texts: Check My Beginner's Guide to Shells, Energy Levels, Subshells, and Orbitals

texts:
I am a beginner trying to summarize what I've learned about:

Shells
Energy Levels
Subshells and
Orbitals

all at the high school level.
Unlike related threads, I'm going to try to:

Define each word and state a few key properties of each.
Highlight what is most important for beginners.
Summarize all of that in a table.

Please let me know how I've done!
Thanks!

tl;dr Summary: Electrons move within orbitals which are in subshells which are in shells which are in atoms.

Shell aka Energy Level
Below atoms, shells are the largest grouping of electrons beginner chemists should care about, and among those, the innermost two shells are most important to beginners.
They correspond to periods (rows) on the periodic table of the element.

In the 3rd period, all elements have 3 shells.
In the 5th period, all elements have 5 shells.
In the $n$th period, all elements have $n$ shells.

Generally speaking, the larger $n$ means:

The shells are farther away from the nucleus and thus the electrons in it are less attracted to the nucleus.
The shells can hold more electrons, i.e. an atom of that element requires more valence electrons to be stable.

Subshell
Each shell consists of at least one subshell. Below atoms, this is the second largest grouping of electrons beginner chemists should care about.
There are 4 types of subshells: $s$, $p$, $d$, and $f$. For beginners, the $s$ and $p$ subshells are the most important.
The notation for shells and subshells:

$1s^2$ means the 1st shell's $s$ subshell has 2 electrons in it.
$4d^5$ means the 4th shell's $d$ subshell has 5 electrons in it
$AB^X$ means the $A$th shell's $B$th subshell has $X$ electrons in  it.

Note: This notation does not specify which orbital those electrons are in... but that info does not matter much to beginners.
Orbital
An orbital is an actual path (probability distribution function, PDF) that either 1 or 2 electrons can be whizzing through at a time. This is the smallest grouping of electrons beginner chemists should care about. The math underlying that PDF is not critical for beginners.
Each subshell consists of at least one orbital.
THE BIG TABLE
Feel free to edit the table. :)


texts: Why there is charge on the elements, in the dative bonding?

texts: According to the definition of dative bonding electrons are shared which are given by one of the atoms, so if the electrons are shared so how come there is charge on the elements in the dative bonding?


texts: What is the temperature of evaporating water (not boiling)?

texts:
The vapor pressure of water at $\pu{70 ^\circ C}$ is $\pu{233.7torr}$.
If I were to put a temperature probe directly above the liquid water, what would it read?

In other words, does a water molecule need to have $\frac32kT$ (where $T=\pu{373 K}=\pu{100 ^\circ C}$) to escape the liquid?


texts: Why is the production of aramid fibers expensive?

texts:
When comparing knitted fibers for the production of clothing, aramid based fibers trade at many times the price of classics synthetic fibers per $\mathrm{m}^2$.

Despite the limited supply of aramid fibers, what are the core drivers in production costs when compared to classical synthetic fibers?


texts: What type of bond would be formed if dyz orbitals overlap along the z axis?

texts: I know that when two $\ce{p_z}$ orbitals overlap in a particular direction - along the z axis - they form a sigma bond. Now, if two $\ce{d_{yz}}$ orbitals overlap in same direction, which type of covalent bond would be formed?


texts: Which poison was used in the failed attempt to assassinate Khaled Mashal of Hamas?

texts:
This question is both historical and chemistry-related, but I'm posting it here because I am more interested in the chemical part:

In 1997, Israel tried to assassinate Khaled Mashal, a high-rank official of Hamas. This was to be done using an extremely potent poison that was supposed to be sprayed on him topically and kill him within a few days without a trace (a "quiet" murder).

I searched for the name of this poison, but I was only able to find out that it was a modified version of the drug Fentanyl (here, page 16). It was probably an internal formulation of the Mossad, but I was wondering if the formula was ever publicly released or if anyone knows how Fentanyl's structure was modified in order to make it so deadly upon contact.


texts: Comparing acidity of p-chloro benzoic acid and p-fluoro benzoic acid

texts:
I am really confused about comparing the acidity of p-chloro benzoic acid and p-fluoro benzoic acid.

The question here doesn't have a conclusion and the discussion here is confusing.

My Try:

-F and -Cl being +R groups create negative charge on o- and p- positions with respect to them.

-F having greater +R effect tends to produce greater negative charge on the positions ortho and para to it

-Cl having a greater +I effect tends to create greater amount of $\delta-$ charge than -F

The acidity of the molecule depends on the negative charge on the starred carbon atom (greater negative charge$\implies$less acidic):

My Confusions:

 Is inductive effect strong enough to act para to the specific group?

 Which among -F and -Cl will produce greater cumulative negative charge on the starred carbon atom, and how?

The answer given:

p-chloro benzoic acid is more acidic than p-fluoro benzoic acid, contrary to the order existing between p-chloro benzoic acid, p-bromo benzoic acid and p-iodo benzoic acid


texts: Plotting ΔG vs Temp for Electrochemical Reaction

texts:
I’m doing an electrochemistry lab that requires me to construct various galvanic cells in an attempt to solve for $\Delta H$, $\Delta G$, and $\Delta S$ values of an unknown. During one part of the experiment, I had to heat a cell to a temperature of 70 °C and record its voltage in 15 degree increments until the temperature reached 10 °C.

The cell I am using to perform this step on is represented by the equation:

$\ce{Zn + Sn^2+ -> Zn^2+ + Sn}$

After performing the procedure, I’m getting concerned that my data may be inaccurate. Theoretically, I was using 0.1 M concentrations of each solution in the cells. According to the Nernst equation, it seems that the voltage or potential of the cell should not be affected by a change in temperature if the concentrations are equal because $\ln(0.1/0.1) = 0$.

However, according to my professor, I should be seeing a linear relationship when I plot $\Delta G$, calculated from the voltage measurements I took, vs the temperature in K.

My question is, theoretically, what should happen to the voltage as I heat the cell, assuming that the concentrations of the solutions were off? I’ve calculated the $\Delta S$ value based on the standard values listed for these entities and I’m getting a value of −85.18 J/(K mol).

Calculation: $\Delta S = (-112.1 + 51.55) - (41.63 + -17.0) = -85.18\ \mathrm{J/(mol\ K)}$

Based off of this result, it would appear that the slope of this plot must come out to be a positive value because $m = - \Delta S$. Does this mean that I should be seeing an increase in voltage as temperature decreases? Regarding the $\Delta H$ of this reaction, which is represented by the Y-intercept (b) of the equation of the best fit line for my data, it appears I must also have a negative value of −145090 (in units of J) based upon the calculation I did for this, also using standard values.

Calculation: $\Delta H = (-153.89 + 0) - (0 + -8.8) = -145.09\ \mathrm{kJ/mol}$

I’ve tried to be as detailed as possible in describing by question, and hopefully it makes sense. I’m just getting confused on what the data should look like. Unfortunately, its not possible for me to redo the experiment. Please note that this is for my own understanding, I will not submit the assignment with fixed data. I appreciate any assistance that anyone can offer me.


texts: A Spectrophotometric technique to evaluate Vitamin C concentration in Citrus Fruit

texts:
Is there a visible spectrophotometric technique that can gage the concentration of vitamin C in solution? I plan on boiling different citrus fruit in water, and taking aliquotes of the boiled solution to determine total leached vitamin C. I’ve found a couple of UV spectrophotometric techniques, but wasn’t certain if those techniques could carry forward using a visible spectrophotometer. Those sources also didn’t specify what the vitamin C concentration range was for a Beer Lambert’s Law assay.
Would spectrophotometry be possible? Or would it be more feasible to perform a redox titration of vitamin C (ascorbic acid) using iodine?


texts:
I have a question concerning simultaneous sampling of water and gas phase.

The situation is a pipe (diameter somewhat around 15 cm) where a mixture of water and gas is flowing through (two-phase flow). Assuming that the flow is separated and the gas phase is moving on top, what will happen if I open a sampling tap at the bottom of the pipe? The flow is induced by a pump and the pressure in the system is above ambient (20 bar).

My assumption is, that I only sample the water and the gas phase on top will not leave the pipe unless I allow the gas phase to "connect" with the tap by extracting a big amount of fluid.

The problem is maybe comparable to a bottle of sparkling water, where I drill a small hole at the bottom. Will I only sample the fluid phase or will I sample a mixture of both?

I hope somebody has an answer. Thanks in advance!


texts: What is the structure of iodide of Millon's base?

texts:
In qualitative analysis, $\ce{NH4+}$ ions are confirmed using Nessler's         reagent:-

$$\ce{NH4+ + 2[HgI4]^{2−} + 4OH− → HgO·Hg(NH2)I ↓ + 7I^{−} + 3H2O}$$

The brown precipitate formed is called iodide of Millon's base.  It is also written as  $\ce{3HgO.Hg(NH3)2I2}$ and as $\ce{NH2.Hg2I3}$. (wikipedia).

But its structure is present differently in different sites:-

Source 1 - ionic form

Source 2  - Here the reaction is given differently:-

$$\ce{([K2]HgI4 <=> 2KI + HgI2) * 2}$$
$$\ce{HgI2 + NH3 -> Hg[NH2]I + NH4I}$$
$$\ce{Hg[NH2]I + HgI2 -> NH2Hg2I3 }$$
$$\ce{[K2]HgI4 + 2NH3 -> NH2Hg2I3 + 4KI + KH4I }$$

structure -

Source 3- non ionic form

Source 4 - Hydrate form; Here also the reaction is different:-
$$\ce{[K2]HgI4 -> 2KI + HgI2}$$
$$\ce{HgI2 + NH3 -> Hg[NH2]I + HI}$$

This site also says that its structure is still uncertain. Various other structure has been proposed:-

So, what is the correct reaction, correct formula and correct structure of iodide of Millon's base?


texts: Does sodium cyanide react with water, and can it cause an explosion?

texts: According to some conspiracy theory, the explosion that happened last year in Tianjin (China) wasn't caused by sodium cyanide. Can sodium cyanide react with water, and can it cause an explosion if you have 700 tons of it?


texts:
I have a few cleaning products and after I looked on the ingredients, they feel pretty redundant:

Bath cleaner: Less than 5% anionic tensides, anionic tensides, scent.
Shower cleaner: Less than 5% anionic tensides, anionic tensides, scent.
Glass cleaner: Less than 5% anionic tensides, color components, helper components, scent.
Kitchen cleaner: Less than 5%: anionic tensides, scent, lime, linalool.

Others seem to have significantly different chemicals in them:

Bref Power Universal Cleaner: Less than 5% soap, non-ionic tensides, anionic tensides. Additionally: Scent (dutylphenyl methylpropional, citronellol, lime), preservative (sodiumhydroxymethylicinat)
Frosch pH-neutral cleaner: 5–15% anionic tensides, less than 5% amphoteric tensides, preservatives (sodium benzonate, benzyl alcohol), scent, color.

The “kitchen cleaner” has a distinct scent and cleans much better. When I get it on my hands, it feels really slippery, so perhaps it is alkaline? The “bath” and “shower” cleaner seem to be virtually the same except for the printing on the bottle.

I know that in order so solve grease with water, one needs to have a solvent that has both polar and Van der Vaals bonds. Ethanol would do, for instance. For limestone, one needs to have some acid, like citric acid (my chemistry teacher one said that he uses diluted hydrochloric acid, but that's another story).

Are those cleaning products really all that different? Is “anionic tensides” broad enough that there could be a significant difference between them such that using one or the other actually makes more sense?


texts: Why does the Born equation give the Gibbs free energy of solvation rather than enthalpy of solvation?

texts:
The Born equation gives the difference in energy required to charge a particle in a vacuum and in solution which results in the work required to transfer an ion from a vacuum into solution. It is derived thus:

$$w=\int_0^Q\frac{Q}{4\pi\epsilon r}dQ-\int_0^Q\frac{Q}{4\pi\epsilon_0 r}dQ$$
Where $\epsilon=\epsilon_r\epsilon_0$ ($\epsilon_r$ is the relative permittivity of the medium/solvent - a dimensionless quantity). $w$ is work done.

$$w=\frac{1}{4\pi\epsilon r}\int_0^QQdQ-\frac{1}{4\pi\epsilon_0 r}\int_0^QQdQ$$
$$w=\frac{Q^2}{8\pi\epsilon r}-\frac{Q^2}{8\pi\epsilon_0 r}$$
$$w=\frac{z^2e^2}{8\pi\epsilon r}-\frac{z^2e^2}{8\pi\epsilon_0 r}$$
So for a mole of ions the work done is equal to:
$$\frac{N_Az^2e^2}{8\pi\epsilon r}-\frac{N_Az^2e^2}{8\pi\epsilon_0 r}=\triangle_{solv}G^{\theta}$$
My textbook seems to suggest that the last step makes it Gibbs free energy of solvation rather than just work done. I have two issues with this. Firstly, why is it Gibbs free energy and not, say, enthalpy of solvation or internal energy of solvation? Secondly, why would scaling the number of ions to one mole make it into Gibbs free energy? Isn't Gibbs free energy an extensive property with units of Joules? I know that the Gibbs free energy (and enthalpy) are often given with units of $Jmol^{-1}$ but isn't this strictly molar gibbs free energy/chemical potential?


texts: Should the anode potential be increased or decreased to generate current?

texts:
I am taking a course on fuel cells and we were talking about the activation energy needed to start a chemical reaction.

I would think that the answer to this question is that the anode potential should be increased to generate current so less energy is needed to begin the reaction.

Is this right? Or am I way off track.


texts: Why is white phosphorus considered to be the standard state of phosphorus although it is only metastable? Red phosphorus is thermodynamically more stable than white phosphorus, yet it is not the standard state.


texts: Salting out worsens extraction efficiency

texts:
I'm currently writing a thesis about using dispersive liquid-liquid microextraction DLLME for extracting nitramines from aqueous solutions. We've been using octan-1-ol as the extractant and HPLC for analyzing extracted samples. Since the extraction efficiency was generally poor (max amount recovered was 36% for CL-20 samples) we've decided to try adding 500 mg NaCl to the samples, which all consisted of:

100 ul of nitramine in ACN solution, 1 mg/ml
400 ul ACN
9,5 ml H2O

We thought that salting out would decrease the amount of nitramine dissolved in water, so more of it would be extracted to the octanol phase, but it actually made things worse, as each of the substances studied (RDX, HMX, TEX, CL-20) showed a drop of about 1/3 relative to the amount extracted w/o adding NaCl. I'm very curious as to why this happens, but I haven't found any articles on the Internet that talk about the drawbacks of salting out. Any ideas?


texts: Double alkylation of benzene to form tetralin

texts:
I have been asked to suggest a synthesis for the following compound (tetralin) from benzene:

I am unsure how to do this. It surely can't be Friedel–Crafts alkylation because of carbocation rearrangement and polyalkylation, right? Possibly a double acylation followed by a double reduction? Is there an issue with this; maybe a competing aldol type reaction in the double acyl chloride reagent that would be required.


texts: How to determine thickness of Fe2O3 deposited on HOPG?

texts:
What would be the reasoning between choosing ellipsometry vs AFM to determine thickness of a iron oxide film deposited on highly oriented pyrolytic graphite?
Im new to the materials world and am trying to understand why I would pick one over the other. Any insight would be appreciated.


texts: How to assign oxidation number of sulfur in thiocyanate anion?

texts:
Recently I was trying to balance a redox chemical equation:

$$\ce{CuSCN + KIO3 + HCl <=> CuSO4 + KCl + HCN + ICl + H2O}$$

The equation is in principle simple to solve; one element ($\ce{I}$) is reduced and two elements ($\ce{Cu}$, $\ce{S}$) are oxidized. The number of exchanged electrons in both cases must be the same. However, my problem is that I don't know how to assign the oxidation number to sulfur in a thiocyanate anion.

Later, I solved the equation using the matrix method and via obtained reaction coefficients ($4$, $7$, $14$, $4$, $7$, $4$, $7$, $5$) and concluded that the oxidation state of sulfur in thiocyanate is zero. This result is very surprising, because the oxidation number zero in heteroatomic molecules is not common.

My questions are:

How to assign the oxidation number in such cases?
How is it possible that oxidation number of an atom bound to a more eletropositive atom is zero?


texts: Why does the dielectric constant of a solid increase due to a Frenkel defect?

texts: In crystalline solids, an atom may be displaced from its original position in order to create a vacancy in the original location. This is referred to as a Frenkel defect. Why does this defect result in an increase of the dielectric constant of the solid?


texts: Pseudochirality with more than two groups on one carbon atom

texts:
Can pseudochirality be considered when three or four groups on the carbon atom are constitutionally the same, but configurationally different?

For example, when the C atom is bonded to one H, and then three more structurally identical groups with 2 chiral C each - in configurations R,R and S,S and R,S respectively - then by assigning each of the 4 groups a priority value (since they are all different - though 3 have the same structure) we can assign a configuration to this C atom.


texts: How to draw resonance structures for CH3COCN

texts: What are the resonance structures of $\ce{CH3COCN}$ molecule?


texts:
I was just pondering about the reaction mechanism of Cannizzaro reaction.

$\ce{H2C^{+}-O- + OH- -> H2C(OH)O-}$

$\ce{HCHO + H2C(OH)O- -> H3CO- + HCOOH}$

$\ce{H3CO- + HCOOH -> HCOO- + H3COH}$

I wondered why in 2nd step instead of receiving $\ce{H-}$ from $\ce{H2C(OH)O-}$; $\ce{H2C^{+}-O-}$ wouldn't react with NaOH to form $\ce{H2C(OH)ONa}$.

I don't think this compound will be able to exist. But don't know why! Everything seems right about it.


texts: Rate of reaction of silver salts of carboxylic acids having different alkyl groups towards Hunsdiecker Reaction

texts:
Hunsdiecker reaction follows free radical mechanism but it is given that rate of reaction with different alkyl groups (R) attached to silver salts of carboxylic acid follows the order as follows

Primary > Secondary  > Tertiary  (Rate)

But free radical stability is exactly opposite!

Primary < Secondary < Tertiary  (Stability Free Radicals)

What can be the reason for this kind of trend in this reaction?

I'm attaching the reaction mechanism for reference.


texts: Regioselectivity of alpha halogenation of ketones

texts: Why does alpha halogenation of a ketone in acidic conditions happen at the more substituted alpha carbon atom, and in basic conditions at the less substituted alpha carbon atom?


texts:
Question

What chemical is used to stabilize berry juices used as wood stains?

Aim & tries

I am trying to make a stain for a snowboard design and coloration of the wood. I used pure pokeberry juice, but almost all of the color vanished after sending through the heat compressor. Now I need to find a way to stabilize the berry substance and I am unsure of where to start.


texts: Using solubility guidelines to predict a reaction of two ionic, water-soluble salts

texts:
Will a reaction occur in the following case? If so, write a net ionic equation for it:
$\ce{(NH4)2SO4 (aq) + ZnCl2 (aq) -> ?}$

The book says that all possible combinations of positive and negative ions lead to water soluble compounds, all of the ions remain in solution. No reactions occur.
Now I am a little confused. Why didn't $\ce{(NH4)2}$ join with $\ce{Cl2}$ and why didn't $\ce{SO4}$ join with $\ce{Zn}$? Or did they?


texts: Oxidation of sodium thiosulfate by iodine

texts:
When $\ce{Na2S2O3}$ reacts with $\ce{I2}$, it undergoes a redox reaction as

$$\ce{2 Na2S2O3 + I2 -> Na2S4O6 + 2 NaI}$$

Sulfur is being oxidized from a $+2$ state to a $+2.5$ state. Why isn't it getting oxidized any further, say to $3+$, to form a compound like $\ce{Na2HSO3}$?

I do notice that there's no hydrogen involved in the equation, but maybe the reaction occurs in an acidic medium?

Could someone please tell me whether the above scenario is possible or not and why?


texts: Home foundry — melting aluminum, mitigating undesirables

texts:
I am going to be melting aluminum cylinder head and some soda cans in the home foundry. I am aware the sulphur and the hydrogen present in the melt can make aluminum prone to cracks and brittle.
Are there recommended ingredients that can be put inside the molten aluminum besides flux that precipitates or remove undesirables?


texts: Sodium Silicide (NaSi) Synthesis, Reversability

texts:
I'm trying to understand a) the reaction that would produce $\ce{NaSi}$ from $\ce{Na}$ and $\ce{Si}$, as well as how to reverse the reaction of $\ce{NaSi}$ with $\ce{H2O}$. The product of the latter would be $\ce{Na2Si2O}$ (aq), and I want to understand the reaction which would transform it back to $\ce{NaSi}$ (including heat inputs).

Where could I find this information? Is there an obvious repository of chemistry information where I could look this up?

Thanks you!


texts: Why does allyl anion have only two resonance structures?

texts:
There are only two resonance structures of allyl anion with negative charge distributed over positions 1 and 3:
$$\ce{\overset{-}{C}H2-CH=CH2 <-> CH_2=CH-\overset{-}{C}H2}.$$
What's the criteria for electrons forming a double bond? Why isn't there a third resonance structure
$$\ce{\overset{+}{C}H2-\overset{-}{C}H-\overset{-}{C}H2}?$$


texts: Isomers through Nucleophillic substitution

texts:
If a single active optical isomer of 2-chlorobutane were to undergo a nucleophillic substitution reaction with iodide ions, how many optical isomers are present in the product? A mixture? Or just a single isomer?

My attempt:
Iodine can only approach the carbon atom from the opposite side of chlorine(the point at which chlorine is bonded)due to repulsion. So a single isomer is obtained as a product.

However, many of my friends are saying my logic is incorrect. Can somebody please clarify this?


texts: Find the maximum temperature attained by the gas during the change

texts:
The main question is:

  2 moles of an ideal gas is changed from its initial state $(16\ \mathrm{atm},\ 6\ \mathrm L)$ to final state $(4\ \mathrm{atm},\ 15\ \mathrm L)$ in such a way that this change can be represented by a straight line in $P{-}V$ curve. Find the maximum temperature atained by the gas during the above change. Take $R=\frac{1}{12}\ \mathrm{L\ atm\ K^{-1}\ mol^{-1}}$.

My approach :
I plotted the initial and final conditions on a $P{-}V$ curve using a Cartesian coordinate system. Joining them gives me the temperature transition.

I also made two isotherms (hyperbolic curves) on the same graph, passing through the points a previously plotted. The values of initial and final temperatures I calculated are

$$\begin{align}
T_\mathrm f&=360\ \mathrm K\\
T_\mathrm i&=576\ \mathrm K
\end{align}$$
I tried finding a function in $T$ which I could maximise, but in vain.


texts: Formation: So much heat, where does it all go?

texts:
I was comparing heat of formation numbers with specific heat values, and the numbers look really weird.

Take a typical example like magnesium fluoride. Its $\Delta H$ is -1124 kJ/mol and its heat capacity is almost certainly less than 0.1 kJ/mol K. Divide and you get at least 11000 Kelvins!

So the heat of formation doesn't seem to go into raising the temperature of the product. It can't be going into the surroundings either; otherwise the reaction would vaporize anything nearby. Where does it go, or what's wrong with my reasoning?

Edit: OK so let's not use a fluorine compound. Take aluminum nitride. -318 kJ/mol. Are we really going to suggest aluminum burns in nitrogen at over 3000 K?

Edit: Si3N4: -745 kJ/mol.

Edit: Regarding the article on adiabatic flame temperature: aluminum burns in oxygen at 4000 K. The $\Delta H$ of Al2O3 is -1680 kJ/mol. 1680/(4000-298) = 0.45 kJ/mol K. This would be a fantastic heat capacity whether we're talking constant pressure or constant volume.


texts: How To Scan "improper dihedrals" in Gaussian 09?

texts:
I am trying to parameterize Amber force field for a novel molecule, but I couldn't obtain improper dihedrals. Because if I scan impropers like dihedrals; later or sooner the molecule is overlapping and Gaussian exits with errors.
Let's say it is the $\ce{BH3}$ molecule. I tried many things for example with/without  symmetry=none keyword, with O 4 2 3 1 S 10 18.000000 or   D 4 2 3 1 S 10 18.0 (out of plane), but I couldn't get the results for a 360° improper scan.

I got this error at step 6:

 Old curvilinear step not converged, using linear step
 Error imposing constraints
 Error termination via Lnk1e in C:\G09W\l103.exe

What should I do?

Here is my gjf file:

%nprocshared=4
# opt=modredundant am1 geom=connectivity

Title Card Required

0 1
 B                  0.00000000    0.00000000    0.00000000
 H                  0.00000000    1.10873800    0.00000000
 H                  0.96019500   -0.55436900    0.00000000
 H                 -0.96019500   -0.55436900    0.00000000

 1 2 1.0 3 1.0 4 1.0
 2
 3
 4

D 4 2 3 1 S 10 18.000000


texts: Are all NO3- salts soluble in water? If so, why?

texts:
All the examples of $\ce{NO3-}$ salts are soluble in water (all that I know about).
Is it always so or there is some salt which doesn't dissolve in water?

If so what is the reason behind it?


texts: Single step transformation of a carboxylic acid into an aldehyde

texts:
What are the different ways of transforming a carboxylic acid into an aldehyde in a single step ? (as opposed as for instance first transforming it to an ester then to an aldehyde)

The bottom of this page doesn't indicate any such way.

I am not looking for a "big-list", so the most common ways would be enough.


texts:
Why does the mixture of gases $\ce{NH3}$ & $\ce{HCl}$ not obey Dalton's Law of partial pressure at room temperature?
Also, what other mixtures don't obey Dalton's Law of partial pressure


texts: Spectrometry in Chemistry & Flame Test Lab

texts:
Question 1:
You currently see two colors that are two similar (dark yellow and orange) in a flame test lab. And also you have a hard time differentiating the colors, what is an alternative to distinguish the two compounds?

My thoughts:
I thought that it was because if you use a wooden splint to dip it into the chemicals, you accidentally combust it causing the inaccuracy and also the source of the flame is blue making it hard to see, thus you use a metal wire and dip that and put it just so slightly on top of the flame to not mix the blue color of the butane flame and the flame that came with the chemicals on the wire. Also to use a digital spectrometer for more accuracy

Am i right about my answer?

Question2:
Let's say that you are using reusable metal loops instead of wooden splints, and you were doing two flame tests of the same chemical and you get different colors, what is the error and the reason?

My thoughts:
I was really confused, maybe because for one of them you placed it too far from the flame source and for the other you placed it too close to the flame source?


texts: Why is the pKa of a ketone higher than of water?

texts:
The pKa of water is 16, while the pKa of a ketone, HC3(CO)CH3, is closer to 20.
The lower the pKa the stronger the acid. When a ketone loses a hydrogen, the NBE are resonance stabilized into the carbonyl group, lowering their energy, increasing the acidity. When a proton is removed from water, the NBE have no resonance structures. Yet it has a lower pKa, so it is a stronger acid.

Why is this?


texts:
In chemical kinetics , we learn that in a reversible reaction ,both the forward reaction and reverse reaction occur at the same time. At equilibrium , the rates are the same. For example:Production of ammonia NH3 .During the production of ammonia both the forward & reverse reaction is present .

$\ce{ 3H_2(g) + N_2(g) ⟶ 2NH_3(g)}$ forward reaction

$\ce{2NH_3(g) ⟶ 3H_2(g) + N_2(g)}$ reverse reaction

Now come to the Gibbs free energy.

Under standard condition(298K) , it can be calculated that the reaction is forwardly favored (forward reaction is spontaneous,and thus the decomposition of NH3 is non-spontaneous).
I understand H2 and N2 will produce more NH3.My question is at this situation will NH3 decompose into H2 and N2 to some extent(though it is a non-spontaneous process)?.But chemical kinetics tells that both reaction(not necessarily same rate) have to be present to create equilibrium in future .


texts: The number of optical isomers of 3,4-dichlorobutan-2-ol

texts:
The number of optical isomers possible for the given organic molecule is?
$\ce{CH_3-C^*H(OH)-CHCl-CH_2Cl}$ (the configuration is fixed at $\ce{C^*}$)

The given answer is 2.
The carbon marked with an asterisk is chiral, and the carbon to the right of it is also chiral. Doesn't that give 4 isomers? What does "configuration is fixed" mean?


texts: This is probably really obvious, but I really don't understand. Why does oxygen dissolve in water when oxygen is a nonpolar molecule and water is a polar molecule? It's obvious that oxygen does dissolve, or else fish could not survive, but I'm confused on how it does so.


texts: Is there a way to form only ortho product without using fractional distillation?

texts:
Using benzene and ethane as your only source of carbon in the final molecule, synthesize the following using any useful reagents. Reaction must form pure ortho compound.

I have to form the product shown in the picture with only the ortho position formed. I'm not sure how to do this other than with fractional distillation, but I doubt that's what my professor is expecting from me, so there must be another way I am not thinking of.


texts: What happens to air at 1000 degrees Celsius

texts:
I was looking at the graphs for the density of air at different temperatures (link below) and I was wondering if air would not react with itself at high temperatures? I read that oxygen and nitrogen react at 1600 degrees Celsius, but even below that average temperature (because of the Maxwell Boltzmann distribution) I’m guessing the reaction takes place? Also would it just catch fire with contact with anything in the environment like carbon / almost anything? I’m wondering about the hypothetical use in hot air balloons with very high temperatures and low volumes.

https://www.engineeringtoolbox.com/air-density-specific-weight-d_600.html


texts: What's the mechanism of the following reaction? Seems like internal attack occurs, but would be great if someone could provide a step by step mechanism.


texts: How does electrophilic bromination with 1,2-dibromoethane work?

texts:
Hi I am trying to figure out the mechanism of a reaction containing a lithium carbanion and 1,2-dibromoethane in THF. The lithium carbanion is generated by deprotonating using LDA. Then 1,2-dibromoethane is added to get the desired product (see image)

I think that the carbanion is brominated, otherwise this reaction does not make sense, but I really don't understand the mechanism. 1,2-dibromoethane can undergo a reductive elimination of the bromide-ions to form bromine and ethene. But in this specific reaction, I have no reductive agent... So how does the carbanion get brominated? Is it simply a fragmentation reaction, where the carbanion attacks the Br of 1,2-dibromoethane?

These are my thoughts on the intermediates.

Thank you!


texts: How do you neutralize pH of a solution by not knowing concentration

texts:
If I had a pH 10 in a 100ml solution of water and 93% sodium hydroxide how much mg/l of 93% sulfuric acid would we need to use to reach a pH of 4.

From my dated college chem books and a lot of google searching i know

1.) One mole of sulfuric acid will neutralize two moles of sodium hydroxide, as follows:

$$\ce{2NaOH + H2SO4 → Na2SO4 + 2H2O}$$  (the result is two water and one salt)

2.) 1 Gallon = 3785.41 mL or 378.541 L

3.) pH + POH = 14

4.) In one minutes time we will have 100 gallons or 378541ml (100 gallons * 3785.41 = 378541 mL)

5.) pH = 10 (of our water/sodium hydroxide solution.)

6.) The hydronium ion concentration can be found from the pH by the reverse of the mathematical operation employed to find the pH.

 10^(-pH) = hydronium ion concentration

 hydronium ion concentration = 10^-10 = 1e-10 M or 0.0000000001 mol/l

 378.541 L * 0.0000000001 mol/l = 3.78541e-8 moles

 we need a hydronium ion concentration of 10^-4 which is 0.0001 mol/l

How do i put this all together?


texts: pH responsive polymer which is immiscible in water?

texts:
Can anyone suggest a pH-responsive polymer, which is immiscible in water (polar solvent) but miscible in oil (e.g vegetable oil)?

I want to study the change in the density of such polymers when they are subjected to changing pH.

Edit:

I'm having a biphasic system of oil & water, and want to study the viscosity changes of oil with time!

For this, I was earlier thinking of having a polymer in the oil phase itself and somehow triggering (changing) its state of polymerization (density) by changing the pH of the underlying aqueous solution! (remember it's a biphasic system of oil & water).

But after reading some more papers and getting help from the underlying comments, I think it's not possible to have a polymer in an aprotic phase and then be able to study its response towards changing pH!

So now I have thought to change the experiment to synthesis a polymer at the biphasic boundary (surface) of the water and oil phase. This polymer must be soluble in the oil phase! Hence the product of interfacial polymerization must diffuse into the oil phase.


texts:
If I had a beaker of water (i.e. many molecules), at exactly 0 °C and at atmospheric pressure, what phase would be encountered?
And would the answer to this also apply to other substances at their freezing/melting point, and out of interest, would the same effect be observed at their other "phase intercepts" too?


texts: Concept of "non-superimposable mirror image" in chirality

texts: I didn't understand the fact that chiral objects are non-superimposable on their mirror images. I mean, if you put your right hand (apparently an achiral object) in front of a mirror, the mirror image will be like your left hand, but, when you make your hand touch the mirror, isn't it superimposable on its mirror image (and hence achiral)? Doesn't that mean that everything is achiral?


texts: Why can't we find the exact position and velocity of a particle? And why is it that if the uncertainty in position is very, very large then the velocity can be determined, and vice versa? Please explain to me.


texts: Is it always the sign of the Laplacian of the electron density a good criterion to decide on the covalent nature of a bond?


texts: Why is the deprotonated form of dopamine more reactive than the protonated/neutral form of dopamine?

texts:
See this (from the Wikipedia article on dopamine):

  Dopamine, like most amines, is an organic base. At neutral or acidic
  pH levels it is generally protonated. The protonated form is highly
  water-soluble and relatively stable, though it is capable of oxidizing
  if exposed to oxygen or other oxidants. At basic pH levels, dopamine
  becomes deprotonated. In this free base form it is less soluble and
  also highly reactive and easily oxidized

I'm very curious about this since I'm curious about dopamine auto-oxidation, as it is often a cause of neurodegeneration observed in those who take amphetamines (and seems more likely in the cytosol, than the vesicles it would otherwise be in). Though I'm also curious how much auto-oxidation would happen for extracellular dopamine as well.


texts: What is the best way to remove/break carbon carbon bonds?

texts:
I am working on synthesis homework and I can not figure out how to remove a carbon substituent from a cyclohexane.

What is the best way to remove the three carbons and exchange them for a ketone?


texts: De-/protonation of R-OH group by acids and bases

texts:
Let $\ce{R-OH}$ be a group with a $pK_a$ of 16. Are the following two statements correct?

In principle, the group can protonate another acid with $pK_a > 16$, and so (put differently), any "acid" with $pK_a > 16$ can be used to "deprotonate" the group
If I had a table with bases were only $pK_b$ values were given, in order to select these bases from the table which are able to deprotonate the group, I would need to choose the bases with $pK_b < -2$ because the $pK_a$ values of their conjugate acids (i.e. $pK_{a\text{H}}$) will be 16 or higher.


texts: Comparison between bond length of platinum and titanium oxides

texts:
This question comes from a problem sheet I recently had.
It concerns the fact that Pt-O bond lengths are typically longer than Ti-O ones, even though the radii of the two metals are similar.
My rationale is that as Ti d-orbitals are more contracted than the ones of Pt, it would form shorter bonds for that reason. I was wondering whether there is something else to it.


texts: Sodium cyanoborohydride and iminium reductions

texts:
I understand that the LAH will reduce the nitrile into a primary amine. The addition of acid will likely destroy the acetal mask and leave us with ethylene glycol and a molecule with both a ketone and an amine functional group.

However, what does the sodium cyanoborohydride do here with the acid and heat? I'm again thinking this is a red herring; $\ce{NaBH3CN}$ only reduces iminium ions as far as we are concerned... and we have an amine. Amines don't exist in equilibrium with imines.


texts: Voltaic cell: why does the rate of rusting increase when NaCl is added?

texts: There is a beaker in which there are two iron electrodes (there is no salt bridge between two beakers-there's just one beaker) and one iron electrode is being bubbled with a supply of oxygen from a pipe (causing it to rust and fall to the bottom of the beaker). There is a flow of current in an external circuit (which I think is because the oxygen prevents one electrode from dissociating into $\ce{Fe^2+}$ and $\ce{2e-}$). The one that is not being bubbled with oxygen is the anode, but I'm not sure why. I think it's because the other one can't dissociate since it's reacting with oxygen. Also, the rate of rusting increases when $\ce{NaCl}$ is added to the water. Why is that?


texts: how to use di-tert-butyl dicarbonate (diBOc) as a solvent?

texts:
how should we use di-tert-butyl dicarbonate(diBOc) as solvent?

In reference, diBOc was in the form of a liquid but when I checked the bottle it was in solid state.
diBOc should be stored at 8-10 ℃. So how is it possible for it to be used as liquid?
Is it OK to melt it at RT? Wouldn't melting, make diBOc have structural differences?


texts: How to find the standard enthalpy and entropy for the dissolution of silver chloride?

texts:
A maximum of $1.89~\mathrm{mg}$ of $\ce{AgCl}$ will dissolve in $1.00~\mathrm{L}$ of solution at $25.00~^\circ\mathrm{C}$.  A maximum of $5.26~\mathrm{mg}$ of $\ce{AgCl}$ will dissolve in $1.00~\mathrm{L}$ of solution at $50.00~^\circ\mathrm{C}$.  Use this information to calculate $\Delta H^\circ$ and $\Delta S^\circ$ for the following reaction.
  $$\ce{AgCl~(s) -> Ag+ (aq)~+ Cl- ~(aq)}$$
  Assume that ΔH and ΔS are independent of temperature.

I started off by converting the given masses into moles using molar mass of $\ce{AgCl}$ and since we're given the reaction, we can assume that $K_\mathrm{sp}=[\ce{Ag+}][\ce{Cl-}]$, thus

At $25~^\circ\mathrm{C}$, after doing conversion I got $1.32\cdot 10^{-5}~\mathrm{mol}$ of $\ce{AgCl}$
At $50~^\circ\mathrm{C}$ I got $3.67\cdot 10^{-5}~\mathrm{mol}$ $\ce{AgCl}$

Since, $K_\mathrm{sp}=[\ce{Ag+}][\ce{Cl-}]$ and mole ratio is 1:1, I calculated the two $K_\mathrm{sp}$ values:

At $25~^\circ\mathrm{C}$: $K_\mathrm{sp1} = 1.74 \cdot 10^{-10}$
At $50~^\circ\mathrm{C}$: $K_\mathrm{sp2}= 1.35\cdot 10^{-9}$

Now, we do have two temperatures and two equilibrium constants which empowers me to use this formula:
$$\ln\left(\frac{K_1}{K_2}\right)=-\frac{\Delta H}{R}\cdot \frac{T_2-T_1}{T_1T_2}$$

After solving for $H^\circ$  I get $65.6~\mathrm{kJ/mol}$ which is the correct answer.

How do I find $\Delta S$? I tried calculating it via standard $$\Delta G= \Delta H - T\Delta S$$ and averaging but it does not work.


texts: How do I interpret a flux quoted in cm⁻² s⁻¹ in atmospheric chemistry?

texts:
I'm reading a paper about the atmospheric chemistry on Titan {1}. It quotes "column photochemical and loss rates" for various species in units of  $\mathrm{cm^{-2}s^{-1}}$. These figures are the overall rates at which these species are generated photochemically according to a model, and I would like to convert them into units of $\mathrm{mol/s}$ or $\mathrm{mol/s/m^2}$.

However, I don't know how to interpret the given units of $\mathrm{cm^{-2}s^{-1}}$. It feels like it should be something like CCs of gas produced per $\mathrm{cm}^2$ of the planet's surface area - but that would be $\mathrm{cm\,s^{-1}}$ rather than $\mathrm{cm^{-2}s^{-1}}$. No matter how I look at it I can't see where the $\mathrm{cm^{-2}}$ comes from - is anyone able to explain this?

{1} P. P. Lavvas et al. (2008) Planetary and Space Science 56, pp. 67-99.


texts: Pressure vs electric conductivity in solids

texts: If we apply pressure to a solid, does it change its electric conductivity? I am asking this because in 2020 they announced a superconductor at room temperature but under a pressure of 3/4 of the pressure in the core of the Earth. Decreasing pressure decreased the critical temperature. So I was wondering if pressure affects the electric conductivity of other materials as well? And if it does is there an intuitive explanation, why?


texts: Will lead bind to dissolved polymer (Kapton) monomers?

texts:
We are attempting to determine the concentration of lead impurities in Kapton. Essentially we need to extract lead in the tape polymer Kapton (structure seen below);

The amount of lead in the tape is expected to be extremely low.  I plan on dissolving the Kapton into its monomers using a mixture of NaOH and hydrazine(N2H4). The process of then extracting lead ions from solution is figured out. However, I have to be sure that approximately 100% of the lead which is in the Kapton is dissolved in solution and not bonded to the Kapton monomers.

Will the oxygens on the monomers bond with any lead ions and therefore inhibiting any further reaction with that lead atom? If so is there a way to separate the lead atoms from the Kapton monomers?

Since we actually add lead separately as we are looking at the isotopic ratio, another solution to this issue would be if the lead binds to the Kapton only rapidly and is then replaced with another lead atom. This would mean that the ratio of added lead and lead impurity are equal in the solution as well and in the Kapton monomers. Is this a valid assumption over a certain time period?

Any comments would be helpful. Thank you.


texts: Can entropy in a closed system remain constant when you heat a liquid?

texts:
This is in regards to an exam question that I did not understand and got wrong.

The question was: When you heat acetone from 200 K to 400 K, what happens to the entropy?
Answers: Increases, decreases, more info needed

I put more info needed, but this was incorrect. My logic was that if you have a sealed container completely filled with acetone (there is no gas or empty space in the container) and you heat it, there are no new states that the liquid particles can occupy so there is no change in entropy. Is this reasoning incorrect?


texts: Alternative mechanism for carbocation rearrangements

texts:
Is there no alternative mechanism for carbocation rearrangements rather than hydride shifts? I've been killing myself over this thing for over two days, and I do believe that hydride/alkyl shifts are not only unfavourable, but unnecessary as well.

What follows might be a little weird to comprehend at the first try, but please, stay with me here...

Let us deal with one of the simplest situations we can think of, say, 1-butanol in acidic medium.

The H+ ion will interact with the lone pair in oxygen and H2O goes out. Till here we are all in the same boat. Now comes the interesting part.

We're all familiar with the classical theory, so I shall not waste time discussing that mechanism (kindly refer to the enclosed series -1 if in doubt).

I shall only point out what seems, to me, a major flaw.

When the primary carbocation is formed, it causes a number of things to happen:

(1) The electronegativity of the carbon holding the positive charge increases drastically.

(2) This increase in electronegativity causes a dissatisfaction in the adjacent carbon, increasing, in turn, the second carbon's electronegativity significantly.

As it is, carbon has a higher electronegativity than hydrogen. now, you've gone and increased it even further. Now, when the carbon(2)-hydrogen bond is cleaved, what would one expect? One would expect that the electron pair is retained by the carbon and hydrogen goes out as H+. The classical theory suggests that the opposite of this is true. How, then is that kind of bond cleavage feasible?

I say that it is not. It is my strong conviction that nature, in fact, doesn't work that way. Let us look at an alternative mechanism to this kind of a reaction.

(I request all of you to kindly assist me in finding the flaws in what I shall put forth now, for if I can think of it, so can every other person on the planet, and it is impossible that some organic chemist didn't think of it before me. Since it has not been accepted, there HAS to be a flaw. What I think has been expressed in the enclosed Series-2.)

According to the alternate theory, the carbon(2)-hydrogen bond is cleaved as one would expect it to. A comparatively stable intermediate, namely 1-butene, is formed.

There is a comparatively higher electron density in the region of the pi bond. Hence, in absence of any other option, the proton stays in the vicinity of this pi bond, due to electrostatic force of attraction.

This system, when given enough energy(via collisions with other molecules), cleaves the pi bond and the electron pair, now retained by one of the carbons   (most of the time with carbon(1) since a primary carbanion is much more stable than a secondary carbanion), is given to H+, thus giving you your desired secondary carbocation.

After the formation of the secondary carbocation, the formation of 1-butene/ 2-butene is but a trivial question, which happens in the same way as what the classical theory suggests.

So... Is there any other theory as well? Is what I propose feasible? We can never know the absolute truth, of course, but how close are we to it?

PostScript: I am very much aware that what I state is not something new. It must have crossed many other minds before mine.


texts: DNA-Sequencing (detection of the change of pH-value) after emulsion PCR

texts:
I have troubles with understanding the exact order of the steps for DNA-sequencing after the Emulsion PCR (EmPCR). The EmPCR fills each bead with the same DNA strand (copies it $n$ times, till the bead is entirely filled up). But how is then the sequencing done with these beads?

The sequencing is described as follows (in easy words): Each nucleotide is provided to the DNA strand. If a nucleotide is accepted, the $\ce{H+}$ concentration rises and can be detected. Hence, the complementary nucleotide was present at the DNA strand.

But to be able to attach a nucleotide to the DNA, it has to be broken up. But the EmPCR already filled up every copied DNA strand. Where is it then broken up again?


texts:
The degree of dissociation of $\ce{NH3}$ at $\pu{1 atm}$ is 20 % as follows:
     $$\ce{2NH3 <=> N2 + 3H2} $$

I follow two ways but end up with two different answers.

Here, I assume that initial amount of reactant mole is 2 and that of product is 0. Then I take the amount of ammonia in equilibrium to be $2-2\alpha$, nitrogen to be $\alpha$ and hydrogen to be $3\alpha$. Then, I find $K_\mathrm{p}$ (where $\alpha=0.2$).

Here, as dissociation is 20 %, I assume that amount of ammonia in equilibrium will be 0.8 and that of nitrogen and hydrogen will be 0.2 and 0.6 respectively. Then also, I find $K_\mathrm{p}$, but it differs from the initial one.

Where am I mistaken?


texts: What happens to the structure of tetracyclines when they expire?

texts:
I need to explain (chemically) why expired tetracyclines should not be used, relating to the changes in tetracycline structure that occur.

All I can find is that they cause nephrosis, but not why.


texts: I want to do a lab with my students in which they will try to prove how much sugar is in a can of coke. I know that distillation is the go-to method for separating out the syrupy sugar mix, but does anyone know of a method that goes further to separate out the pure granulated sugar and not just a syrup?


texts:
I was going through my chemistry textbook (Chemistry, 10th Ed. by Raymond Chang) when I encountered this explanation of lattice energy.

9.3 Lattice Energy of Ionic Compounds
We can predict which elements are likely to form ionic compounds based on ionization energy and electron affinity, but how do we evaluate the stability of on ionic compound? Ionization energy and electron affinity are defined for processes occurring in the gas phase, but at 1 atm and 25 °C all ionic compounds are solids. The solid state is a very different environment because each cation in a solid is surrounded by a specific number of anions, and vice versa. Thus, the overall stability of a solid ionic compound depends on the interactions of all these ions and not merely on the interaction of a single cation with a single anion. A quantitative measure of the stability of any ionic solid is its lattice energy, defined as the energy required to completely separate one mole of a solid ionic compound into gaseous ions (see Section 6.7).

In this text, it seems like the writer is implying that for an ion pair in the gaseous state, ionisation energy (IE) and electron affinity (EA) can be used to measure it's stability. But even an ion pair in the gaseous state is held by an electrostatic force that gives it more stability, so more energy will be needed to separate the ion pair and that energy  would be more than IE and EA. What does the writer mean, and what is the correct definition of lattice energy?


texts: Fischer's projection, enantiomers and diastereomers

texts:
Given Fischer's projections of a few stereoisomers of some compound, how can we find out if they are enantiomers, diastereomers, etc.? From what I understand, we can rotate the projections to have the same groups on the top and bottom and then compare (non-superimposable mirror images --> enantiomers, non-mirror image --> diastereomers) and we can convert to eclipsed sawhorse projections and vice-versa, could anyone explain further?
EDIT: I have a doubt in the following MCQ question from VMC's JEE archive -->
Q. Which of the following forms a pair of enantiomers?

(A) I and II
(B) III and IV
(C) I and IV
(D) I and III
The answer is given as (D), that is, I and III. I also got this as an answer, but I also got III and IV, which is (B) as enantiomers, as I and IV were identical in my solution


texts:
When you collect a gas over water, you have to account for the mixed in water vapor by subtracting the room pressure from water vapor pressure. However, why do you not do something similar for volume, where you subtract the total measured volume from the volume of water?

How can $PV = nRT$ still hold when the pressure you are using is only for the collected gas whereas the volume is for the gas + water vapor volume?


texts:
Can I boil off chlorine?
Does it evaporate quickly at high temperatures?

I am asking because I want to remove it from drinking water, and I don't want to wait 24 hours for it to evaporate naturally.


texts:
I was always confused as to how electrons where donated from the anode in a galvanic cell. But after doing research, I found that there are four fundamental ways as to where electrons in anodic transformations can come from:

1) Surface metal atoms

2) Solvent molecules

3) Electrolyte anions

4)Base ligands

My question is how do I know from these four options, which is providing the electron?


texts: Ratio of MbO2/Mb in a satured solution of dissolved oxygen from dry air

texts:
What is the ratio of $\ce{MbO2/Mb}$ if the solution is saturated with air?

  Details of the question:
  $$
\begin{align}
\ce{Mb + O2 (aq) &-> MbO2}\\
\Delta G' &= -30.3~\mathrm{kJ/mol}\\
T &= 298~\mathrm{K}\\
\ce{pH} &= 7\\
\text{Henry's Constant for }\ce{O2}  &= 42 \cdot 10^3~\mathrm{bar}\\
\text{Content of }\ce{O2}\text{ in dry air} &= 21\%\\
\end{align}
$$

Attempt at Solution:

So, basically this is a two part question, as I see it. First I need to figure out the concentration of dissolved $\ce{O2}$ using Henry's Law. Then I can simply plug this value into the $$\Delta G' = -RT\ln K$$ equation where $$K = \frac{\ce{[MbO2]}}{\ce{[O2][Mb]}}.$$

Therefore:
$$
\begin{align}
P &= K\cdot m\\
0.21~\mathrm{bar} &= (42 \cdot 10^3)\cdot m\\
m &= 5 \cdot 10^{-6} \pu{mol/kg}\\
-30.300~\mathrm{J/mol} &= -8.314 \cdot 298 \cdot \ln\left(\frac{\ce{[MbO2]}}{[5\cdot10^{-6}]\ce{[Mb]}}\right)
\end{align}
$$
After dividing and raising both sides to $e^x$ (to get rid of $\ln$) I get $$\frac{\ce{MbO2}}{\ce{Mb}} = 1.02.$$

However the answer sheet says it is $21.6$. I cannot figure out why this is so.


texts: Elucidating reaction mechanism and purpose

texts:
Please help me understand synthesis sequence shown below:

Benzylbromide is used for protection, probably from action of $\ce{CuBr2}$, but it's reaction mechanism is unknown for me. The bromination of the methyl group is some kind of radical reaction? What would it do to the rest of the molecule weren't it for benzylbromide? Next, 18-crown-6 is clearly used as catalyst for halogen exchange — but how does it function? Does it enclose bromine making $\ce{Br-}$ a better leaving group or $\ce{F-}$ better nucleophile? Finally, how does $\ce{CF3COOH}$ manage to remove that protecting group? Maybe it protonate benzilic $\ce{O}$ leaving the stabilized carbocation behind? But this seems quite unlikely since this would probably attacked fluorine or carbonyl.


texts: What is the bonding picture in Peroxomonosulfate?

texts:
In $\ce{SO5^{2-}}$, can somebody tell me which orbitals are used to form the pi bonds in this anion.
Please tell the hybridization.
And the lewis structure.

Well I tried and the answers I got was sp3 & the pi bonds are formed using d orbitals.I just need to know whether I'm correct


texts: What happens to gasoline when it lands on your hand?

texts:
I was filling the mower with gasoline and some gas splashed on my hand. Not even 2 seconds later it was gone...

1) Does gasoline turn into vapor that fast? And if it does, why doesn't it evaporate in the gasoline can?

or

2) Does it seep into your skin and into your blood?

Also.. after it had 'dried' there was a white residue leftover, what is it?


texts:
A sample of hydrogen at a pressure of 7.10×10-2 atm and a temperature of 26.4 K is compressed at constant temperature to a pressure of 18.5

Which of the following are true?
1. One or more phase changes will occur
2. The sample is initially a solid.
3. The liquid initially present will vaporize.
4. The final state of the substance is a liquid

The sample is initially a gas

MY ANSWER:
I feel that one or more phases will change and that the liquid present will vaporize as it surpasses the supercritical point.


texts:
From someone coming from electronic engineering not skilled in chemistry,

There are transparent electric conductors in form of ITO ( Indium tin oxide ) coated glass or transparent PET films ( Polyethylene terephthalate ). By etching the ITO coating we can create transparent circuit boards and with the case of ITO coated PET also flexible transparent circuit boards.

There seems to be very little info on what can be used for etching ITO PET sheets.
For ITO coated glass, people use HCL with no issue, but will HCL also work to etch ITO but leave the transparent PET film intact, or
do PET and HCL react?


texts: Impediments to GC-MS characterization of petroleum products

texts:
In an attempt to characterize, and sometimes to 'match' oil on feathers of birds, a laboratory utilize gas chromatographic - mass spectrometry. Persons likely to encounter oiled birds are advise to NOT wrap the bird in plastic, as this may affect results of the analysis, rather to use foil for containment, transport, and of course, to avoid cross-contamination with other hydrocarbons.

Exclusive of issue and presumed effects of cross-contamination by other hydrocarbons, how significant is short-term (< 48 hour) storage of oiled bird(s) on the assessment of contaminated plumage?

Thank you if you can provide an answer to this question.


texts: Leaving group ability and solvent's effect

texts:
Regarding leaving groups and solvent effects (SN1 and SN2 reactions), I would like to ask some questions.
As the nucleophilic character is also influenced by the solvents, there is some indication (to me at least) that the leaving group can be influenced as well. Unfortunately, there is not much information found. Let us consider the halides, the quality of the leaving group is $\ce{I-} > \ce{Br-} > \ce{Cl-} > \ce{F-}$ as the larger ions are more polarizable, more stable and less basic.
So imagining a polar protic solvent, wouldn't the solvation stabilize $\ce{F-}$ via hydrogen bonds? I totally understand, that fluorine forms tighter bonds with carbons, so it naturally is a bad leaving group.
Considering the Finkelstein reaction, the driving force of the reaction is the formation of an insoluble salt, so basically the solvent influences the leaving group ability.
So, can I generally say that the solvent can theoretically influence the leaving group ability? Is there some general thumb rule I can use?
Until now, I haven't seen any reaction, where $\ce{Cl-}$ is preferred over $\ce{I-}$ as a leaving group except for the Finkelstein reaction.


texts: What's the reddish powder that oozes out of a black rock?

texts:
As an artist, some of the work I do involves the use of seashells, sea rocks/stones, etc.
I picked up a black rock from shore at one of the beaches here in Florida and it looked somewhat clumpy with other rocks and debris encrusted on it. As I do with everything I collect, I thoroughly washed all the rocks with fresh water and then placed them in a bucket filled with water and a good dose of bleach.

After drying the rocks, I noticed that the black one had small, reddish, powdery pimples all over it. It looked odd, so I broke the rock in half with a hammer,but there was nothing red inside. It actually looked like carbon, but the rock isn't brittle or powdery. I stuck the two halves back in a bucket, filled it half way with water, and them put more bleach in it. The water turned dark, almost muddy, and a reddish, almost gelatinous precipitate appeared and it was quite a bit of it. Any idea what the heck is in that rock that can cause that? I didn't notice any odor other than the bleach, albeit the rock did smell a  bit sulfury. Any idea what I have soaking in the bucket?


texts: How do you calculate the nuclear spin multiplicity of radicals such as $\ce{N2H+}$? How does the net charge on the molecular species effect its overall nuclear spin?


texts:
I know that this constant tells us the strength of the interaction between the metal and the ligand,  so should it also mean that the higher the constant, the stable the complex ?
I need to make sure of it because in photometric titration, all that matters is the stability of complex, and if the constant is given, one should know which complex is formed earlier.


texts: Pressure is the magnitude (absolute value) of the force over the area, so how can that result in a negative value for pressure as would happen in certain circumstances?


texts: Why is tin(IV) iodide bright orange while elemental iodine is violet?

texts: Does it have anything to with iodines polarizability? Is there a way to explain this using sigma bonding or an MO diagram?


texts: Thermodynamics of Acid Base Neutralisation

texts:
I was attempting an exam in which they questioned us about the thermodynamics of acid-base reaction.
The question was this:

  In neutralisation reaction of a strong acid and a strong base in a solution, the following statements are correct

and then they gave these four options

  ∆G = negative
  ∆H = negative
  ∆S = negative
  ∆U = negative

We can easily see that Option 1 and 2 are correct, but in the key, it has been specified that Option 3 as well as 4 are correct, too.
Can anyone please explain this to me.


texts: Why does Cu not react with dilute H2SO4?

texts:
$\ce{Cu + (dil) H2SO4 -> No Reaction}$

but

$\ce{Cu + (conc) H2SO4 -> CuSO4 + SO2 + H2O}$

What is the difference between the dilute and concentrated acid that one reacts but the other doesn't? They both are the same thing except that dilute one has more water than the concentrated one.


texts: Reaction between phosphorus(III) bromide and alcohol

texts: Alcohol acts as a nucleophile in a reaction with $\ce{PBr3}.$ It attacks the $\ce{PBr3}$ leaving $\ce{Br-}$ behind. The alcohol forms a bond with the $\ce{PBr2+}.$ How the oxygen having three bonds makes the hydrogen more acidic?


texts: Can molecules diffuse upstream when emptying a cup of tea?

texts:
I was drinking some tea, and I randomly decided to pour some into the toilet in an unbroken stream; can particles travel "upstream" quickly enough to reach the mug of tea? How fast can diffusion occur in this system?

What if I pour it into highly concentrated toxic waste?  Given that even trace amounts could make it toxic, should I not drink my tea?


texts: Most favorable position of attack of an electrophile on 4-trifluoromethyl-1,2-diphenylbenzene

texts:
Problem
This problem is from a FIITJEE AITS paper

Which position is most favorable for the attack of an electrophile?

Answer

 Position 2

My attempt
The more favorable position for attack should be the on the para ring (considering ring with $\ce{-CF3}$ group as the reference ring), because of the lower inductive effect as compared to meta position.
If the electrophile attacks at position $1$ or $6$ (which means the carbocation will be formed at the carbon connected via a double bond), the carbocation would be equally stabilized by resonance, also the charge can move to the other 2 rings forming 9 Resonating structures.
If carbocation is formed at position $6$ by the electrophilic attack on 2nd position, the carbocation won't be able to move out to other rings for resonance implying that there would be only 3 resonating structures.
So my answer would be:

 Position 1 or 6

Why is my answer is wrong? What is the correct explanation?


texts: multielectron spin-orbit coupling and energy level

texts:
For multi-electron atoms for which the Hamiltonian (including the spin-orbit coupling) reads

$$H=\sum_i T_i-Z\sum_i V_i+\sum_i V_i^{\text{s.o.}}+\sum_{i>j}V_{ij}$$

The $T_i$ are the kinetic energy of the individual electrons, $V_i$ are the nuclear Coulomb attraction, $V_i^{\text{s.o.}}$ is the spin-orbit coupling, and $V_{ij}$ are interelectron Coulomb repulsion.

In http://www.tcm.phy.cam.ac.uk/~bds10/aqp/handout_atomic.pdf (page 103), using Wigner-Eckert, they are able to diagonalize the spin-orbit in terms of the total orbital and spin angular momenta of all the electrons.

Although it says it is beyond the scope of the course, I would still like to know how to do it.  I am pretty familiar with the Wigner-Eckert theorem in its basic form (that the matrix elements of a tensor-operator can be written in terms of a C.G. coefficient times a reduced matrix element).  Thanks.


texts: Calculating the energy of a molecule using probability distributions

texts:
I wish to calculate the energy for a protein where the position of all the C-alpha atoms is known.

One way is to calculate the pairwise distances between the atoms and then look up a probability distribution to determine the likelihood that the distance for that particular pair is the given value, take the negative logarithm of that value, sum this over all pairs and this is a proxy for the molecular energy. This is the approach taken by the machine learning community. (Physics-Based Design of Protein-Ligand Binding)

Can anyone point me to a sample calculation or publication where this is elaborated in some detail?

I have very little background in chemistry beyond the introductory college courses. The question that I am trying to research is this: Given two spatial configurations of a molecule, how does one determine that one configuration has a lower energy than the other? What is the benchmark that is used for measurement? When Ramachandran generated the plots of torsion angles, how were the optimal angles calculated?


texts: What is the difference between the chemical potential μ and the molar Gibbs free energy Gm?

texts:
I'm not too sure if I understand this correctly:
Is the $G_\mathrm{m}$, the Gibbs free energy of the entire system, divided by the amount of substance making up the system, while $\mu$ is the Gibbs free energy of a component of the system?

If so, what does ${\partial G_\mathrm{m}}/{\partial n}=\mu$ signify? As in, what's the difference between this and $\mathrm{d}G/\mathrm{d}n=\mu$?


texts:
The question is to find out the final product $T$ in the following series of reactions.

I am provided the following options to choose from

With alcoholic $\ce{KOH}$ elimination will occur and with $\ce{KOH}$ syn diol will be formed in place of double bonds.I am unable to see what will $\ce{CaO}$ do to the syn diol.I had an idea that it is used for decarboxylation hence the final product should have 1 carbon less but I am unable to get the right answer.Any ideas?Thanks.


texts: If a bond dissociation energy is listed, does it refer to homolytic or heterolytic fission?

texts:
I am perfectly sure than heterolytic fission of a bond needs more energy than homolytic ones, since it requires opposite charge separation. When the bond dissociation energy is listed, which one are they talking about?

Ex: Suppose bond energy of A-B is 500kJ/mol. Is the energy to make A radical + B radical, or A cation + B anion, or A anion + B cation?


texts: Can you fix rubber on a handle after it has all but turned into a liquid?

texts:
I picked up a splitting maul at a yard sale last year. I used it for the rest of the season with no problems. It has been in the wood shed and exposed to some sun, but mostly shade.

I picked it up the other day and it stuck to my hand. When I tried to let go, it slid from my hand, leaving behind black goo and rubber from the handle. Now it's so bad the whole rubber part is gooey and if I try to rub anything on it the rubber comes off. It's permanently soft and sticky and is coming off the handle.

Can I save it or is it done?


texts: Steric Inhibition of Resonance in ortho-substituted Benzoic Acids

texts:
It is given that due to Steric Inhibition of Resonance (SIR), the acidity of ortho-substituted benzoic acid increases with respect to benzoic acid. However, I'm unable to understand the reason behind this fact.

We know that resonance stabilises a molecule and the absence of which decreases the stability. In case of ortho substituted benzoic acids, resonance is inhibited due to the loss of planarity due to the steric interactions from the ortho substituent.

If this is the case then the conjugate base of the acid will not be stabilized by resonance with the benzene ring. So it seems the ortho-substituted benzoic acid will not readily donate H+ and is less acidic than benzoic acid, contrary to what is being given in various sources.

Then kindly explain why is ortho-substituted benzoic acid is more acidic than benzoic acid.


texts: How toxic chemically is plutonium (Pu), neglecting the radioactive damage?

texts:
In Rhodes' The Making of the Atomic Bomb, he says that, while Pu is not that radioactive (which is surprising -- maybe he means compared with radium and some other elements), it is very toxic.
I would guess it could not be much more toxic than uranium (U) or lead (Pb) -- I believe thallium is more toxic than U and Pb and so is mercury (Hg). If it is more toxic than lead, do we understand the mechanism?


texts: How is it possible to increase mercury's specific weight?

texts: Is it possible to change mercury's specific weight to make it heavier? By mixing it with anything? But not by changing its temperature.


texts: how to understand to what subshell is related basis function in the Eigenvectors block (GAMESS output)?

texts:
So, each subshell of some atom is described by one or combination of few BF's. But I can't find correlation between representation of subshells in eigenvectors block and, say, basis set or something else.

How it looks:

eigenvectors block (tiny part of it), actual DFT calculation of BF2H:

                           1           2           3    ---> MO number
   atom   shell type -24.7137    -24.7137     -6.8636   ---> MO energy (a.u.)
BFs | atom num |          B2          A1          A1    ---> orbital symmetry
1   B    1     S           0      1e-006    0.496374    --->
2   B    1     S           0   -1.6e-005    0.572289    --->
3   B    1     S           0   -4.3e-005    0.097616    --->    eigen
4   B    1     S           0   -0.003145   -0.089222    --->   vectors
5   B    1     S           0    4.6e-005    0.003663    --->
6   B    1     X           0           0           0    --->

At MO 3 we can see 1s subshell of B distributed mostly on BF 1 and 2. But for another atom, shell (2s, 3s, 4s etc.), subshell type (px, py, pz, dxy etc.) the distribution is very different. I can understand there what is, but I nedd to look by my own eyes on the numbers, but for systems with 30-50 and more atoms it's totally unacceptable.

That's why I use the power of C++ to parse megabytes of eigenvectors (I'm very new to programming (5 or 6 days) and I write very silly code, but... ).

So, I'll be happy if somebody help to understand on that numbers in the output to "look" to correctly associate basis funtions with shell number (1, 2, 3...).


texts: Influence of Temperature on Biochemical Reactions

texts:
Short question

How (quantitatively speaking) does temperature influences rate of decay of proteins? I am looking for some general number/function, the influence of temperature on an average protein.

Long question

For computer modeling purposes, I am looking for some referenced quantitative measurements of the effect(s) of temperature on the dynamic of biochemical reactions. In particular, my question is:

  How does temperature influences rate of protein decay?

I am looking for a function (eventually expressing the michaelis-menten constant as a function of the temperature) that I can plug in my algorithms to incorporate the influence of various temperatures on the process I want to simulate. The model under simulation is an eukaryote such as Saccharomyces telluris (a yeast) for example living at some common range of temperature [5-35 °C]. I am not thinking to any particular protein rather I am looking for some approximative effect of temperature on the decay rate on an "average protein". I welcome any kind of expression of how temperature influences the rate of decay. Some values using the Erying equation, Van't Hoff equation or a $Q10$ (measured in some reasonable range [5°C - 35°C]) for examples would also fit my needs. I would be very surprise that there is not enough literature on the subject in order to get some average impact of temperature on protein decay rate but as a biologist (and not a biochemist) I can't wrap my head around this problem and can't find any satisfying article. Thanks for your precious help!

I am not looking for...

I am NOT looking for a theoretical explanation of how temperature influences these reactions (I have basic understanding of the importance of the activation energy as displayed on a Maxwell-Boltzman distribution and of the michaelis-menten equation). I am just looking for some empirical observations of how temperature influences proteins decay rate. I am not looking for any accurate value but only for some estimation that I can plug into my algorithms.

Update

Reading the comments I realize that my question is too broad in the sense that there might have too much variance in how different proteins respond to temperature in order to draw in general tendency. If this is so, someone willing to answer may reduce the question to transcription factor, to General Transcription Factor (GTF) or even to TFIIA.

What about this article for example? I am not really able to extract from it the info I am looking for but it might be in here.


texts:
It seems betaine HCl is often recommended for those suffering from "low stomach acid" -- which, as I understand, is having too high stomach pH for proper digestion (especially for proteolysis via pepsin). However, I have a few questions then -- though I'm not sure if my reasoning is correct here:

Understandably, one wouldn't want to drink pure or highly concentrated HCl by itself to increase stomach acid! But then, what role does the betaine play?

I'm guessing betaine HCl probably does not dissolve in water to give the same pH as just straight (or concentrated) hydrochloric acid -- since then it would seem just as dangerous as drinking plain HCl!

In that case, if it doesn't decrease the pH as much, making it safe for oral consumption, what value does it bring for "lowering stomach pH" anyway? I mean, one could just drink a little vinegar or citric acid for the same effect?

Or, perhaps, is betaine-HCl just a means of some "delayed release" of HCl to lower stomach pH without hurting the mouth and esophagus during its initial consumption? Betaine may just be a useful amphoteric here, given it's quarternary ammonium and carboxylic acid groups (although not just any amphoteric, such as water, may suffice here!)

Alternatively, could the value of betaine HCl simply be in providing a source of $\ce{Cl-}$ anions, possibly for increased pepsin activity? (I'm not sure if pepsin requires merely low pH or specifically also needs $\ce{Cl-}$ anions as well) Betaine-HCl seems to be often formulated with additional pepsin enzyme(s) as well...


texts: Why is it that only ozone absorbs UV radiation?

texts:
I know the mechanism of how ozone absorbs UV but why is it that no other molecules do this?

Is there any special reason?

PS: If I'm mistaken and there are other molecules that can absorb UV please mention them.


texts: I dissolved $\ce{[Pt(NH3)4](NO3)2}$ in water then I added small amount of $\ce{NaI}$ ($1~\mathrm{M}$) to it. Precipitation occurred. I want to know what happened?


texts: Explaining boiling using internal energy

texts:
Internal energy is summation of potential and kinetic energies of a substance

Using this interpretation of internal energy, how can I explain boiling?

Kinetic remains constant.
Potential should decrease because of an increase in average spacing.
But internal energy should increase.

Can somebody explain what flaw I am making?


texts:
Can a please explain me what is electron cloud distribution in simple words?
Electron cloud is the area around which electrons are most probably found. What is meant by electron cloud distribution?


texts: I've read that vinegar can dissolve $\ce{CaCO3}$, I know that extreme heat can decompose it, but how to dissolve $\ce{CaCO3}$ at home? I need to dissolve chalk in my home because of repairing something. Can someone help me do it without heating $\ce{CaCO3}$? Any replacement for that?


texts: How to determine which of the given redox reactions will occur?

texts:
Which one of these reactions will occur?

  $$\ce{KMnO4 -> K2O + MnO2 + O2}$$
  $$\ce{KMnO4 + HCl -> KCl + MnCl2 + Cl2 + H2O}$$
  $$\ce{KMnO4 + CO2 \longrightarrow K2CO3 + Mn2O7}$$
  $$\ce{KMnO4 + CO2 -> K2CO3 + MnO2}$$
  $$\ce{KMnO4 + SO2 -> K2SO4 + Mn2O3 + SO3}$$

And how am I supposed to know which one it is? It's not just this question, I struggle with these types of questions every time. There seem to be a lot of things to take into consideration.

I'm thinking whether it's under 3 or under 4. The oxidation numbers for the reaction 3 don't change at all. But in reaction 4, only the oxidation number of Mn changes (from +7 to +4) and the other oxidation numbers stay the same (if I'm right). So, I think reactions 1, 2 and 5 definitely happen, but I don't know about 3 and 4.


texts: Why is methyl chloride a primary alkyl halide?

texts:
In a primary (1°) halogenoalkane, the carbon which carries the halogen atom is only attached to one other alkyl group.
  Chemguide.co.uk

For $\ce{CH3Cl}$, the carbon which carries the halogen atom has no other alkyl groups attached, yet my class notes say "the alkyl halide has a primary centre". So is a primary alkyl group one with is attached to 0 or 1 other alkyl group and not just 1?


texts: Intermolecular forces between carbon dioxide and water

texts: I'm wondering which intermolecular forces will exist between carbon dioxide and water. Instinctively, I would expect there to be only dispersion forces between the 2 molecules, because carbon dioxide is non-polar due to its linear shape. However, even though carbon dioxide is non-polar, it still contains dipoles. I'm curious if its possible that these dipoles in carbon dioxide will allow it to form dipole-dipole forces (or even H-bonds) with water. Could the partially negative oxygen atomspotentially accept a H-bond from water, even if carbon dioxide is non-polar?


texts: Is it true that under certain conditions, Mg can reduce SiO2?

texts: Is it true that under certain conditions, Mg can reduce $\ce{SiO2}$ and the latter the former? What are those conditions?


texts:
Which of the two structures is more stable?

As far as I know, alkenes with a greater number of hyperconjugating structures are more stable. Hyperconjugation has a greater stabilizing effect than inductive effect. So, (d) should be more stable as it has more α-hydrogens.
But the answer given in the book is (c).
Is the answer wrong? Or am I missing something?


texts: Why doesn't a halide anion react with primary or secondary alcohols using SN2?

texts:
In the tenth edition of Organic Chemistry by Solomons and Fryhle, section 6.18A of the "Ionic Reactions" chapter, in the last paragraph, they have mentioned that:

  Use of a weakly basic anion such as a chloride ion ($\ce{Cl^-}$ ), or an acetate ion ($\ce{CH3CO2^-}$) or a weakly basic and a highly polarizable one such as $\ce{Br^-}$, $\ce{I^-}$ or $\ce{RS^-}$ increases the likelihood of substitution (SN2). (emphasis mine)

But when we react alcohols with concentrated hydrohaloic acids (is that the right term?) with alcohols, we see that the rate of reaction decreases from a tertiary to a primary alcohol, indicating that the reaction is SN1. For primary alcohols, it is shown in the textbook to proceed through (SN2) pathway. [There is no such reaction mentioned with hydrobromic or hydroiodic acid (atleast I haven't come across such a reaction)].

Elsewhere, I have read about the Lucas test, which involves reacting the alcohol with hydrochloric acid and zinc chloride, where nearly no reaction occurs with primary alcohols.

My question is, why does this reaction not occur using an SN2 pathway for secondary and primary alcohols in the Lucas test? Why is it biased towards an SN1 reaction?


texts: Difference between liquid and solid stearic acid

texts:
I had some stearic acid in solid pellet format. It is slippy and in white color. I used this to make some experiments. I recently notice that some manufacturer can supply liquid stearic acid. I checked the books. Stearic acid should be in solid form at room temperature. I was confused.
Would someone help me to understand what is the liquid form stearic acid? What is the difference with the solid form? Thanks.


texts: Calculating pH of methanoic/formic acid (HCOOH)

texts:
When calculating the pH of methanoic/formic acid (HCOOH) why do we not multiply the given molarity of the acid by 2 as there are 2 moles of H+ ions, as seen in chemical formula HCOOH?
However when it comes to calculating the pH of sulfuric acid (H₂SO₄), we do multiply the given molarity by 2 as there are 2 moles of H+ ions.


texts: Concentration of acid when titration has reached equivalence point?

texts:
I'm currently working with a lab report concerning titration. One of the tasks is to calculate the concentration of the weak acid ($\ce{HOAc}$) and the strong acid ($\ce{HCl}$) at the equivalence point during titration (through $\ce{NaOH}$).

But shouldn't the concentration of $\ce{HOAc}$ and $\ce{HCl}$ in the new solutions per definition be 0. Hasn't all acid at that point been neutralized and converted to its conjugate base at the equivalence point?


texts: Dipole moment difference between ch2f2 and ch3f

texts:
In CH3F and CH2F2  the net dipole moment increases from 1.82 to 1.97 while in all other halogen substituted carbon atoms the dipole moment decreases. In the case of CH3Cl and CH3F the chlorine substituted methyl group has greater dipole moment due to longer bond length of C-Cl compared to C-F. Then when a compound of formula CH2X2 is formed than dipole moment decreases except in the case of fluorine where it increases.
 Is there any cause to this phenomenon?


texts: What is the origin of the differences between the MO schemes of O₂ and N₂?

texts:
Here are the MO schemes of $\ce{N2}$ (left) and $\ce{O2}$ (right).

Why is the $\sigma$-MO formed by the $p$ AOs energetically above the $\pi$-MO for $\ce{N2}$ but not for $\ce{O2}$?

Can it be explained this way:
In second period elements with more than a half filled $\ce{p}$ orbitals, the energy pattern of the MOs is regular.
In second period elements with less than or half filled $\ce{p}$ orbitals, as the $\ce{s}$ and $\ce{p}$ atomic orbitals have similar energies, so the formed $\ce{\sigma_{g}}$ MO would have similar energy as $\ce{\sigma_{u}}$, but because of electron cloud repulsion it has a big increase in energy, hence it is above the $\pi$ orbitals? And this phenomenom is known as sp mixing.

Or am I wrong somewhere? Is my reasoning corret?


texts: I use an ultrasonic bath in my lab for some chemical treatment of samples. It usually takes several hours with short breaks or even without it. I have a timer at the bath with a limit 90 min. So I have to run it every time again after it ends. My colleague told me that if I'm not giving a rest to the bath after every 90 min run, then the ultrasonic generator will be broken very soon. So, in general, how much time should be between the runs? Can external chilling enhance the safe treatment duration? It is a 3 liter, 100 W, 40 kHz Finnsonic bath with a heater.


texts: Why does (3E)-3,4-dimethylhex-3-ene yield a meso dihalide when reacted with Br2/CCl4 at room temperature?

texts:
The answer is B. But why? What makes it so different than the others?
I know that it attacks from the back (anti addition). But can't it do that for all and result in a meso compound?


texts: Energy required to break salt bridges in peptides and proteins

texts:
Is there a way to calculate the energy required to break a salt bridge in a peptide or on the exposed surface of a protein in aqueous solution?  Is there any useful literature on this topic?  I'm looking to disrupt salt bridge interactions, and was wondering whether it would be feasible to do this by heating the sample, or whether infeasibly high temperatures would be required!

Thanks in advance for the help!


texts: Contribution of vibrational degrees of freedom

texts:
The ratio $\displaystyle\frac{C_p}{C_v}$ for linear triatomic molecules including vibration contribution is given by: ?

Attempt:

We are aware that $C_v = \frac{fR}{2}$ and $C_p = C_v+ R$

Hence, $\gamma = 1 + \frac 2f$

Now, for $f$ we have:

$2$ rotational degrees of freedom
$3$ translational degrees of freedom
$3N - 5 = 3\times 3-5 = 4$ vibrational degrees of freedom (formula available here)

Thus, $f = 2+3+4 = 9$

And $\gamma = 1+ \frac 29  = 1.22$

But answer given is $\gamma = 1.154$

Someone in chat room told me that each degree of freedom of vibrational actually has two times contribution so we would have $2\times 4  = 8$ vibrational degres of freedom and a total of $f = 13$, which gives $\gamma = 1.154$. However then I see a contradiction here. If vibrational indeed contributed $2$ per degree then degree of freedom of methane would be $3+3+2\times(3\times 5-6) = 24$ not $3+3+ (3\times 5 - 6) = 15$.

Can someone please clear the confusion here?


texts: What reaction will ensue when sulfur trioxide is added to excess barium hydroxide solution?

texts:
Question:

If $\ce{SO3}$ was added to an excess solution of $\ce{Ba(OH)2}$, what would be the resulting reaction?

Thoughts:
Initially, I suppose it would form barium hydrogen sulfate, which slowly precipitates barium sulfate in water as the hydroxide is present in excess.
$$\ce{2SO3 + Ba(OH)2 <=> Ba(HSO4)2 \\ Ba(HSO4)2 + Ba(OH)2 <=> 2BaSO4 + 2H2O}$$
Is this correct?


texts:
Consider the reaction

$\ce{NH3 + H2O -> NH4+ + OH-}$

Here, $\ce{NH3}$ is a weak base, and thus $\ce{H2O}$ becomes a weak acid. Thus, shouldn't its conjugate be a strong acid? However, $\ce{NH4+}$ is a weak acid, instead of the strong conjugate acid it should be. Why is this?


texts: What intrinsic property do metals have that causes their delocalisation?

texts: So I understand that electrons in metals delocalise completely and are free to move around. But my question is, why would something like Nitrogen not delocalise, whereas say Iron or Bismuth does? What is special about their orbital configuration that causes this?


texts: Mechanism of Grignard addition to carbonyls

texts:
So from the general reaction we can see that the carbonyl is reduced while the Grignard is oxidized to an alkene.

So for this hypothetical reaction (does this really occur?) we are asked to provide a plausible mechanism. This is what I got, but the prof. wants something better - why transfer negative charge from oxygen to an $\text{sp}^3$ carbon?

Click on the image to enlarge, if you wish.

Here are his hints:

  Remember, prior to Grignard reaction the $\ce{Mg}$ center swaps out an ether
  solvent molecule for a reactant oxygen.  This interaction will lead to
  the reaction but in this case, due to steric interference a hydride is
  delivered instead as the Grignard is oxidized to an alkene.  In this
  way the Grignard reagent is almost reacting in the way $\ce{NaBH4}$ would in
  the presence of this ketone. Try to get all of this action working
  together in a single, concerted step.

So ... I get the first part just fine. The $\ce{Mg}$ center has an octet; it's solvated by two ether molecules in solution usually. Okay and in this case the carbonyl oxygen helps solvate the $\ce{Mg}$ center. And then hydride transfer occurs ... but how exactly do we get the hydride to leave without creating a carboanion? And is it really that important that everything be concerted?

This is my second attempt ... if this is all concerted in real life then I must have hit the orbital alignment lottery! All the stars must have been aligned ... !

The only thing I see about my second attempt is that in the end the $\ce{Mg}$ center doesn't have a complete octet - perhaps I should have shown another ether molecule popping in to help $\ce{Mg}$ out with its octet fantasies.


texts: Changes in pH when adding substances other than acids or bases

texts:
If I start out with 100 mM acetic acid, what substance (to a final concentration of 1 M) could I add to change the pH considerably? I was thinking of NaCl or ethanol or acetone. Substances added should not be acids or bases, i.e. a 1 M solution of them should have a pH close to neutral. I'm asking because I am trying to create a demonstration on how pH calculations are just approximations under non-ideal conditions.

The acetic acid should not undergo an chemical reaction (other than acid/base). I would use a pH meter to monitor the pH. I would have a control where I increase the volume to match the experiment where I add a substance that influences the pH (or dissolve the substance in 100 mM acetic acid to keep the acetic acid concentration constant).

I am looking for changes in pH based on non-ideal behavior. The concentration of acetic acid should remain the same, and there should not be any neutralization reaction. In other words, the calculate pH should stay at 2.87 (assuming ideal conditions) while the measured pH would change.


texts: Why is the test for sodium as dihydrogen antimonate so specific?

texts:
I have been attending lectures of salt analysis in my college. We are at group 6 cations or also known as group zero cations, namely $\ce{NH4^+}$, $\ce{K^+}$, $\ce{Na^+}$, $\ce{Mg^2+}$.
The lecturer wrote an equation:
$$\ce{NaCl + KH2SbO4 -> NaH2SbO4 (s) v  + KCl}$$
Now, I know that the electrochemical series follows the order $\ce{Li}$, $\ce{K}$, $\ce{Ba}$, $\ce{Sr}$, $\ce{Ca}$, $\ce{Na}$, $\dots$.
I would like to know why this reaction occurs so spontaneously that it is included as one of the lab tests. Sodium chloride is completely neutral whereas potassium dihydrogen antimonate is basic.


texts: What should be the molarity of HCl and H2SO4 acid so that they can be considered safe to touch?

texts:
I know $\ce{HCl}$ and $\ce{H2SO4}$ acid of concentration 17 M is dangerous and corrosive, but I wonder can we dilute these acids to the extent that they become safe to touch?

If yes, then what should be the molarity of that safe acid?


texts: Reactions that occur at the anode electrode of electrolysis dilute H2SO4

texts:
How to know that reaction that occur at the anode electrode is $\ce{2H2O -> 4H+ + O2}$?

Why the reaction is not the oxidation of  $\ce{SO4^{2-}}$?

This problem does not give the E0 of $\ce{SO4^{2-}}$ too.


texts: Here nitrogen can donate three electrons as it has p orbitals with three unpaired electrons. Now it is filled by electrons of hydrogen and everything is paired. It has 2 paired electrons in an s orbital. Now $\ce{H+}$ is coming and getting electron from nitrogen. How can it get from the inner s orbital?


texts: At almost 300°C, $\ce{CaF2}$ reacts with sulfuric acid and this reaction produces $\ce{HF}$. Is there any way to make a relatively dilute (10-20%) hydrofluoric acid with $\ce{CaF2}$ as the source of fluoride ions without that much amount of heat?


texts: Fluorescence quenching by palladium(II) vs. platinum(II) complexes

texts: Why do we observe much stronger (in most cases complete) fluorescence quenching by $\ce{Pd^2+}$ than $\ce{Pt^2+}?$ I work with complexes of both metals and there is no real 100% explanation I can find why this is the case. I am looking for a full quantum mechanical explanation (if possible). If you know a piece of literature, please point me towards that.


texts: Determining the reaction order of acetylsalicylic acid to salicylic acid with a spectrophotometer

texts:
How can I determine the reaction order of the reaction acetylsalicylic acid + water to salicylic acid + acetic acid with use of a spectrophotometer?

I thought of measuring the absorbance spectrum of both substances individually, compare the 2 spectra, and then look at which wavelength the absorbance of acetylsalicylic acid exists whereas the absorbance of salicylic acid at that wavelength is negligible.

Lastly, use that wavelength to calculate concentrations of acetylsalicylic acid at certain time intervals and conclude the reaction order out of the change in concentration vs time. (for example making a graph on Excel for Concentration vs time -> linear = 0 order, exponential = 1st order)

Is this possible or am I thinking too hard/easy? Is there any other other way?


texts:
What happens to 1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane when it is hydrolyzed under acidic conditions?

I know that under acidic conditions the first thing to likely happen is protonation. Does it matter which oxygen is protonated first?

Once that oxygen has been protonated it is going to want to return to neutrality.

Now we have our carbonyl restored (sort of). However, we still want to return to neutrality. Water can attack.

Then we deprotonated the attached water and regenerate the acid-catalyst and we have our original starting compound.

Is this the correct mechanism and is the product correct?


texts: Effective Bohr Radius in Transition Metal Complexes?

texts:
I am playing around with a toy model of a transition metal complex where the HOMO are $d$-electron states of predominantly transition metal character. Let's say this is a $d^1$ (or $d^9$) system and the states are split in energy by ligand field effects. The relevant HOMO orbital is some linear combination of $d$-orbitals that correctly respects the symmetry of the transition metal complex.
I want to estimate the transition probability for a quadrupole $d$-to-$d$ transition from HOMO state. In other words, calculate $\langle f\vert r_i r_j \vert i \rangle$, where $\vert i \rangle$ and $\vert f \rangle$ are some $d$-orbitals I care about.
I can roughly estimate this transition amplitude by just using the Hydrogen $d$-orbital wavefunctions with an effective Bohr radius $a_{eff}$. My question is: what effective Bohr radius should I use?
For example, Copper is said to have a 3d-orbital radius of $\sim 0.6$ Angstrom (which is not the same as $a_{eff}$ I believe), but using the Slater estimate of the effective nuclear charge, I would guess $a_{eff} \approx a_0/Z_{eff} = a_0/13.2 \approx0.04$ Angstrom.
What effective Bohr radius should I actually use for very weakly hybridized transition metal orbitals?


texts: Is it possible to extract mass concentration from DLS measurement?

texts:
DLS (dynamic light scattering) gives the particle size distribution (number percent vs. size) of particles in suspension. It also gives the count rate (cps, counts per second).

Knowing this and the physical properties of the dispersing medium and particles, is it possible to extract the mass concentration of the particles?


texts: How does the state of iodine affect its HOMO–LUMO gap?

texts:
My teacher told me that the HOMO–LUMO gap in solid iodine is smaller than that in gaseous iodine.

When I asked about the reason, he told me that it is due to higher interactions in solid iodine as compared to gaseous iodine, which I did not understand. How can the physical state of a compound affect the HOMO–LUMO gap, even though the chemical formula is the same?


texts: Can nonpolar molecules exhibit dipole-dipole forces?

texts:
Dipole-dipole forces occur when the positive part of a polar molecule is attracted to the negative part of a polar molecule. In a nonpolar molecule, there may still be polar bonds, it's just that the dipoles cancel each other out. So why can't there be dipole-dipole forces between nonpolar molecules with polar bonds? There are still positive and negative parts of the molecule, so there can be attractions between them.

For example, in $\ce{CO2}$, there are negative areas near the oxygens and positive areas near the carbon.


texts: Entropy changes during transfer of heat between two bodies

texts:
Consider two metal blocks, one at 500K and another at 300K, they are bought to contact with each other until they reach a common temperature.
Find the entropy change of each object and the total change considering there is no change in the volume of the metal blocks in the process and no the other interactions excluding the heat transfer between the two blocks.Also is this process irreversible, why?

also
$C_v= 10 J/K$ for both the metal blocks

My attempt:
This process is irreversible, as once it reaches the equilibrium temperature it cannot go back to the initial state without external intervention that is to say heat wont flow from cold body to hot body and also when two bodies are at the same temperature heat doesn't flow from one to the other to increase the temperature of one and to decrease the other.

now to compute the $\Delta S$ we can perform the same process very very slowly such that the two systems are always at equilibrium.
thus we can write $dS=\frac{\delta q_{rev}}{T}=\frac{dq}{T}=\frac{C_vdT}{T}$
thus for system 1: $\Delta S_1=C_v ln\frac{T_f}{T_i}$
and thus $\Delta S_{TOTAL}=C_v ln\frac{T_{f}}{T_{i1}}+C_v ln\frac{T_{f}}{T_{i2}}$

My questions :
I have a feeling my reasoning is not rigorous enough and my definitions are going in circles .
and my analytic solution is wrong as the i'm basically using $\delta q$ of the irreversible process and using the same information in the assumed reversible process.


texts: Why is there syn-addition in this bromination of an alkene?

texts:
In my book I read that halogenation of alkenes results in anti-addition. Is this example showing syn-addition?

The example:


texts: In density functional theory (DFT) there is classic Coulomb energy and non-classic correlation energy. But what is difference between them? In books these energies are explained very similarly. Both contributions are explained by the fact that electrons are negatively charged particles.


texts: Difference in properties of water as ligand vs 'in lattice'

texts:
I'm trying to understand the difference in properties between water in crystals in different positions in the lattice. In this wikipedia article It quotes:

  Both notations can be combined as for example in copper(II) sulfate: $\ce{[Cu(H_2O)_4]SO_4 · H_2O}$

referring to water which is coordinately bonded to the copper and water which is in the crystal structure left over.

Firstly, is this the same as:
$\ce{CuSO_4 · 5H_2O}$ ?

And secondly, would there be a difference in how the water acted upon heating? Would it only be the one water in the lattice structure that left or all 5 waters?
i.e.

$$\ce{[Cu(H_2O)_4]SO_4 · H_2O ->[heat] [Cu(H_2O)_4]SO_4 + H_2O}$$

or

$$\ce{[Cu(H_2O)_4]SO_4 · H_2O ->[heat] CuSO_4 + 5H_2O}$$