH2CH2CH2CH2CH2CH2CH(Cl)}$.
For part b, is it structural isomerism? Are my answers correct?


texts: How many Au atoms can be extracted from 0.250 L of seawater?

texts:
Gold is present in seawater to the extent of 0.15 mg/ton. Assume the density of seawater is 1.03 g/ml and determine how many gold atoms could be extracted from 0.250 L of seawater.

($\pu{1 ton}=\pu{2000lbs}, \pu{1kg}=\pu{2.205lbs}, \pu{1 mole}=\pu{6.022E23 atoms}, \text{1 mole of gold}=\pu{197g}$)

I just multiplied everything together using dimensional analysis and got $5.2\times10^{14}$ atoms of Au per liter of seawater, but they want how many atoms of Au in $\pu{0.250L}$ of seawater so I just multiplied $5.2\times10^{14}$ by $0.250$ to get $1.30\times10^{14}$ atoms of Au per $\pu{0.250L}$ of seawater. Can you simply multiply everything together like this? When can you do this and when can't you?


texts: Why on changing temperature of a reaction its activation energy and pre-exponenetial factor do not change significantly?

texts: My teacher told me that on changing temperature of a reaction, its activation energy ($E_{a}$) and pre-exponenetial factor ($A$) do not change significantly and hence we can assume them to be constant on changing the temperature. But my question is why? Why don't they change significantly? Even in the graph given in my textbook (given below), on changing temperature they have assumed activation energy to be constant. Is it really true? Please clarify. Would greatly appreciate it!


texts: Can corrosion from hydrogen peroxide solution model the corrosion protection activities of Al coating?

texts: Immersion in hydrogen peroxide can make steel corrode very fast. However, the coated steel resisted the corrosion attack for a span of time, and as time passes, the coating becomes thinner. Some got removed from the subtrate. Can this mechanism be a model for the corrosion protection of the Al coating for research studies? Does this reflect the behavior of metal coating in immersion with other corrosive media like NaCl?


texts:
I'm not so sure how this mechanism is supposed to go. Could anyone provide some pointers?

The answer is supposed to be:

In particular, I'm confused about how to break up the two esters.


texts: What is the difference between temperature and thermodynamic temperature?

texts: My course book says that kelvin is the unit of thermodynamic temperature, then what is the difference between temperature and thermodynamic temperature.


texts: How to calculate the average size of cubic crystals of KCl powder?

texts:
The total area of $\pu{0.5 g}$ sample of $\ce{KCl}$ powder is measured to be $\pu{1620 cm2}$. If the powder consists of tiny cubic crystals, what is the average size of these crystals?

I'm studying for a physical chemistry final and am not sure how to do this practice question.
I know that the density is
$$\delta = \frac{m}{A},\label{one}\tag1$$
where $m$ is the mass and $A$ is the surface area, so do I just find
$$A=\frac{m}{\delta}$$
to find the average "size"?
Or do I use \eqref{one} and then find out what the unit cell structure of $\ce{KCl}$ powder is and use that to estimate what the surface area of the crystal is?


texts:
is there a general word equation so I can learn how to write out the following:

With chlorine, it seems to be: Hydrocarbon + Chlorine ---> ____ + HCL

With Hexane, it seems to be: Hydrocarbon + Br ---> ____ + HBr

I am not sure how to derive the first part of the final reaction (____)

It seems that methane has lost one hydrogen atom.

It seems that hexane has lost one hydrogen atom too.

Does that mean, if it was say Pentane with Chlorine, the first part of the final reaction would be CH4CL (not ch5cl) ? Likewise, would Pentane with Bromine be C6H12BR (and not c6h13br)

It feels like i'm rote-learning a skill, wonder where my knowledge is missing hmm..


texts: What is meant by 'penetration of atomic orbitals'?

texts:
While studying atomic structure, I have faced this term very often. I assume this is a very detailed type question!
But if anyone can please provide just the preliminary idea about this, it will be helpful.


texts:
This is a rather physics question but I wanted to get an insight from a chemistry perspective. I heard from some that you can beat the speed or go faster than it but is that really true. Physicists as we all know look at the theoretical possibilities but what is your insight from a chemistry-ish view.

Here and here for more information.

If we can then how much more faster is it? I heard one view into this that goes along the lines of:

If you distorted space and moved it then you would be light-years away from where you started. This seemed very dumb at first but as I thought about it is this anyway possible.


texts: How do we get NaClO3 in the reaction between Cl2 and NaOH?

texts:
From problem no. 4080 in a Russian example exam set:

$$\ce{6NaOH + 3Cl2 -> NaClO3 + 5NaCl + 3H2O}$$

How do we get that $\ce{NaClO3}$? I can't seem to guess. I found this explanation on YouTube, but there the products are different:

$$\ce{Cl2 + 2NaOH -> NaCl + H2O + NaClO}$$

In both reactions, there is twice as much sodium chloride as there is chlorine. How do the two additional oxygens connect to the chlorine?

P.S. A related question - thanks, Nilay Gosh.


texts:
I have a question regarding nano coatings based on the formula "modified $\ce{SiO2}$".

I have been told that $\ce{Al}$ bottles react with substances with a $\mathrm{pH}$ value below 3 or above 9. When the substances are not within these limits, it will form $\ce{Al^3+}$ which will cause the $\ce{Al}$ bottle to corrode, if I understand it correctly.

My question is therefore, when does this corrosion begin, how much time does it take, and can it ruin my nano coating effects?

My supplier of the $\ce{Al}$ bottles also has a bottle that they call "Chemical pesticide insecticide agrochemical pharmaceutical Aluminum bottle", does this bottle create any difference regarding the possible reaction with $\ce{Al}$? Perhaps it corrodes at a lower or higher $\mathrm{pH}$ value?

Also when my supplier of the coatings indicates the products has a chemical stability between 1-13, what does that mean?


texts: My undergraduate lab is currently doing a project in which we have to separate inorganic compounds from organic compounds, identify each compound, and quantify how much of each compound there is. We've identified that the inorganic compounds are NiCl2 and CoCl2, and quantified them using Beer's Law. However, our project specifications say we need to come up with two ways of quantifying them, and we're stumped on finding a second way. Is there a reaction that can possibly titrate one of the compounds without having the other compound interfere, or perhaps separate them and then weigh them using a gravimetric approach? The problem is that the two compounds seem to have the same solubility properties so we don't quite know how to proceed. Thanks!


texts: Volume Element in the Integral for Variational Method

texts: I'm learning how to use variational method to calculate the energy of ground state helium. I understand how we can set up a trial wavefunction that is a product of two hydrogen-like wavefunctions; however, when finding the integral $\int_{a}^{b} \phi H \phi dr_1dr_2$ (for $\phi=\phi_1(r_1)\phi_2(r_2)$), what would the volume element be? Would it be $16\pi^2 r_1^2 r_2^2$? I'm assuming the denominator is one for normalized wavefunction of hydrogen-like atom.


texts:
You wish to design an airbag for a car. The gas that is released must be at a pressure higher than that of air – $\pu{110 kPa}$ at a temperature of $\pu{22 ^\circ C}$. The bag that you develop can expand to a volume of $\pu{45.5 L}$. What quantity of sodium azide $\ce{NaN3}$ should be used to generate the required mas of $\ce{N2}$ gas?

I've been given this question on my revision sheet. So far I've figured out using Boyle's law that I need 2 mol of $\ce{N2}$ gas. However, I am unsure of how to transfer this over to the $\ce{NaN3}$ and use the ratio or what not to find the number of moles there.


texts: Can compressed CO2 sprayed onto a hot mass/liquid be an effective means to cool it?

texts:
I thought the answer was obvious, but endless google searching has revealed nothing but speculation and people who have completely conflicting opinions. Some people say $\ce{CO2}$ absorbs no heat, others say it can cool things extremely rapidly. Anyone who has ever had compressed $\ce{CO2}$ sprayed on themselves or on hands knows it can cause very rapid drop in temperature on what ever it hits very fast.

So, if I have a really hot mass of liquid, would spraying compressed $\ce{CO2}$ on it be an effective means of freezing/solidying the mass? - Assuming the liquid is well above room temperature (100+) and turns to a solid after a 20-30 degree drop in temperature?

I understand why the $\ce{CO2}$ is cold coming out of the tank, as it is decompressed, but is it effective at absorbing heat?


texts: If $\ce{H2O}$ dissociates as follows: $$\ce{2H2O <=> H3O+ + OH-}$$ and not in this way: $$\ce{H2O <=> H+ + OH-}$$ why is the equilibrium constant: $$K_{eq}=\frac {\ce{[H+][OH-]}} {\ce{[H2O]}}$$ and not: $$K_{eq}=\frac {\ce{[H3O+][OH-]}} {\ce{[H2O]^2}}$$


texts: In Wolff rearrangement, what is the role of $\ce{Ag_{2}O}$ in migration of alkyl/aryl group?


texts: How to calculate the gas-liquid interaction for dissolved HNO3 in water with air?

texts:
Thanks for reading this and (maybe) helping me in advance!

I have to face the following problem:
I have got $\ce{HNO3}$ dissolved in water (roughly $\pu{50\%}$) and I want to know how much $\ce{HNO3}$ will be in the air directly above it. I got classes about liquid-gas phases, but it was a long time ago and therefore I am not capable anymore to engage such a question.

As far as I can recall the pressure and temperature are important, which are $\pu{1 atm}$ and $\pu{20-25^oC}$ (but I want to calculate it for a range between $\pu{20-100^oC}$). I can imagine that it might be hard due to the fact that a part of the $\ce{HNO3}$ will split into ions $\ce{H+}$ and $\ce{NO3-}$ (till it reach its pKa), so that will give an equilibrium towards the liquid phase. But in the end there must be some $\ce{HNO3}$ in the air due to gas-liquid equilibrium.

Is there anyone that can tell me how to calculate this or how to engage this question? Any advice is appreciated!

Edit: During further investigation I found out that the problem is even more complicated since $\ce{HNO3}$ will split into $\ce{NO}$, $\ce{NO2}$ and $\ce{N2O4}$ (nitrous gases). If possible I want all the concentrations of these gases at those temperatures.


texts: Does benzene's resonance structure allow it to enter DNA?

texts:
According to this link, benzene is able to insert itself into the human DNA. It isn't an authoritative source and appears to be quite biased, so I'm wondering if there's any truth to this.

  The resonance hybrid structure of the benzene molecule causes it to have electrostatic potential, be very stable, and insert itself into human DNA. Taken together, these molecular and electrical characteristics of benzene make it carcinogenic to humans.


texts: What is the mechanism behind the decomposition of enediol phosphate intermediate to methyl glyoxal?

texts: I can't seem to figure out the mechanism for the decomposition of enediol intermediate (in glycolysis) to methyl glyoxal? How does the phosphate group get replaced by a hydrogen?


texts: What makes polyimides good polymers for fibers?

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Wikipedia says polyimides are known for “thermal stability, good chemical resistance, excellent mechanical properties”. I guess that's why they're used industrially as fibers.

But where do they derive there good stability (thermal, mechanical and chemical) from? How do these properties differ from, e.g., polyamides?


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Node is a region in atomic orbital where there is no possibility of finding electrons. That is no electron can be found there (region of $\psi^2 = 0$)
Take example of say $\mathrm{2s}$ orbital: as electrons cannot be found in node, then how can it spend time in first lobe (spherical) and in second lobe (spherical) separated by nodal region where it cannot go?

And because of course it is electron and its possibility to be found that marks up possible boundary of orbital.


texts: Why is the cis isomer of 1,3-dimethylcyclobutane more stable than the trans isomer?

texts: I expect there to be more steric repulsions between the two methyl groups if they are on the same face as each other. Why is this not the case?


texts: How does pH affect the degradation of ascorbic acid (vitamin C)?

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I know that vitamin C degrades over time (as I understand through oxidation). However, I am having trouble understanding how changing the pH of the solution in which the vitamin C is affects the rate at which the vitamin C degrades.

Among others, Roig et al. [1] demonstrated that there is indeed a change in degradation based on pH.

References

Roig, M. G.; Rivera, Z. S.; Kennedy, J. F. A Model Study on Rate of Degradation of L-Ascorbic Acid during Processing Using Home-Produced Juice Concentrates. International Journal of Food Sciences and Nutrition 1995, 46 (2), 107–115. https://doi.org/10/fgwc5c.


texts: What is the chemical reason talc is used in water-based paint and not in solvent based paint?

texts: As I understand, paints & coatings use talc predominately in water-based products and not in solvent-based products. Why is this? Is it because the solvent-based products don't need fillers? Or do they already have the characteristics that talc would provide?


texts: I am having problem with this question including topics of redox reactions and charges

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What is the oxidation number of $\ce{Fe}$ in $\ce{K4[Fe(CN)6]}$?
This seems to be a pretty easy problem. Just input the oxidation numbers of everything and equate for 'x'. But the problem is that I don't know the charge on the Cyanide ion right there. Now, I knew from doing many questions that $\ce{Fe}$ usually has +2 or +3 so i guessed +2. But I don't want to be guessing on the actual day.
I essentially need to know the best way to find charges on polyatomic ions because there's just loads of them and I don't think I can remember over 300 oxidation states. I know the charge can be calculated by adding up Oxidation states but most elements have variable Oxidation states too so I am really confused.
Even if you know a certain website that may be useful, please link it. Any help is appreciated.


texts: Calculating the density matrix from a WFN file

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I want to calculate the density for the $\ce{HCN}$ molecule. This molecule has 14 electrons and thus 7 occupied molecular orbitals. I have a .wfn file which includes 8 parts, where each of them has 14 rows and 5 columns (due to 5 basis functions). The first part belongs to the basis functions (exponents) and the 7 other parts contain coefficients for each of seven MO's. How can I calculate the electron density using this file? Generally I have used the electron density formula based on the Roothaan expansion introduced in Szabo's textbook, namely:

$$
P_{\mu\nu} =2\sum_{a=1}^{N/2} C_{\mu a}C_{\nu a}
$$

where $a$ runs over the number of electrons, though I have seen in several codes that $a$ is considered as the number of occupied MOs. $\mu$ and $\nu$ stand for the number of basis functions (5 here).

Should I use all 7 parts of the coefficients to obtain the electron density of the $\ce{HCN}$ ground state, or is the first part which has the minimum energy sufficient?


texts: why is HClO a better oxidizing agent than HClO2, HClO3, HClO4?

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Why do the oxoacids of chlorine have the following order of oxidizing power: HClO > HClO2 > HClO3 > HClO4 ?
When I search it online, many posts say "because the oxidation state of Cl in HClO is the smallest, so it has the best tendency to be reduced."

I don't really understand the explanation. Can someone please elaborate on it?

Also, I found that

Fe3+(aq) + 3e- → Fe(s)   E°(V) = -0.04V

Fe2+(aq) + 2e-→ Fe(s)    E°(V) = -0.44V

Doesn't the above contradicts the explanation?


texts:
I'm trying to find an explanation for the letter codes (X, A, B, C, etc) when you get a term symbol like this

$$X\,{}^3{\Sigma}^-_g$$

Can anyone point me to some literature that explains these letter codes?


texts: Electrophilic Aromatic substitution reactions of aromatic compounds

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Benzene and substituted benzene (phenols, aromatic ethers, benzaldehyde, aromatic ketones like acetophenone, benzoic acid, aniline and nitrobenzene) generally can undergo electrophilic Aromatic substitution reactions.
Now among all of these only benzene and aromatic ethers can undergo Friedel-Crafts alkylation reactions (or I'm wrong?).
My question is do all of the Aromatic compounds undergo halogenation,nitration and sulphonation cause these reactions as far as I know fall under electrophilic Aromatic substitution reactions.


texts:
I've heard quite a few times that the chromate and permanganate have a $d^3s$ configuration. Also, their colors arise due to a rapid switching of electrons between the oxygen and metal atoms.

I don't really understand the 'rapid switching' part--it's obvious why it can give color, but I fail to see why there is a need for such a switching-what's so special about $\mathrm{Cr}$ and $\mathrm{Mn}$? (I also do not know what the switching exactly is)

An explanation of $d^3s$ would be appreciated, though not necessary.


texts: Can flexible plastics have reflective coating (vacuum metalized)?

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Is it possible to achieve an optical mirror coating to a flexible plastic part?

If vacuum metalization is possible, would the reflective coating layer be durable enough to withstand the bending of a flexible plastic such as polyurethane or a thermoplastic elastomer, without cracking over time?