texts:
Saturated fat molecules have no double-bonded carbons, so they are long and straight, which means they stack easier and tend to form solids at room temperature, and solids are better at forming plaques in your arteries and interacting with cholesterol in the bloodstream.

Moving onward to hydrogenation, to my current understanding, if you hydrogenate vegetable oil all the way, you get saturated fats (no double bonds anywhere because you've shoved in so much hydrogen to occupy all the bonds). But for the purposes of making trans fats, it's usually partial hydrogenation.

I assume that most vegetable oils that get partially hydrogenated must be polyunsaturated fats to begin with (meaning more than one double-bond) because partial means you aren't replacing all the double bonds, so there must be at least two double-bonds present.

The result of partial hydrogenation means you remove these double bonds and start straightening out the chains, which makes them easier to stack (which is why trans fats tend to be solid or semisolid), like saturated fats.

My question:

Why are trans fats worse than saturated fats? It looks as though partial hydrogenation is simply taking a polyunsaturated fat and bringing it closer and closer to the status of a saturated fat, but not all the way. If the goal is to get a fat that is solid and lasts longer, why not just use a saturated fat?

And for whatever reason saturated fats aren't the answer: Isn't the end result of partial hydrogenation technically just another unsaturated fat? I thought unsaturated fats were considered healthy? So how are trans fats worse than fully-stackable saturated fats?

Or upon reflection maybe my question is, why are trans fats considered so much worse than other unsaturated fats? If all hydrogenation does is break up double bonds and insert hydrogen, straightening out any cis-kinks in the chain, doesn't this just generate the same acid with fewer double bonds and straighter chains? How is this any different than going out in nature and finding the same unsaturated fat, rather than going to the trouble of converting?

What's causing the difference, here? Where is my understanding breaking down?


texts:
I was provided with the following structure of an inorganic metal complex:

And asked to give information on its NMR spectrum shown below

The highfield signal is caused by a singlet with Platinum ($I = \frac{1}{2}$) due to the terminal $\ce{CH3}$ groups.

As $\ce{^{195}Pt}$ has an abuance of $33.8\%$ this meant that in $66.2\%$ of cases, the singlet will not split, whereas in around $33.8\%$ of cases a doublet would be observed due to the satellites, which would have intensities of $\frac{33.8}{2} = 16.9\%$ hence the "Triplet" was in the ratio of around $16:67:16$.

The low-field signal however for me was easy to deduce but more difficult to calculate ratios for.
The Methyl's could couple to

No $\ce{^{195}Pt}$ resulting in a singlet
One $\ce{^{195}Pt}$ resulting in a doublet
Two $\ce{^{195}Pt}$ resulting in a singlet

The calculations given in the answer are shown:

  No $\ce{^{195}Pt}$ resulting in a singlet: intensity $0.66 \times 0.66$
  One $\ce{^{195}Pt}$ resulting in a doublet: intensity $2 \times 0.66 \times 0.33$
  Two $\ce{^{195}Pt}$ resulting in a singlet: intensity $0.33 \times 0.33$
  This results in a final ratio of 1:8:18:8:1

These calculations confused me.
Why would for a singlet, the intensity be $0.66 \times 0.66$ if both $\ce{CH3}$ give the same signal and hence for the doublet would I need to multiply $0.66 \times 0.33$ by $2$?

These calculations also seemed erroneous.
The calculation for the intensity of the doublet and singlet give the exact same answer and I could not reach the final ratio.

What is the logic behind these calculations?


texts: How was pH measured back in the day if you had nothing to calibrate to?

texts: We learn about indicators but these seem awfully useless if you have no clue what pH the color change occurs at. How did early chemists figure this out? I guess more broadly, how was the hydronium content even measured in the first place?


texts: What is it meant by “preparing solutions on a blister”?

texts:
I was recently looking into an aspirin hydrolysis preparation lab and noticed the following:

(This preparation was taken from http://www.kii3.ntf.uni-lj.si/analchemvoc2/file.php/1/HTML/SPEKTRA/kinetics2.htm)
What is it meant by blisters, and by extension, the droplets? Does this simply indicate a ratio of added solutions? For example, to prepare 9mL of 12.5 mg/L concentrated salicylic acid solution, I would add 1mL of solution A, to 1mL of solution B, to 7mL of distilled water? Does this sound right?


texts: What is the procedure to create stock solutions?

texts:
Until now to execute this recipe, each time i had to count those milligrams/Liter. An enough difficult procedure.

I am posting here this question to help me understand the procedure of creating stock solutions. So the next time i will create that plant substrate, to take a specific volume of that stock solution.

Thank you.


texts: Calculating stoichiometry of a reaction between xenon and fluorine

texts:
Xenon and fluorine were mixed in a 1:1 ratio by volume and sealed in a vessel attached to a barometer. After some time, crystals were found to have formed on the walls of the vessel and the barometer showed that the pressure had dropped to 70% of the original pressure. Analysis of the gases remaining indicated 4 parts xenon to 3 parts fluorine. Construct a balanced equation for the reaction. Assume constant temperature throughout.

Equal volumes of gas at same temperature and pressure have the same number of molecules, thus I deduce that the mole ratio of the 2 gases initially is 1:1. Since $pV = nRT$ then the number of moles of the two gases combined would be 70% of the total number of moles of the 2 gases at the start of the experiment.

I am unsure of how to proceed from here.


texts: Why is phosphorous pentoxide a dehydrating agent?

texts:
$$\ce{HNO3 + P2O5 -> 2HPO3 + N2O5}$$
In this reaction, both nitrogen and phosphorus have the same oxidation number before and after the product is formed. Since the $+5$ oxidation of nitrogen is unstable, it has to undergo reduction, but here it remains the same after the product is formed. So what makes the reaction go forward?
Is it because of the dehydrating property of $\ce{P2O5}$?
Why does this compound have this property and why doesn't $\ce{N2O5}$ have this dehydrating property?


texts: Which carbocation is more stable, the ethyl- or 1-propyl-carbocation?

texts:
$\ce{C2H5+ vs \ C3H7+}$
There are two conflicting trends here.

Inductive effect of ethyl will be higher than that of methyl so carbocation attached to ethyl (3 carbons in total) should be more stable.

On the other hand 3 hyperconjugation structures can be drawn for the carbocation attached to methyl (2 carbons in total) and only 2 hyperconjugation structure for the other.

Which effect wins? I searched a lot of books but didn't find anything.


texts: Help in drawing resonance structures in case of polybasic acids

texts:
While drawing resonance structure of dibasic or tribasic acid, e.g. should I take out two $\ce{H+}$ (in dibasic) or three $\ce{H+}$ (in tribasic) together or one by while drawing resonance structure?

Do dibasic acids give both $\ce{H+}$ at once or one by one?

Actually, I was drawing resonance structure of $\ce{H3PO4},$ but got confused. Should I remove all three protons at once or only one?


texts: How do I setup the electrodes for cyclic voltammetry on a capacitor made on dry copper sheets?

texts:
I'm trying to measure capacitance of a cell I'm creating. It's composed of two copper-sheets with nano-material coated on one side, sandwiched with a membrane and wetted with $\ce{KOH}$. All of the three electrode setups I've found on the internet are for solution based voltamettry, but this cell is not in a solution. The setup that my labmates had yesterday had the reference electrode, $\ce{Ag|AgCl}$ setting in a solution, and not connected to the cell, which doesn't make any sense to me.

What reference electrode should be used to do this kind of measurement, and what should the schematic look like for our setup?


texts: Do nitrogen and oxygen react to form nitric oxide or nitrous oxide?

texts:
In many books it's written that:

$\ce{N2 + O2 -> 2NO}$

and in many others it is written that:

$\ce{2N2 + O2 -> 2N2O}$

Which one of these is actually formed?

Or

Is it that both are formed in variable amounts, but depending on certain reaction conditions one is formed more than the other?


texts: Is a liquid in a container always in equilibrium with its vapour?

texts:
This is essentially a question about the meaning and significance of the term vapour pressure (or vapor pressure if you're American). From what I understand a liquid in a container will have a certain amount of its vapour above it exerting a certain pressure: the vapour pressure - which is dependant on the identity of the substance and the temperature of the system only. The point at which the ambient pressure equals the vapour pressure the liquid boils - the liquid is in equilibrium with its vapour/gas phase (the line in the diagram separating liquid and gas).

However, this had me slightly confused because in the situation initially described (at a point somewhere within the liquid region - NOT on the phase boundary) some vapour existed above the liquid in the container and thus there must be some kind of equilibrium already existing. So, when the ambient pressure equals the vapour pressure nothing has changed in the sense that equilibrium remains present it's just that the pressure is no longer significant enough to facilitate the liquid.

Is what I've said above correct? Mainly in the definition of vapour pressure being the pressure of the vapour above the liquid AT ANY POINT in the liquid region on the phase diagram and also whether the vapour pressure is just a function of temperature.


texts: Grignard formation and vicinal dihalides

texts:
So let's say I have a symmetric 1,2-dihalide (the halides are identical) and I wanted to make a Grignard and I only add 1 eq. of magnesium metal ...

Will I get 1 eq. of asymmetric Grignards (i.e. only one side of the product has the C-MgBr bond) as my product or will:

a) Some of the product be "double" Grignards - i.e. both sides of what used to be the 1,2-dihalide now have C-MgBr bonds?

b) I get some E2 elimination product from Grignards robbing protons from unreacted 1,2-dihalides?

c) A combination of the above?

d) Something else entirely?

Let's say the above reaction works the way I want it to and we get the 1 eq. of asymmetric Grignard reagent.

We then react it with a carbonyl containing compound such as acetone ... do we get an epoxide? Are there even any routes to an epoxide? This suggested as a possible product ...

But I don't see the epoxide.


texts: How are the parameters of a force field obtained for the bond angle HCH?

texts:
In my head, I can't see molecules that I could vary the HCH bond angle without varying other bond lengths, angles and dihedrals to build an energy vs. HCH bond angle curve.

If I vary a single HCH angle of a simple methane molecule, for example, I would automatically be varying the other HCH angles of that same molecule, which would affect the construction of the actual energy vs. HCH bond angle curve.

I may be talking nonsense.


texts: What do chemical constituent measurement units 'g%g' and 'µg g⁻¹' mean?

texts:
I'm trying to understand the following data being presented in this paper measuring the mineral content of the Cannabis sativa plant (leaves and inflorescences):

I need to interpret these data readings in terms of simple percentages.

What would the first two examples - sodium and potassium - translate to in simple percentage / ppm etc.?


texts: Nucleophilicity Of Amino Acid Side Chains

texts: Out of the side chains of aspartic acid, methionine, threonine, and tyrosine, which is the least nucleophilic?


texts: Does MEK-toluene system create a negative deviation from Raoult's law?

texts:
From the experimental data obtained in our lab, when pressure is plotted against mol fraction and partial pressure, it exhibits a negative deviation from Raoult's law which must mean that the forces between MEK and toluene are attractive. But all the info I've found on the internet says that the deviation is positive.

Is MEK soluble in toluene? And could you please give me chemically similar systems.


texts: Why is T-shaped geometry preferred to trigonal planar geometry for the bonds around atoms with 3 bonds and 2 lone pairs?

texts:
This is regarding a situation where an atom has five electron domains; two domains are lone pairs, and three are bonds to other atoms.
The course materials I am using (focusing on VSEPR theory) suggest that, as a rule of thumb, T-shaped geometry is the configuration the electron domains around an atom will take in the above situation. However, that feels unintuitive to me, because the separation between the lone pairs (which ought to repel everything else more strongly) is not maximised in that configuration - it makes more sense in my head that a trigonal planar geometry of bonds would be adopted, with a lone pair above and below the plane of the bonds, to minimize the repulsion between those two lone pairs, as well as to distance the three bonded atoms further apart.
Why, then, is T-shaped geometry preferred in most cases? Is that really the case, or a misrepresentation on the part of the course materials? Many thanks.


texts:
I was reading about stereoisomers and I came across a term pseudo chiral centre.  I looked up on the net for its definition and found a weird formula for calculating no. of isomers if the compound has a pseudo chiral centre.
I can't understand how to deduce the formula and how to do analytically instead of using the formula in case of complex molecules say of more than 3 chiral carbon atoms.


texts: What is the voltage of an electrochemical cell at equilibrium?

texts:
I am having a hard time understanding what happens at equilibrium in an electrochemical cell (a full cell with two electrodes). At equilibrium, according to Nernst equation, the cell potential is $E_{cell}=E^0_{cell}-\frac{RT}{zF}lnQ_r$. Is this cell potential equal to the voltage of the cell ? At equilibrium, the voltage is zero, so does it mean that $E_{cell}=0$ and that both half cells have the same potential ? I am confused about this, as I also understood that $E_{cell}$ at equilibrium is the electromotive force of the cell, which means that it isn't zero.
Thank you for your help !


texts: Why in discussions of percent character of bonds, are only ionic and covalent bondings discussed? Do bonds not have a partial metallic character, and are either metallic and ionic-covalent?


texts: Is the reactivity of Benzene with an -N(R)₃⁺ group greater than its reactivity with an -NH₃⁺ group?

texts: Both are m-directors, and Electron Withdrawing groups, but which one is more reactive? At first sight, one might think clearly $\ce{-N(R)_3^+}$ is more reactive, but when you factor in that $\ce R$ is actually an o,p-director, hence activator, then I think $\ce{-N(R)_3^+}$ is indeed stronger than $\ce{ NH_3^+}$. I can't seem to find any verification on the internet for this.


texts: Diffusion of CO2 and O2 in Water/Atmosphere System

texts:
Consider the following experiment:

One reservoir of pure water is interfacing the atmosphere at standard condition.
Both are at rest and at the same temperature.
Both have no internal gradients (ie: constant concentrations, temperature, ...)
The interface between them is a perfect flat surface (for sake of simplicity).
The dissolved $\ce{CO2}$ in the water has a concentration somewhere between 0-50ppm.
The dissolved $\ce{O2}$ in the water has a concentration somewhere between 0-11ppm.

Questions
in order of importance

How to mathematically model the $\ce{CO2}$ and $\ce{O2}$ rate of change per unit area (flux) in the water and in the atmosphere considering only diffusion?
Suppose the atmosphere is at constant velocity relative to the water reservoir. How this would change the mathematical model above?

Notes: Analytical methods would be appreciated instead of 'heavy' computer simulations.


texts: Molar concentration calculation with absolute uncertainty

texts:
A solution of $\ce{F-}$ is prepared by dissolving $(0.0933\pm0.0004)\ \mathrm g$ of $\ce{NaF}$ $(M= (41.989\pm0.001)\ \mathrm {g/mol})$ in $156.00\pm\ \mathrm{mL}$ of water. Calculate the concentration of $\ce{F-}$ in the solution and its absolute uncertainty.

First of all, uncertainty aside, I got $0.0141$ for the concentration of $\ce{F-}$. However, this is not the correct answer (according to Sapling Learning).

Furthermore, what technique should I use to find the absolute uncertainty?


texts: How is it possible for a substance to have a high heat of vaporization but a low boiling point?

texts:
The final paragraph of Dissenter's question here is worthy of standing alone:

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

(It's similar to this old question by Friend of Kim, but different in that it emphasizes an apparent contradiction.)


texts: Why does the carbonyl group in an acid anhydride have two stretching frequencies?

texts: The carbonyl stretching frequencies for an acid anhydride are approximately $1820~\mathrm{cm^{-1}}$ and $1760~\mathrm{cm^{-1}}$. These are both higher frequencies than a simple ketone owing to the electron withdrawing capability of the adjacent group. However, why are there two distinct infrared stretching frequencies?


texts: Francium has isotopes so how can its atomic mass be a whole number?

texts: Why do francium, radon, radium, and actinium have whole numbers for average atomic mass even though they have isotopes? But then elements like beryllium, fluorine, and sodium are listed as having no isotopes but yet they have a decimal for their average atomic mass?


texts:
There is a process named solar furnace pyrolysis which is used to reduce the oxides of various elements by concentrating solar energy. Oxygen is liberated but an oxide slag is left.

$$\ce{SiO2 ->[pyrolysis] SiO + 1/2O2}$$

How can the element can be extracted from the oxide produced?

I am making a project for NASA on space settlements in solar furnace pyrolysis. Can solar furnace pyrolysis be used for obtaining both metals as well as oxygen from the metal containing oxides left after pyrolysis? Can it be done by electrolysis? If possible, please provide with a link with your answer.


texts: What is meant by the term 'biosynthetic origin'?

texts:
I keep seeing the term biosynthetic origin used in medicinal related papers.
Does it just refer to the biological precursors to the molecule?
So, for example, the biosynthetic origin of Paclitaxel is terpenes?


texts: During electrolysis, why are the products attracted to the cathode?

texts:
Take the electrolysis of Lead(II) bromide:

We can write it as two half-reactions:

$$\ce{Pb^{2+}(l) + 2e^{-} \rightarrow Pb(l)}$$

$$\ce{Br^{-} \rightarrow Br + e^{-}}$$

In the electrolysis reaction, lead is formed at the cathode and bromine is liberated at the anode. But why is it so? I mean, before gaining or losing electrons to become neutral, lead is positive and bromide is negative. So, naturally they should be attracted to the cathode and the anode respectively.

But why do they become neutral after they reach the electrodes. Why do they gain electrons at only the electrodes to become neutral?


texts: What is vacuum-assisted ultrasonication?

texts:
This quote from a methods section of a paper:

[samples were] ultrasonicated for approximately 30 min to ensure
adequate dispersion of the components throughout the mixture. The
solution was then degassed under vacuum-assisted ultrasonication for 1
h to ensure removal of residual oxygen from the mixture...

I know what ultrasonication is. I know what degassing is - bubbling N2 through the solution.
When the author is suggesting vacuum-assisted ultrasonication am I right in my understanding that what they are suggesting is to use a pump to reduce the pressure of the solution during ultrasonication? I imagine this aids gas release by further reducing the partial pressure of the solution.

Is there special equipment for this? I'm not sure the membrane I use
to seal the cuvette will be sufficient hold a strong vacuum.
Should I lower the pressure enough for the solution to boil?
What rate of nitrogen is reasonable? Is this like to defeat the purpose of the vacuum?
What difference will this make compared to ultrasonication and n2 flow through the solution at ambient pressure  - is the vacuum likely to be worth the effort?


texts: Configuration Interaction matrix composition from electronic configurations

texts:
The six electronic configurations below could all be found in the matrix elements of the CI matrix at CISD level. How do I construct the 6 x 6 CI matrix composed of these six configurations and which of the elements will be zero?
How different would it be if I used MP4(SDTQ) method?


texts: Which of the following hydrocarbons react with sodium in liquid ammonia?

texts:
Problem

The hydrocarbon which can react with sodium in liquid ammonia is
(1) $\ce{CH3CH2CH2C#CCH2CH2CH3}$
(2) $\ce{CH3CH2C#CH}$
(3) $\ce{CH3CH=CHCH3}$
(4) $\ce{CH3CH2C#CCH2CH3}$

Solution

 Solve it as a case of terminal alkynes, otherwise all alkynes react with sodium in liquid ammonia.

Question
I know sodium in liquid ammonia is used to produce trans-alkenes from alkynes. But from the options, it seems all of them react with sodium in liquid ammonia.
The solution doesn't make any sense to me. If all of the alkynes given react with sodium in liquid ammonia, then why the question? And what difference does it make if the alkyne is terminal?


texts:
$\ce{CaCO3(s) -> CaO(s) + CO2(aq)}$

It is said that the number of constituents for this reaction is three .
I think number of constituents refer to the number of different elements in the system . As there are 3 different species so it is three.
But for the number of components it is said that as $\ce{CaCO3 and CaO are both in solid state they form only one component}$ and the other component is $\ce{CO2 which is in aqueous form}$
So there are 2 components .
I couldn't completely understand what is number of component ?
And is the above definition of number of constituents is correct ?


texts: Why is the helium wavefunction a linear combination?

texts:
the general solution for the wave function of Helium is a linear combination of the two possible states:

$$
\text{state 1:} \quad \psi_a(\vec{r}_{1}) \, \psi_b(\vec{r}_{2}) \\
\text{state 2:} \quad \psi_a(\vec{r}_{2}) \, \psi_b(\vec{r}_{1})
$$

(where $\vec{r}_{1}/\vec{r}_{2}$ denotes electron 1/2.)

But aren't the products of these wavefunction the same? Why then make a linear combination; it would be just like same function +/- same function?

$$
\psi_a(\vec{r}_{1}) \, \psi_b(\vec{r}_{2})
=
\psi_a(\vec{r}_{2}) \, \psi_b(\vec{r}_{1}) \, ?
$$


texts: Model CO2-C6F14 Vapor Liquid Equilibrium with an Equation of State

texts:
I'm trying to model the VLE for a binary mixture of CO2 and C6F14 using a cubic equation of state (e.g. Peng-Robinson) for both the liquid and the vapor phase (phi-phi approach).

From available data in literature I know that at 30°C and at a pressure ranging from 5 bar to 60 bar the system shows VLE.

In the first step I assume ideal mixture.

When I apply the equation of state to either C6F14 and CO2 to evaluate the fugacity coefficients for the liquid and for the gas phases I obtain only one root so that seems that there isn't any equilibrium.

Where am I wrong? Am I missing something from theory?
Any help is appreciated.


texts:
Hygroscopy is the ability of a substance to attract and hold water molecules from the surrounding environment.

For cotton there is capillary action.
Hydrates like KOH attract water due to lower energy.
What are other possible reasons?
Particles like - diesel fuel, glycerol, salt, sugar and H2SO4 are also hygroscopic?
I have tried to find the reason, but I cant?


texts: Does a grain of salt have exactly equal amount of sodium and chlorine? I know that the formula unit of salt is 1:1, but for example if there is 10000000 atoms of sodium is it possible that that there is 9999999 atoms chlorine? Thanks.


texts: Balmer's formula and lagurre polynomials

texts:
How can you explain the Balmer's formula using the properties of Laguerre polynomials?
It's a homework question but I really don't get it.
1.What is the property of the Lagurre polynomials in the first place?
2.How is Balmer's formula related to the Lagurre polynomials??


texts: Are van der Waals coefficients independent of temperature?

texts:
In the van der Waals equation for real gases, the coefficients $a$ and $b$ are used as respective correction terms for pressure and volume in the ideal gas equation.

I want to know whether the van der Waals coefficients are independent of absolute temperature or not.


texts: Extract seaweed iodine from petroleum ether and cyclohexane

texts: I'm working on iodine extraction from seaweed by using petroleum ether and cyclohexane. I have already observe the presence of iodine in the solution but I don't know how to extract the iodine in a solid form. I try to boil it but it does not work because there is no iodine left after the process. Hope to get the answer ASAP since I'm at nick of time


texts: I want to learn basic chemistry, so which textbook do you think I should pick? It should be something both concise and clear. Thank you.


texts: Determining number of unique hydrogens in lactupicrinal 1H NMR

texts:
I'm having trouble understanding which hydrogens are magnetically distinct in the following molecule (lactupicrinal):

I've counted all the hydrogens (there are 20) and I know that hydrogens in a methyl group are all chemically the same (I think), but I don't know about the hydrogens in the ethyl group (double bonded on the lower right side). Am I right in that all other hydrogens outside of those groups are distinct, or are the mirrored hydrogens on the benzene ring also equivalent? Please help, I'm completely at a loss and I've been trying desperately to understand hydrogen equivalence for weeks.


texts: On what basis can we say that one nuclide is more stable than another one?

texts:
I read in a textbook that the nuclide $^{40}_{20}\ce{Ca}$ is more stable as compared to $^{30}_{13}\ce{Al}$. I checked it online and saw that most sources describe the observation with respect to odd and even number of protons in $\ce{Al}$ and $\ce{Ca}$ respectively.

What is the reason for this? Is it due to proton-proton repulsions overcoming the attractive forces between nucleons?


texts: Beer-Lambert law absorption by each species

texts:
Light travels length $l$ through a medium with $n$ independently absorbing species with extinction coefficients $\alpha_1,\dots,\alpha_n$. According to Beer-Lambert law, the amount of light absorbed is
$$1-T=1-\exp\left(-l\sum_i \alpha_i\right)=1-\prod_i\exp(-\alpha_i l)$$
How do I find the amount of light absorbed by each species? Is it
$$I_{Ai}=(1-T)\frac{1-\exp{(-\alpha_i l)}}{\sum_i {[1-\exp{(-\alpha_i l)}]}}$$
This is the only self-consistent expression I can think of but I don't know if or why it is correct.


texts: Is it safe to heat fluorite (CaF2) to 140 °C?

texts:
For the manufacture of the optical system, we need to heat the fluorite ($\ce{CaF2}$) lenses to $\pu{140 °C}$. Is it possible:

for some poisonous gas to be emitted? ($\ce{F2, HF}$ or other)
for defects to appear on the glass? (scratches, chips, cracks and the like)

If yes, please supply sources describing the corresponding scenarios.


texts: What are the differences between diesel and unleaded gasoline?

texts:
I am curious about the flammability of diesel fuel and its properties, as I don't deal with it on a regular basis (at all).

In particular, I want to know how the fuel works when powering a diesel engine.

Things I know about gasoline engines:

Compresses gasoline and air
Ignites compressed gasoline and air with spark from spark plug
The ignition pushes the piston back turning the crank shaft

I have heard that diesel is less flammable than gasoline and that diesel engines don't require spark plugs. How does this work?


texts: What is the required HLB on the Griffin Scale of 94% water and 6% mineral oil for producing a stable micro-emulsion?


texts: Difference of Ascorbic acid dissolved or precipitated in Glycerol?

texts:
Difference of Ascorbic acid (AA) dissolved or precipitated in Glycerol?
Referring to pat US20110008445A1
Solution 1
At 25C, AA was dissolved in glycerol and alcohol (subsequently removed by distillation).
The AA was measured using scattered light (JIS K0101 using formazine as ref).
5 µm sized particles of AA were found to be dissolved in the glycerol.

Solution 1a
Solution 1 was aged at 28C for 10 days.
10% AA remained dissolved
90% AA precipitated
25 µm sized particles of AA were found to be suspended in the glycerol.

Solution 1b
Solution 1 was aged at 15C for 10 days.
10% AA remained dissolved
90% precipitated
80 µm sized particles of AA were found to be suspended in the glycerol.

Analysis
A key aspect of the experiment focusses on AA being in two different states:
Dissolved and Precipitated
The implication is that the AA is somehow different, otherwise why mention dissolved and precipitation?
Also, the AA was initially dissolved in glycerol and alcohol.
Therefore the AA was

Dissolved in Glycerol and Alcohol
Dissolved in Glycerol
Precipitated and suspended in Glycerol

Question
Does Ascorbic Acid remain in its usable form, in all three scenarios?
('Usable' relates to applying this concept, of dissolving the AA in Glycerol and Alcohol, as a precursor to AA encapsulation in lecithin emulsion).


texts: Is it possible to dope Ca ions in an NaCl crystal to produce a vacancy defect?

texts: I was just reading about defects and doping in solids and read about the defect in  ionic crystal ($\ce{NaCl}$). There were examples of $\ce{SrCl2}$. Could this also occur with $\ce{CaCl2}$?


texts: Calculating molar mass of an oxidant by iodometry

texts:
I am stuck on a question from the Australian Chemistry Olympiad involving molar mass, shown here:

BTW, this whole paper is available online for free, and is distributed by its owners for free. Just search up: Australian Chemistry Olympiad Papers and look at the past papers.
Anyways, in this question, I am able to solve part a and part b, but part c is a little tricky. I understand how to solve for molar mass: it is simply the mass of the substance divided by the number of moles in the same amount of substance. However, in the solution they use the number of moles of the metal cation M, as well as the subscript variable x. Can someone please describe in detail what this means. If there are any more questions, feel free to comment below. Thanks in advance.
P.S. The answers are not my own, but those from the answer sheet.


texts: Change in internal not zero for an Isothermal process?

texts:
(All energy quantities are in $\pu {kJ/mol}$.)

  One molar $H_2O$ is condensed isothermally and reversibly at $\pu{373K}$. Given $\Delta_{vap}H^\circ_{100^\circ}[H_2O] = \pu{40.656 kJ/mol}$. Find $q, w, \Delta_r U, \Delta_r H$.

Since the process is isothermal $\Delta U = 0$ and $\Delta H_p = q_p = -w_p = -40.656$.

I got $\Delta H_p = q_p$ part correct but

For other two
author used $\Delta H - \Delta n(g)RT = \Delta U = 37.55$ and then first law to get $w = 3.101$.

Why $\Delta U$ is not zero ?


texts: How did ancient chemists know the constitution of various compounds

texts:
During times when there was no spectroscopy of any kind, people did make guesses on the molecular constituency and structure.

For example, John Dalton's original atomic hypothesis was that all elements were mono-atomic and that the atoms in compounds have the simplest possible ratios. However, this was proved to be wrong and later it was recognized that oxygen and various other gases were actually diatomic.

How? How was it deduced that these gases are diatomic. Also how were the constitution of various compounds, in terms of both number and structure discerned?


texts: Justify assuming first-order kinetics for a complex

texts:
For the hydrolysis of $trans-\ce{[Co(en)2Cl2]Cl}$ (and cis) we measured reaction rates via spectrophotometry. Plots of change in absorbance $(\ln(A-A_\infty))$ were used to determine the rate law and the rate for the reaction. Using my data, I created the first-order plot seen below:

The question is for the report was:

Justify assuming first-order kinetics

My explanation was that first-order reactions can be expressed as $$[\ce{A}]=[\ce{A}]_0\operatorname{e}^{-kT}$$
and because the concentration decreases exponentially over time, we can assume its first order. Other rate laws I looked up didn’t show an exponential function, so this seemed like sound reasoning, but I was told I was wrong.
What would be the justification for thinking this is first-order?


texts: Why does water electrolysis use direct current?

texts:
Every source I've found regarding water electrolysis says that it's done using direct current (rather than alternating current), but I haven't found a single source that mentions why.

Obviously, using AC will result in the hydrogen and oxygen being mixed together, so if the goal is to produce separate gases then DC is required. But is that the only reason, or is there some chemical process that works better with DC?


texts:
Is significant figure important for atomic radius calculations?

  Calculate the radius of a vanadium atom, given that V has BCC crystal structure, a density of $\pu{5.96 g/cm^3}$, and an atomic weight of $\pu{50.9g/mol}$.

What if we solve this question with $3$ significant figures and $5$ significant figures? What will be different?

Regards


texts: Structure of dihydrogen peroxy-phosphate ion

texts: In structure of Dihydrogen peroxy-phosphate ion $\ce{H2PO5-}$, shouldn't negative charge be on oxygen linked directly to phosphorus, rather than on oxygen linked through peroxy linkage with another oxygen? Since in former it will be in resonance with $\mathrm{p}\pi-\mathrm{d}\pi$ multiple bond between phosphorus and oxygen, while in latter these is no resonance. But my friend argues with me that it should be on latter, since there will be much higher stabilisation by inductive effect and there are only two canonical structures of $\ce{H2PO5-}$.


texts: Can you literally separate air from soil?

texts: My teacher poured water over some soil and said that the air bubbles prove that soil contains air. However I was wondering if there is a more direct approach to proving that soil contains air, like explicitly separating one from the other. Is there an experiment like this? Also, how would the air look like? I've never exactly "seen" air, so how does one know when the air has been separated? Maybe by making it a liquid (liquid nitrogen)?


texts:
I'm certain that I misunderstand this law. It states that:

$$I = I_o e^{-kb} $$

and after rearranging:

$$ A = ln{I_o}-lnI $$

where $A$ stands for absorbance.

1) Does is mean that when the intensity of the exiting light is very low than the absorbance is extremely high?

2) But from the graphs in my textbook, I've seen absorbance which was up to 1 or 1,2. Does it mean that most objects give little "resistance" to light?

3) My textbook says that molar absorption coefficient depicts the probability that photon will excite the energy states (not their words exactly :) ). Than why is f(c) = epsilon a constant function? Shouldn't more concentration increase the probability of change in energy states in some for example molecule?


texts: Does baking soda permanently eliminate nutritional properties of vitamin C?

texts:
(Please forgive me for asking this if it's obvious, but it's not obvious to me.)
EDIT: I am easily confused by chemistry, so please give me a very simple answer, followed by any lengthy further explanation (if you feel it's needed.) Please pretend you are speaking to a 5 year old. Thank you in advance.
Does baking soda (sodium bicarbonate?) permanently eliminate vitamin C's nutritional properties? This question seems to say baking soda would not. Am I correct?


texts:
I am writing a molecular integral code from scratch. Right now my code have the following structure:

loop over shellpair ab:
    loop over shellpair cd:
        loop over primitive ij in ab:
            calculate E_ij
            loop over primitive kl in cd:
                calculate E_kl
                calculate R_ij_kl
                calculate V_ab_cd_ij_kl
        contract V_ab_cd_ij_kl to V_ab_cd

The above pseudo-code have alot of implicit notation, so let me explain what it means before asking my question.

E_ij and E_kl is the expansions coefficients from the McMurchie Davidson scheme.
R_ij_kl is the Hermite integrals also used in the Mcmurchie Davidson scheme.
V_ab_cd_ij_kl is the cartesian integrals found by (note the equations below are not strictly correct):

$$V_{ab,cd,ij,kl}=\sum E_{kl}\sum E_{ij} R_{ij,kl}$$

And V_ab_cd is the contraction of the primitive to the basisfunction:

$$V_{ab,cd}=\sum_i\sum_j\sum_k\sum_l c_ic_jc_kc_lV_{ab,cd,ij,kl}$$

When calculating integrals of higher angular momentum (above $0$), I make sure to reuse common elements in E and R. I.e. when doing p-type integrals px, py and pz have the first element in common, and it is only calculated once in the recurrence relations of the McMurchie Davidson scheme.

For my implementation of the above pseudo-code even the (ss|ss) integrals are very slow. When doing benenze with 6-31G the (ss|ss) integrals uses 2.5 seconds, which is more than can be justified by the use of Python (accelerated with Numba) instead of a compiled language. I have thought about rearranging and saving more intermidiates in memory, i.e. doing something like:

 loop over shellpair ab:
    calculate E_ab (Here E_ab means all E_ij saved in memory)
    loop over shellpair cd:
        calculate E_cd (Here E_ab means all E_kl saved in memory)
        loop over primitive ij in ab:
            loop over primitive kl in cd:
                calculate R_ij_kl
                calculate V_ab_cd_ij_kl
        contract V_ab_cd_ij_kl to V_ab_cd

In the above by calculating E_ab and E_cd, recomputation of E_ij and E_kl is avoided. At this point I know that I lag some expertise in knowing what is worth it compared to memory usage.

My question is know, what is a proper way of implementing molecular integrals with regard of what intermediates to keep at which points. (I know thing like vertical recurrence relations exist, but these will for obvious reasons not speed on my (ss|ss) integrals).


texts: What happens to chemical shifts of protons close to aromatic systems in ¹H-NMR?

texts:
I have two questions regarding chemical shifts on aromatic systems.

First, what does being near an aromatic system do to protons? If we look at the spectra of 1-napthalenemethanol and then 9-anthracenemethanol, the peak of the two aliphatic protons of the benzylic methylene group get shifted way up. Can someone explain why adding in that third aromatic ring does this?
The spectra:

9-anthracenemethanol
1-naphtalenemethanol

I was also under the impression that protons near electronegative elements would be deshielded and be shifted higher. However in the spectrum of Benzil, the protons para to the carbonyl group are higher shifted than the protons meta to the carbonyl. Why is this? Is it to do with conjugation of the carbonyl with the aromatic ring? I'm having trouble finding a proton nmr in the literature, so there's nothing to compare it to.


texts: How can I- be both a nucleophile and a weak base?

texts: I am just confused as to how $\ce{I-}$ cannot attract $\ce{H+}$, but it can attack a carbocation. It is sharing electrons in both cases, so what is the difference?


texts:
The x, y dimensions of snowflakes get all the attention for obvious reasons, but the z dimension must be interesting too, in its own humble way.  In fact, I have lived more than half a century and never seen anyone refer to snowflakes' third dimension at all!

So I'd like to know what a snowflake's cross-section looks like, and what forces/phenomena make it that way.

There are numerous possibilities:

that snowflakes are a single molecule thick
single crystal thick then grown over with hoarfrost
thousands or millions of nearly identical snowflakes glued together like slices in a loaf of bread
something else

No doubt, the ratio between x and y dimensions is extremely similar across all snowflakes, but an interesting part of the phenomena involved would be that which defines the ratio between x and z dimensions.


texts: What happens when an alkylborane is treated with acetic acid?

texts:
In the hydroboration reactions of alkenes I've seen so far, they were always followed by oxidation with $\ce{H2O2/NaOH}$ (to yield alcohols).

Today I found a peculiar reaction in which acetic acid-d1 was added after hydroboration to give a deuterated product:

I don't quite understand what exactly happens after the hydroboration part. Can someone enlighten me here?


texts: Calculating vacancies in crystal structure

texts:
I have this question on a practice exam. I'm not quite sure how to find the number of vacancies when replacing atoms.

Question:
The stable oxide for lithium is $\ce{Li2O}$. How many oxygen vacancies in $\ce{SiO2}$ will be created if 100 Si atoms are replaced by 100 Li atoms (remember, O has a -2 charge in an ionic material)?

I think that because Li is +1 charge and Si is +4 that when I replace the Si with Li it leaves 150 unbound O. So 150 vacancies? Am I totally wrong?


texts:
I have two questions:

It's said that in p block there's gradation in physical and chemical properties of elements. What is meant by this statement?
Why are the different blocks named s, p, d and f?


texts:
I am extremely confused about these types of forces.

Some websites state that the forces in the covalent bonds of carbon dioxide are inter. Other websites say they are intra?

Also, some websites say that the electrostatic bond between ionic compounds is intra, others say they are inter.

So, which is inter and which is intra?


texts: Can all compounds that plants and animals produce be synthesized in a lab?

texts: I guess a better way to ask the question would be, Are there compounds that exist in biology that humans don't have the capacity to produce in a lab?


texts: Which oxidation states were used when Pauling developed his electronegativity scale?

texts:
Paulings electronegativity is a relative scale, based on the difference in electronegativity between X and Y, $\Delta EN = 0.102 \sqrt {\Delta}$, where $\Delta = (X-Y)_{measured}-(X-Y)_{theoretical}$ bond energies.
But what is the oxidation state of X and Y? Is it an average of the common oxidation states for each element, or is it simply the most common oxidation state? Or do I have it all wrong to begin with?


texts: What determines whether a step in a reaction is reversible?

texts: What makes a step in a reaction not reversible? I'm learning all these mechanisms and having to memorize which steps are reversible. Is there a way to figure out whether it's reversible or not?


texts: Is there a relationship between loss of electrons and EM wave reflection?

texts:
Is there a relationship between the loss of electrons in a cation and the amount of electromagnetic spectrum, a compound of this cation would subsequently reflect or transmit?

For example, any compound with $\ce{Fe^3+}$ ions is dark orange. This must mean compounds with $\ce{Fe^3+}$ reflect the longer wavelengths of the visible light spectrum more strongly, so the range of $\approx\pu{635–590 nm}$.

While a compound with a $\ce{Fe^2+}$ cations is light green. This, I think means that compounds that house $\ce{Fe^2+}$ ions reflect wavelengths of the range $\approx\pu{560–520 nm}$ more than others.

Now,  I am not aware at all of any link between atomic electron loss  influencing the transmission/reflection of wavelengths at all, so it could very well be something else entirely that may instead be influenced by the gain/loss of electron. I do not know.

So is there a relationship between the two? If so, what is it?


texts:
This structure:

     H   H
     |   |
 H - C - C - H
     |   |
 H - C - C - H
     |   |
     H   H

Which would be $\ce{C4H8}$, like butene, but an alkane, because it's functional group is C - C.


texts:
What is the maximum extent of a hydride shift to form the most stable carbocation?

If we consider the reaction between 2-methylpropan-1-ol and $\ce{HBr}$, then of course, the carbocation formed after a hydride shift will be more stable (and lead to the major product). 3-methylbutan-1-ol will also undergo hydride shift to some extent to form the more stable carbocation, but is there a limit to it?

Like can the number of carbons be so much that there is almost no chance to make the product with hydride shift possible? Like consider the scenario below:

What can be the maximum $n$ possible here to make the product with hydride shift possible?


texts:
I saw on Youtube a video where caffeine was extracted from Red Bull using dichloromethane. However, due to dichloromethane tendency to form emulsions with liquid, an inefficient method was used to mix the dichloromethane and the Red Bull to minimize the emulsion.
The video maker stated that an emulsion can be broken by adding a salt, but a salt would also drastically affect the taste of the final product. I was wondering, are there any tasteless edible salts that could have been used to break the emulsion without affecting the flavor?


texts: How to draw the structure and find the oxidation number of Phosphorous in H2P2O7

texts:
Find the Oxidation number of Phosphorus in $\ce{H2P2O7^2-}$.
So I thought of drawing the lewis structure to find the oxidation numbers. Because I wasn't sure if Oxygen was bonded to a Hydrogen or not. Then I realised that the two Hydrogens could be ionised, so I'd be left with $\ce{P2O7^4-}$.
But then when I tried drawing this Lewis structure I got really confused, As I tried to draw it with the two Phosphorus as central atoms and I couldn't make it. (I know I can just use general rules to find oxidation numbers but I feel like lewis structures often give more accurate answers). So could you please tell me how to draw the structure and more importantly guide me through the process. Any help is appreciated, thanks!


texts:
Maltose has a 1,4 glycosidic linkage between two molecules of α-D-Glucopyranose.
My textbook suggests the final name of maltose as

  4-O-(α-D-Glucopyranosyl)-D-glucopyranose

I wanted to know what does "4-O-" stands for ?

I dont think so it provides information about the atoms which are linked and moreover feel that Wikipedia's nomenclature (not IUPAC) :

  α-D-Glucopyranosyl-(1→4)-β-D-glucopyranose

more detailized .


texts: Is there any free GAMESS input file maker for Mac OS?

texts:
My main purpose is to simulate excited state calculations on a molecule with Time Dependent DFT.

I am looking for free software that makes input files for GAMESS. I have tried Avogadro and it works fine (in Extensions> GAMESS > Input Generator > Advanced tab) but it can not make TD-DFT input codes.

I also checked the recommended software by the Gordon Group (here) and tried installing some of them but couldn't install Gabedit at all (I was unable to compile the binary, maybe because I am using Mac OS X Yosemite).  I also tried WebMO but it is available just on iTunes for iOS.

What I need is a software that makes the input code interactively to avoid possible errors.


texts: Why do alkenes with more surface contact have greater London forces?

texts: Why is it that alkenes with greater surface contact have greater London forces? I thought greater London forces were dependent on the size of the molecules, or the number of electrons, rather than the surface contact.


texts: Why do carbonates, oxides, and pure metals precipitate before metal sulfides?

texts:
Water tends to leach metals near the surface and deposit them deeper through precipitation in two layers. The upper layer is usually made of metal carbonates, oxides, and occasionally pure or native metals, while the second and deeper layer is metal sulfides. The following excerpt is summarized above.
Source: "Secondary Enrichment of Ore Deposits" by Samuel Franklin Emmons, which was published in the American Institue of Mining Engineers, Transaction 30, (1901), p. 177-201.
The paper does not go into detailed chemistry for the most part but mentions that the chemistry varies from one morphology of soil/rock to another. The author postulates a thermodynamic reason along the lines of reduction potential that facilitates this stratification:

The actual changes observed by me in a great body of pyrite ($FeS_2$) carrying galena (PbS or Lead(II)Sulfide) in a limestone ($CaCO_3$)country-rock, which had undergone partial decomposition from the periphery inwards, are as follows: the original fresh pyrite or marcasite crystals are first disintegrated and slightly pitted on the surface, then changed to  melanterite or hydrated ferrous sulfate and the galena becomes anglesite. In the outer or more fully oxidized zone, the iron-vitriol has changed in part to yellow, basic sulfate; in part to limonite with a separation of native sulfur.
The theoretical changes that are assumed to take place by the action of waters carrying oxygen or oxidizing agents are: first, an alteration of the iron sulfide ($FeS$) to ferrous sulfate (Iron(II)Sulfate or $FeSO_4$) with the formation of sulfuretted hydrogen (Hydrogen Sulfide? $H_2S$) and sulfur which may have oxidized to sulfuric ($H_2SO_4$)or sulfurous acid ($H_2SO_3$). By further oxidation the ferrous sulfate will become, in part at least, ferric sulfate (Iron(III)Sulfate or $Fe_2(SO_4)_3$), and this in its turn will react upon the remaining ferrous sulfate, or upon the sulfides, and form more ferrous sulfate or sulfates of the other metals which are present. By this cycle of reactions, a supply of both ferric and ferrous sulfates would seem to be provided in the oxidized zone, but the extending downwards of the ferric salts would decrease as the supply of oxygen in the waters became less abundant.
It may be assumed that the sulfates of the metals thus formed would be transported for greater or lower distances, generally in proportion to their solubility, the iron sulfates being the most soluble; next, those of copper and zinc; silver sulfate is less soluble and also more readily decomposed, while lead sulfate is extremely insoluble.


texts: Mustard gas hydrolysis (at a very high rate)

texts:
Explain mustard gas hydrolysis at a very high rate:

  $\ce{Cl-CH2-CH2-S-CH2-CH2-Cl}$

I tried searching online but did not find this reaction anywhere. Can someone explain me the steps/mechanism of this reaction? Even some hints might help.

My attempt:

According to Wikipedia

  Solvolysis is a special type of nucleophilic substitution ($\mathrm{S_N1}$) or
  elimination where the nucleophile is a solvent molecule. For certain
  nucleophiles, there are specific terms for the type of solvolysis
  reaction. For water, the term is hydrolysis; for alcohols, it is
  alcoholysis; for ammonia, it is ammonolysis; for glycols, it is
  glycolysis; for amines, it is aminolysis.

It clearly states that hydrolysis/solvolysis can only be $\mathrm{S_N1}$ or elimination. However I'm wondering how can $\mathrm{S_N1}$ occur on a primary carbon! Morever water doesnt seem to be a strong enough base for elimination. So what will be the preferred reaction mechanism?


texts:
How can I balance this reaction using the algebraic method?

$$\ce{K4Fe(CN)6 + KMnO4 + H2SO4 + H2SO4 -> KHSO4 + Fe2(SO4)3 + MnSO4 + HNO3 + CO2 + H2O}$$

My solution:

$$\ce{a K4Fe(CN)6 + b KMnO4 + c H2SO4 -> d KHSO4 + e Fe2(SO4)3 + f MnSO4 + g HNO3 + h CO2 + i H2O}$$

$\ce{K}{:~} 4a + b = d$
$\ce{Fe}{:~} a = 2e$
$\ce{C}{:~} 6a = h$
$\ce{N}{:~} 6a = g$
$\ce{Mn}{:~} b = f$
$\ce{O}{:~} 4b + 4c = 4d + 12e + 4f + 3g + 2h + i$
$\ce{H}{:~} 2c = d + g + 2i$
$\ce{S}{:~} c = d + 3e + f$

I couldn't solve further than that.


texts: are half of "H2SO4 pH sample problem" webpages just wrong, or am I wrong?

texts:
I did a Google search for "h2so4 pH sample problem" and went through the results, and it looks like about 50% of the webpages "explaining" how to do this problem give the wrong answer when calculating the pH of a solution of $\ce{H2SO4}$.  The incorrect sources either (a) assume that each molecule of $\ce{H2SO4}$ donates only one proton (approximately true only at high concentrations); or (b) assume that each molecule of $\ce{H2SO4}$ donates both protons (approximately true only at low concentrations).  Only about half of the sources do the problem correctly by assuming that all $\ce{H2SO4}$ molecules donate the first proton and then using the second dissociation constant to compute the degree of dissociation of the second proton.

I'm no expert, so am I missing something, or are half of the sources out there just wrong?

Googling "h2so4 pH sample problem", here are the first eight hits after removing pages that did not contain an $\ce{H2SO4}$ sample problem, and how I scored them:

http://che1.lf1.cuni.cz/html/Calculations1112_II_handout.pdf -- says "For $\ce{H2SO4}$: $\ce{[H+]}$ = 2 $\times$ $\ce{[H2SO4]}$" -- incorrect.
https://www.quora.com/How-do-I-calculate-pH-of-10-3-M-H2SO4 -- the top-voted answer also says the concentration of $\ce{[H+]}$ is twice the molarity of $\ce{[H2SO4]}$ which 0.001, which is incorrect.  (This gives the incorrect answer of pH = 2.69; the correct answer is 2.73.)
https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Acids_and_Bases/Monoprotic_Versus_Polyprotic_Acids_And_Bases/Calculating_the_pH_of_the_Solution_of_a_Polyprotic_Base%2F%2FAcid -- uses the second dissociation constant correctly and an ICE chart -- correct
https://www.youtube.com/watch?v=gd8mYfiURx0 -- "Calculating the pH value of 1 M H2SO4" -- also assumes both protons are donated -- incorrect
https://www.youtube.com/watch?v=bfdbmT27L1c -- "Calculate pH of a Strong Acid" -- also assumes both protons are donated -- incorrect
https://web2.0calc.com/questions/what-is-the-ph-of-a-0-00050m-solution-of-h2so4_1 -- uses the second dissociation constant -- correct
If the pH is zero, what would be the normality of a sulphuric acid solution? -- I'm counting this as HALF-correct, because it is assumed that each $\ce{H2SO4}$ molecule donates only 1 proton.  This is approximately true at 1 M concentration, but I think it should be stated explicitly that the second proton doesn't get donated because the concentration is so high
http://www.sparknotes.com/chemistry/acidsbases/phcalc/problems/ -- correctly explains the partial donation of the second proton, so even though they don't show the working out, it's still correct

So it looks like even for just a slightly-non-trivial problem, almost a majority of free online help resources get the answer wrong.  Is there some subtlety I'm overlooking?


texts:
I have a problem with the decomposition reaction of Nitric acid($\ce{HNO3}$) by light.
My problem: is that reaction is a redox reaction?
If it is please tell me the oxidation and reduction (balanced) reactions seperately.


texts: I clean vinyl records with an ultrasonic record cleaning machine. Would propylene glycol be good to use as a surfactant in a 1 - 2 % concentration with distilled water?  Would it harm the vinyl record?  Thanks for your help.


texts: I have a piece of what I have been told is "Woods Metal" it melts at 168F.  I am "curious" about how they make it, how low can the melting temperature be?


texts: What does my textbook mean by saying this about petroleum?

texts:
It reads:

  Petroleum consists of crude oil and natural gas and contains a mixture of up to 300 hydrocarbons, including sulfur and nitrogen compounds. It is formed over thousands of years from the remains of fossilised marine organisms.

Is petroleum a single entity that is simultaneously a gas and a liquid oil compounds? How does that work? It is also a mixture of up to 300 hydrocarbons, so it is a liquid and gas in one? I don't understand? Do they mean that petroleum can be either gas OR it can be either liquid? What about the 'mixture of 300 hydrocarbons bit'. Does that mean you will never extract petroleum of a single hydrocarbon eg pure $\ce{C6H14}$ etc? I haven't revised this in a long time so I forgot..


texts: Phase abbreviations for non-aqueous solutions

texts:
When writing a chemical equation, how do you indicate that a chemical is dissolved in a non-aqueous solvent?

For example, it would be inappropriate to write

X (aq)

when X is dissolved in benzene, since aq stands for "aqueous," implying water soluble. A previous answer provided the potential abbreviation (sol), but I wonder if that is actually correct/commonly used.

How would you indicate that X is dissolved in a non-aqueous solvent?


texts: What is ideal water hardness for brewing coffee?

texts:
While procrastinatingworking, I am wondering whether it is optimal to use softened (or deionized) water for brewing coffee, rather than tap water which is in my area rather hard.

My gut feeling is that extraction of the coffee beans' aromatic molecules will be made more efficient if there are no ions on the water, but is this backed up by science?


texts: Lifetime of a (reversible) hydrogen fuel cell system

texts: I am trying to determine how long a system that constantly converts water into H and O and then back will last, as in roughly how many cycles. Now this system can either be made of say a reversible fuel cell or a non-reversible fuel cell combined with a dedicated electrolysis machine (if there is a difference in lifetime). As far as I can tell, platinum is used (almost) everywhere as catalyst and as far I can determine it seems to corrode somewhat throughout use, especially in terms of splitting the oxygen in the fuel cell. I am no professional though and I can only find limited information so I would appreciate it if someone could please tell me roughly how long a system like this will last and how.


texts: London dispersion forces and distance relationship

texts:
Why is the London dispersion force inversely related to distance but not to the second power but the sixth power? Why is there not an inverse square relationship as there is for Coulombic forces?

Is there something non-Coulombic about London dispersion forces?


texts: Which salt precipitates from a solution of ammonium oxalate and silver nitrate?

texts:
I am supposed to write the precipitation reaction for

$\ce{(NH4)2C2O4 + AgNO3 ->[\ce{H2O}]}$

Is my equation correct? I left out the Spector ions.
$$\ce{4(NH4) + 2 C2 +O4\rightarrow 4(NH4)2CO3}$$


texts: Hydroxide formation: reaction of group 13 elements with water

texts:
I was studying about 13th group elements and I found that in this group Al and Tl react water to form a hydroxide and oxide respectively, but the rest of the elements don't react to form hydroxides.

Can anyone tell me why this is the case?


texts: Determining the value and units of the rate constant

texts:
Consider this initial-rate data at a certain temperature for the reaction described by
$$\ce{2NOBr(g) -> 2NO(g) + Br2(g)}$$
\begin{array}{cc}\hline
\ce{[NOBr]_0 (M)} & \mathrm{Initial \,rate \, of \,Br_2}\, (\pu{M/s}) \\ \hline
0.600 &1.08 \times 10^2 \\
0.750 & 1.69 \times 10^2\\
0.900 & 2.53 \times 10^2\\ \hline
\end{array}
I'm not understanding how to find initial rates from the data given and then use that to find the rate constants. I also don't really understand how this information can give me the orders of reactions, for example when does the number double, stay the same, or quadruple, etc.


texts: What's considered a "higher" level of theory in quantum mechanics calculations?

texts:
Comparing wavefunction-based methods and density-based methods for quantum mechanical calculations, how is "rank" determined?

For example, in wavefunction methods, CCSD(T) is considered a higher level than MP2, which is a higher level than HF.

What about if I'm comparing MP2 to B3LYP? Or if I add dispersion
corrections to the DFT method to use something like B3LYP-D3BJ?
What if I just want to compare different DFT functionals? Is hybrid higher than pure? Is B3LYP higher than PBE0?


texts: Why is benzene called "aromatic"? Why not "circular" instead?

texts: I wish to know why aromatic hydrocarbons like benzene are called aromatic when they can be just called circular to avoid the confusion?


texts:
What can be added to liquid $\ce{CO2}$ to lower the electricity needed to crack $CO_2$ ? Answer: Zirconium dioxide

What form and temperature of $\ce{CO2}$ is best to crack with or without Zirconium dioxide?

https://space.stackexchange.com/questions/19755/can-carbon-dioxide-be-broken-down-by-electrolysis


texts: Is it possible create crystalline solvate of electrons?

texts:
Okay, I know that this reads ridiculous insane, but one can obtain solvated electrons by adding sodium metal to liquid ammonia solution.

The chemical reaction as written in my inorganic chemistry textbook is this:

$$\ce{Na + x NH3 -> Na+ + e(NH3)_x-}$$

A metallic sheen is observed, and it supposed to have an absorption band at about $1500\ \mathrm{nm}$ that expands into the range of visible light corresponding to the solvated electrons.

These electrons can be react with alkynes as very powerful reducing agents to to remove an H from a C joined by a triple bond, also liberating hydrogen gas as such. This occurs in the solution made by an alkali metal, not from pure extracted electrons

$$\ce{RC#CH + e- -> RC#C- + 1/2 H2}$$

So I was wondering if pure electrons can be solvated in ammonia, if anyone could think of any means by which these electrons could be extracted from the layer, still solvated by ammonia, and some reaction chemistry could be used to trap electrons in a carbon cage in the form of a solid? It is already known that potassium can be electrostatically trapped in valinomycin between the carbonyl groups of valinomycin.

While it may be different small molecules have been trapped in fullerenes. If electrons could be solidified via extracting them from the metallic layer in the proposed reaction, and interacting them with a "host molecule" in host-guest chemistry, do you think that these materials would be highly conductive. It seems to me that captured electrons would have a much different chemistry than simply metals like copper which shed electrons when a current runs through them. Perhaps if these electrons could be absorbed into carbon nanotubes, then the conductivity of nanotubes would increase significantly and these electron complexes may be significantly more powerful computationally than silicon chips.

Here is an experiment by the University of Nottingham scientists showing the solvation of electrons: https://www.youtube.com/watch?v=tYjQXjUUvwY

What do you think about this? Any ideas?


texts: Can the RDS be different in different direction in a multi-step reversible reaction?

texts:
The following mechanism is given in Peter Sykes when they are "talking about de-esterification" of an ester where the alcohol part is bulky-

Here the second step is given as RDS. According to me, in the reversed reaction(esterification), this step will remain RDS and so the reaction is bimolecular. Someone argues that RDS will be the formation of carbocation then and so the reaction is unimolecular.


texts: Oxidation of conjugated dienes into carboxylic acids by potassium permanganate

texts:
In the book -  MS Chouhan; Advanced Problems In Organic Chemistry; 11th ed, Chapter Alkenes Q32 - the following reaction is given:

The given solution says that:

  Conjugated dienes on oxidation by $\ce{KMnO4/\Delta}$ give oxalic acid

However, the mechanism for this reaction is not given. Also, the formation of a dicarboxylic acid on the parent ring is not explained. I am also unsure what would the products be in a simpler case like buta-1,3-diene. What products will it give?

I checked the internet but could not find a mechanism for the same. The related question of oxidation of arene subsituents by $\ce{KMnO4}$ is not a duplicate.

What is the mechanism for this oxidation?


texts: Finding the mole fraction of nitrogen in a mixture of nitrogen and oxygen

texts:
Question

The density of a mixture of Nitrogen and Oxygen is $\pu{4.7 g L-1}$.
Its given that $P = \pu{4 atm}$, and that $T = \pu{298 K}$. Assuming both gasses are ideal gasses, what is the molar fraction of nitrogen in this mixture?

Answer

 Mole fraction of nitrogen is 0.82.

My Attempt
I tried using the $PV=nRT$ equation, having $V = 1$ and $n$ being the number of moles of both gasses together.
Then I used a second equation for the density being $D=\dfrac{16n_1+14n_2}{V}$.
However I got a negative answer that is also larger than $1$.


texts: Melting and boiling point trend in Group II

texts:
The following picture shows the melting and boiling point trends down group II elements.

I have added question marks where the variability in data was rather disturbing (over two hundred degrees Celsius), or where the value is simply disputed. Nevertheless, this topic is not about the different results from measurements. Instead, it focuses on the "trend" in general.

For group I, we would say

the number of electron shells increases,
the increasing number of protons is unable to compensate for this fact,
therefore, atomic radius increases and
electronegativity, ionisation energies decrease,
hence the metallic bond is weaker $\Rightarrow$ melting and boiling points decrease
atomisation energy decreases.

Here are the atomic radii and ionisation energies of group II elements.

These (apart from radium) do seem to follow the same logic as in group I, however they do not correlate with the melting or boiling points. Some textbooks claim,

  A good measure for the strength of a metallic bond is its atomisation energy.

Let us have a look.

Sure, this does agree better with the boiling and melting points. But note that it is actually not an explanation! Why do the atomisation energies behave in such a way?

This is where most resources either

ignore the problem altogether by not mentioning it,
give an explanation which is claimed by others to be faulty,
few acknowledge the issue and say no simple explanation is possible.

The faulty explanation

Beryllium and magnesium have crystal lattices that are hexagonal closest-packed (close-packed?). Therefore, they have their own trend. Then there are calcium and strontium which have face-centered cubic lattices. Finally, the pair barium and radium have body-centered cubic structures.

Others say this is not enough, because the differences should not be as significant, especially for magnesium but also for barium. Barium has a 8-coordinated structure but has a higher boiling point than 12-coordinated strontium!

It might also be stated that melting points themselves are not the best estimator of the strength of bonds. The bonds are not all broken, but rather rearranged and "made weaker" as a result.

The question

As of now, is there an explanation for melting and boiling point trends of group II elements? Is there consensus?


texts:
I am studying electron collision with molecules, and came across with notation like this $\left(\mathrm{B}^{1} \Sigma_{u}^{+}, \mathrm{c}^{3} \Pi_{u}, \mathrm{a}^{3} \Sigma_{g}^{+}, \mathrm{C}^{1} \Pi_{u}\right)$ for the $H_2$  molecules and I have no idea what they are.
Is there any textbook that explains what this symbols are?


texts: Create Sodium Hydroxide from Sodium Silicate

texts:
During a reaction I use sodium hydroxide and create sodium silicate as a by-product.

I am curious if there is a way to recycle that sodium silicate into sodium hydroxide?

I am not a chemist, just have to use chemistry and I love it.

My best guess is to use Hydrogen Peroxide and Heat.

or Hydrogen gas.

or maybe even Aqua Ammonia...

For any reaction I have abundant electricity available, to create heat.

I have thought about this for months and stuck in the do-nothing phase until I can get some help from experts and see the reaction on paper.

Any help would be greatly appreciated.


texts: How to solve for concentration of two equilibrium reactions with finite equilibrium constants?

texts:
I have a small problem of equilibrium that I counldn't solve. I want the exact answer. No approximations please.
$$
\begin{array}{ll}
\ce{H2O + H2O <=> H3O+ + OH-} &\quad\left(K_w = 1\cdot 10^{-14}\right) \\
\ce{HNO2 + H2O <=> H3O+ + NO2-} &\quad\left(K_a = 4\cdot10^{-4}\right) \\
\end{array}
$$

Objective: Find the concentration every substance, given that the initial value of $[\ce{HNO2}]_0$ is known. Feel free to insert any numerical value for it, if you wish. I have no idea how to solve for the concentrations, when I have two finite ionization constants. How to solve it?

Of course, in this situation, most people would ignore the contribution of the auto-ionization constant of water (that is, ignore the first reaction), leaving only the second one, which is fairly easy to calculate the concentrations. I do not want that.

The reading of this part is optional. Feel free to skip everything down below if you wish. This is an example that I understood how to solve:
$$
\begin{array}{ll}
\ce{H2O + H2O <=> H3O+ + OH-} &\quad\left(K_w = 1\cdot 10^{-14}\right) \\
\ce{HCl + H2O <=> H3O+ + Cl-} &\quad\left(\mbox{Full Dissociation}\right) \\
\end{array}
$$

Hereby, lets say we had an initial concentration of $[\ce{HCl}]_0$. It will then fully dissociate, thus we shall have: $[\ce{HCl}]_0 = [\ce{H3O+}]_0$. Now we correct considering the water autoionization:

$$
\begin{array}{ll}
[\ce{H3O+}] = [\ce{HCl}]_0 + x \\
[\ce{OH-}] = x \\
\end{array}
$$

We solve for $x$ such that $[\ce{H3O+}][\ce{OH-}] = K_w$. This will give me a quadratic equation, which using bhaskara becomes easy to solve.

Again, most people here would ignore the first reaction. And, in certain circumstances, they could, for instance, find a potentially wrong value of $\text{pH}$. Classical example: Just let $[\ce{HCl}]_0 = 10^{-8}$, and then ignoring water autoionization, it will fully dissociate thus $[\ce{H3O+}]_0 = 10^{-8}$, giving $\mathrm{pH = 8}$. So, we just got a basic $\text{pH}$ after just inserting hydrochloric acid in water!


texts:
If a ligand K[Ag(CN)2] is dissociated.. Which one is correct dissociation equation?

$$\ce{K[Ag(CN)2] -> K+ + Ag+ + 2CN^-}$$

or

$$\ce{K[Ag(CN)2] -> K+ + [Ag(CN)2]^-}$$


texts: I would like to know how I can clean a silk tie at the knot. I presume it got filthy, over time, due to "fatty" fingers. I am looking for answers either based on 1) good theory or 2) personal experience. I am not looking for grandma's advice.


texts: Microscopic and mechanical approach to boiling point

texts:
I am confused as to how I should visualize the boiling process throughout a liquid.

From my understanding, the boiling point of a liquid is when its vapor pressure reaches atmospheric pressure. This makes sense at the surface of the liquid where the pressure of the atmosphere no longer overcomes the pressure of the gas molecules escaping the surface of the liquid, so in some sense it can be thought of, on a conceptual level, as becoming a mixture of "air" molecules and "liquid" molecules.

BUT, how does this account for the formation of bubbles on the bottom of container holding the liquid? Wouldn't the gas that is trapped in these crevices need to overcome to pressure of the atmosphere AND the pressure of the liquid itself (looking at it from a physics perspective as well)? How would this phenomena be explained using vapor pressures?

Furthermore, when gas bubbles form within the liquid, should I think of it as the kinetic energy of those particular liquid molecules are so great that it's "pushing" the surrounding liquid molecules with less kinetic energy?

EDIT: Part of my confusion was that I wasn't sure what the composition of these gas bubbles would be exactly—and yes the assumption is that it is being heated from the bottom. Although now I'm curious what would happen if it was heated uniformly somehow.


texts: When NaHCO3 is added to water should give an H$^+$ ion in water and this should make it acidic. Why is it a basic salt? Does it have something to do with H2CO3 being a weak acid?


texts: Understanding and usage of Arrhenius equation

texts: A widely used rule-of-thumb for the temperature dependence of a reaction rate is that a ten degree rise in the temperature approximately doubles the rate. This is not generally true, especially when a strong covalent bond must be broken. For a reaction that does show this behavior, what would the activation energy be?


texts: What is the difference in Da of ESI analytes with multiple charges?

texts:
This is a follow-up question to Why are isotopes an issue in reading mass spectra?

A follow-up question: electrospray ionization (ESI) produces multiply charged species and charge can be >40 (for the purposes of m/z ratio), and assuming the difference in mass for an isotope is ~1 Da (with each additional neutron for an analyte at a charge of +1 in positive ionization mode) and assuming there is only one additional isotope, would the difference in weight for two isotopes each with a charge +10 be 0.1 Da?


texts: Predicting the spontaneity of non-isothermal reactions

texts:
We use free energy equations -- Helmholtz or Gibbs -- to predict whether or not a reaction is spontaneous. These equations depend on constant temperature.

This forum post describes a scenario where volumes of water at different temperatures are mixed. The $\Delta G$ appears to be positive. (The poster's textbook gives $\Delta G = 99.5 \, \mathrm{Cal}$, a result I've been able to duplicate.) This seems to show that $\Delta G$ doesn't predict spontaneity for non-isothermal reactions.

So what does?


texts: Why is there one octahedral and two tetrahedral positions for every anion in a close packed structure?

texts:
I'm reading about ionic crystal structures with planes of close-packed anions and the interstitial sites for cations. There are two types of interstitial sites: tetrahedral and octahedral. That makes perfect sense. What confuses me is this:

  for each of these anion spheres, one octahedral and two tetrahedral positions exist.

Where does this come from? It would seem that for every new anion sphere added, there is a single new tetrahedral position and a single new octahedral position.


texts:
What is the meaning of a decimal in a subscript in a chemical formulas?

I came across the fractional subscripts in a publication,[1] for example:

  We introduce oxygen into a ferromagnetic metallic glass to form a $\ce{Co_{28.6}Fe_{12.4}Ta_{4.3}B_{8.7}O46}$
   magnetic semiconductor with a Curie temperature above $\pu{600 K}$. "

How do I interpret these numbers?

References:

Liu, W.; Zhang, H.; Shi, J.; Wang, Z.; Song, C.; Wang, X.; Lu, S.; Zhou, X.; Gu, L.; Louzguine-luzgin, D. V.; Chen, M.; Yao, K.; Chen, N. A room-temperature magnetic semiconductor from a ferromagnetic metallic glass. Nat. Commun. 2016, 7, 13497 DOI: 10.1038/ncomms13497.


texts: How can we say that one mole of a substance contains avogadro number of particles?

texts:
I just want to know, what was the procedure through which the value of one mole of a substance was considered as a an aggregate of $6.023\cdot10^{23}$ particles.

Secondly, how do we calculate the volume occupied by one mole of gas?


texts: Can carboxylic acids be used in the aldol reaction?

texts:
A question in a practice paper I did recently showed the aldol condensation of benzaldehyde with ethanoic acid. I think I am right in saying that carboxylic acids do not form enolates because the carboxyl proton is much more acidic and so this reaction could not take place under basic conditions but it is possible to protonate a carboxylic acid and then have it take part in an aldol reaction?

Additionally, is this also possible for acyl chlorides, and if not, why?


texts: Extracting "Crystal Radii" from a CIF file

texts:
I'm currently downloading .cif files from various online databases and using openbabel to convert the fractional coordinates that are in the .cif files into .xyz files.  The typical output will look something like this:

5

Spinel
\begin{array}{c|c c c}
\ce{Mg}      &   1.01054     &   1.01054   &     1.01054\\\hline
\ce{Al}      &   1.01054     & 1.01054     &   1.01054\\\hline
\ce{Al}      &   4.04217     &   4.04217   &     4.04217\\\hline
\ce{Mg}      &   4.04217     &   4.04217    &    4.04217\\\hline
\ce{O}       &   2.11390     &   2.11390    & 2.11390
\end{array}
My problem is that I would like the ionic radii of each element, instead of their name.  Does anyone know of a way to recover this information from the original CIF file or am I just stuck with looking up the radii manually on,
https://en.wikipedia.org/wiki/Ionic_radius ?


texts: Internal treatments of gas cylinders for toxic gas mixture

texts:
The values of toxic components  like $\ce{H2S}$, $\ce{NO}$, $\ce{SO2}$, etc. [in ppm level] get decreased after a while due to adsorption phenomenon. Manufacturers design some internal treatments in order to prevent adsorption to obtain a stable mixture.

Do you have detailed information about different kinds of these treatments or do you know where I could find them?
What are other solutions leading to resolve this problem?


texts: light Intensity and its effects on energy and emitted electron on metal surface

texts:
we have a metal surface with electrons in a specific energy state say X ,now we shine light on it of specific wavelength and intensity.
now what if i double the intensity of light , what would happen to the number of electrons emitted and the average energy of the electrons ?

my guess is that since intensity is doubled, then number of photons emitted also double and the energy also doubles .... but i am not really sure about it


texts: Why do ligands have such a small effect on overall absorption of a complexed ion?

texts:
When a metal cation is complexed, there is strong UV-Vis absorption due to the splitting of its $d$ orbitals, thereby allowing electronic transitions.

My understanding is that ligands contribute very little to overall observed absorption. This is evident, for example, in copper solutions. Copper(II) chloride, copper(II) sulfate, and copper(II) nitrate – all solutions of complexed ions – are all very similar in color and have similar absorption spectra.

I think the simple answer is that transition metals have the capacity to allow for electronic transitions while most ligands do not, but I don't believe it is this simple. Also, it is curious that sulfate, chloride, and nitrate are all colorless when dissolved in solution.

My question is: why do ligands have such a small effect on overall absorption of a complexed metal cation?


texts: What is "detwinning" as a 2D crystallography technique?

texts:
The Phys.org article Iron selenide revealed as 'garden-variety iron-based superconductor' is quoted below. Normally I would hesitate to quote so much but in this case it all seems germane.

Question: What is "detwinning" as a crystallography technique? It seems a bit complicated for 2D crystals, with phrases like "... reasoning that the pressure needed to align the larger sample would also cause the layers of iron selenide to snap into alignment." it sounds like manual re-arrangement at almost the atomic scale.

The article links to Anisotropic spin fluctuations in detwinned FeSe in Nature Materials.

  Tong Chen, a Rice PhD student "detwinned" iron selenide crystals by gluing them atop much larger crystals of barium iron arsenide. Using a 2014 method developed at Rice, the larger crystals are placed under pressure and detwinned, causing the smaller iron selenide crystals to also snap into alignment. Credit: Jeff Fitlow/Rice University

  Physicists refer to this directionally dependent behavior as anisotropy or nematicity, and while structural nematicity is known to occur in iron selenide, Dai said it has been impossible to measure the exact electronic and magnetic order of the material because of a property known as twinning. Twinning occurs when layers of randomly oriented 2-D crystals are stacked. Imagine 100 baseball diamonds stacked one atop the other, with the line between home plate and second base varying randomly for each.

  "Even if there is directionally dependent electronic order in a twinned sample, you cannot measure it because those differences average out and you wind up measuring a net effect of zero," Dai said. "We had to detwin samples of iron selenide to see if there was nematic electronic order."

  Study lead author Tong Chen, a third-year Ph.D. student in Dai's research group, solved the twinning problem by cleverly piggybacking on a 2014 study in which Dai and colleagues applied pressure to detwin crystals of barium iron arsenide. It was impossible to apply the same method to iron selenide because the crystals were 100 times smaller, so Chen glued the smaller crystals atop the larger ones, reasoning that the pressure needed to align the larger sample would also cause the layers of iron selenide to snap into alignment.

  Chen spent weeks creating several samples to test in neutron scattering beams. About 20 to 30 1-millimeter squares of iron selenide had to be aligned and placed atop each crystal of barium iron arsenide. And applying each of the tiny squares was painstaking work that involved a microscope, tweezers and special, hydrogen-free glue that cost almost $1,000 per ounce.

  The work paid off when Chen tested the samples and found the iron selenide was detwinned. Those tests with neutron scattering beams at Oak Ridge National Laboratory, the National Institute of Standards and Technology, the Technical University of Munich and U.K.'s Rutherford-Appleton Laboratory also showed iron selenide's electronic behavior is very similar to that of other iron superconductors.

>


texts: Why do nitro groups preferentially bond through the nitrogen rather than the oxygen?

texts:
In many organic and inorganic molecules which contain a nitro group, the bonding takes place through the nitrogen, which gives the nitrogen "four" bonds, but the $\ce{N-O}$ bonds are delocalized across both oxygens which is obviously quite stabilizing.

That being said, I can't help but notice that if the nitro group bonded through the oxygen like $\ce{R-O-N=O}$, then there is not the same situation where nitrogen has over three bonds and the oxygens only have about 1.5 bonds. Additionally, the $\ce{C-O}$ bond is about $360\ \mathrm{\frac{kJ}{mol}}$ compared to about $310\ \mathrm{\frac{kJ}{mol}}$ for the $\ce{C-N}$ bond.

That means that whatever the explanation is, it needs to make up around $50\ \mathrm{\frac{kJ}{mol}}$ in bond energy. I believe the other bonds present should be pretty similar as far as energy goes.

Finally, when the nitro group bonds through the oxygen, presumably there will be less steric hindrance because the group would be roughly linear. I could imagine that assumption being incorrect though.

I imagine that the answer (when bonded to an aromatic molecule) will have something to do with conjugation of the nitrogen lone pair into the pi system. I would think, however, that the oxygen would have a similar effect.

Looking forward to answers.


texts: Bonding of the complex when both weak and strong field ligand are present

texts:
In the complex $\ce{[Ni(H2O)2(NH3)4]^2+}$ the magnetic moment ($\mu$) of $\ce{Ni}$ is –

Zero

$2.83~\mathrm{BM}$

$1.73~\mathrm{BM}$

$3.87~\mathrm{BM}$

It is easy to find the unpaired electrons and hence magnetic moment if we know the bonding strcture.
$\ce{NH3}$ and $\ce{H2O}$ are strong and weak field ligands respectively according to spectrochemical series. I understand that pairing of electrons occur in the case of strong field ligands and it does not occur in the case of weak field ligands.
Nickel has $\ce{d^8}$ configuration here. I dont understand whether I should pair this electron or not. If I pair this electron, I get this:

If I pair the electron then I have to use one $\ce{3d}$ orbital and one $\ce{4d}$ orbital. I have not used both orbitals for overlap in any other question before so I don't know if that's right. Well, I think it should be because anyway these orbitals will make hybridized orbitals of equal energy for bonding. In that case, we get $\ce{d^2sp^3}$ (octahedral geometry).
If I do not pair the electron, I get $\ce{sp^3d^2}$ hybridization.
I am not sure but is this logic correct that since there are more number of strong field ligands than weak field ligands, pairing will occur?
Should I pair the electrons or not and why?


texts: Does the position of the functional group on the terminal carbon change the nomenclature?

texts:
Consider two alcohols:

$$\rm{CH_3 - CH_2 - OH }$$

and

$$\rm{CH_3 - CHOH - H }$$

In the second alcohol, the hydroxyl radical instead of sticking out from the molecule, is bonded below the terminal carbon, like this
$$\rm{H}$$

$$|$$
$$\rm{R- C- H}$$
$$|$$
$$\rm{OH}$$

Now, this doesn't affect the nomenclature (as far as I know), both will be called $\rm{1-ethanol}$. Clearly, these are isomers. But IUPAC nomenclature is supposed to be completely unambiguous. Or did I go wrong somewhere and there actually is a difference in their naming?

PS: Is there any way to produce structural formulas more efficiently in latex on chemistry stackexchange?


texts: What considerations are made in determining whether to use a sand bath or oil bath?

texts: As suggested by the title, I am curious as to what would make, for instance, a sand bath better suited to a specific heating application/context as opposed to an oil bath (and vice versa). Equivalently, I suppose I am asking what the "pro and cons" of both of these methods would be.


texts:
Given information:

$K_\mathrm{a}(\ce{H2CO3}) = 4.3 \times 10^{-7}$,
$K_\mathrm{a}(\ce{HCO3-}) = 4.8 \times 10^{-11}$,
${{\ce{[Na2CO3]}=0.20\ \mathrm{M}}}$

This was a question in an exam and I'm struggling to understand how to solve it. I understand that $\ce{Na}$ is soluble in water, so $\ce{[CO3^{2-}]}=0.20\ \mathrm{M}$. I also know how $\ce{H2CO3}$ dissociates:

$$\ce{H2CO3 <=> H+ +HCO3- <=> 2H+ +CO3^{2-}}$$

When I try solve it using $K_\mathrm{a}=\frac{[P]}{[R]}$ I get:

$$\frac{\ce{[H+]}^2}{\ce{[H2CO3]}}=1.032 \times10^{-16}$$

Past here I'm not sure. I've been told to find $K_\mathrm{b}$ because it's a base but I'm not sure why that would make a difference. Please could someone make a worked solution or give me some hints?


texts: Multiphasic liquid "flotation" experiment

texts:
I'm trying to create an experiment where two immiscible liquids are mixed and are then separated by density. Most of the container is occupied by the lighter liquid, and the small amount of heavier liquid sinks.

Then, a third liquid, immiscible with the other two is added, in amounts intermediate between the two. This liquid is lighter than both of the other liquids and floats.

However, this 3rd light liquid can wet the dense liquid, and after mixing it carries it upwards to the top of the container, basically creating a flotation process.

Here's a rough sketch of what I want to achieve:

I don't care if after the last step the dense liquid then sinks again through the light liquid. If the dense liquid is elevated, even temporarily, that's good enough.

This is slightly similar to industrial flotation processes that separate ore minerals from a slurry of crushed rock. Air bubbles "wet" surfaces of heavy minerals such as copper sulfides and lead sulfides, and float them to the top of a container. In my case I'm talking about three liquids and not a liquid, solid, and a gas.

The reason I'm asking is that I created something similar at high pressure and temperature (~1 GPa, 1000 C) in a sealed pressure vessel and I'm looking for a good way of demonstrating this phenomenon in a more accessible way.

Is there such a thing? I have access to common (and some uncommon) chemical reagents. The liquids have to be transparent, obviously, to see the entire thing. Preferably coloured, or possible to colour them.


texts: Why don't phenol behave like aniline in electrophilic substitutions?

texts:
As far as I know, many electrophilic aromatic substitution reactions fail to undergo the usual way in aniline. This is due to $\ce{-H2N}$ group being basic (pKa of $\ce{NH3}$ = 38), even it is stabilized by the aromatic ring (resonance). Therefore, it often acts as a Lewis / Bronsted base (becoming a deactivating group), rather than being an activating group. Therefore, reactions like Friedel-Crafts reactions, nitration, sulphonation etc. will not undergo, unless the $\ce{-H2N}$ undergoes acylation.
e.g. Failure of Friedel-Crafts alkylation:

I am pondering why phenol does not behave the same way as aniline does. In my mind, fast proton transfer can happen during nitration and sulphonation (pKa of phenol = 10). It can also behave as Lewis Base and attack AlCl3 (presence of lone pair electrons). (or any other activating groups that the aromatic carbon is directly bonded to an atom that has lone pair electron)

But it seems the truth is that phenol just behaves as a strong activating group. What is wrong with my deductions?
edit:
This post says phenol actually behaves the same as aniline (according to the first sentence from OP), echoed by this website.
This website and Organic Chemistry 9th edition by Wade Jr. only says aniline fails, but not mentioning phenol.


texts:
How could you test that there's oxalic acid in potatoes.For example,

  what chemical reacts to oxalic acid and then what will happen if it
  reacts?


texts:
I have been preparing 150 mM and 30 mM Tris Buffers (pka=8.3).  Using .15 M solutions of both Tris and Tris-HCL.

Here is the information in which I have calculated theoretical pH values as well as collected experimental data.

I used (Ka or Kb)= x^2  / [concentration]-x to solve for the values in solution 1 and 5 of both the concentrated and diluted buffers.
I also used Henderson-Hasselbach for solutions 2-4. For example, solution 2 in 150mM:

pH=8.3+log(.375M unprotonated/1.125 M protonated)=7.822

For the addition of .1 mL 1.25 M HCl I added and subtracted appropriately:

pH=8.3+log(.375-.125M unprotonated/1.125+.125M protonated)=7.50

I am having trouble applying these concepts to a diluted buffer solution. I calculated solution 1 for 30 mM buffers by simply changing the concentration by a factor of 5 (per the dilution factor) while using the ICE table Ka=x^2/ concentration-x.

I need some direction in being able to figure out the pH of the diluted solution and how to calculate the effect of .1 mL 1.25 M HCl addition to each of the dilute solutions.


texts: Getting the pressure of a system by series expansion

texts:
An average number, $N$, of bosons of spin $S = 0$ is conned to a two-dimensional domain
  with surface $A$. The gas is ultrarelativistic with a single particle energy $\epsilon = cp$, where $c$ is the speed of light in vacuum and $p$ is the absolute value of the momentum. Compute the pressure, P, of this system as a function of z, A and T. While still being
  in the high-temperature regime, use the result for $N(z, A, T)$ to find $P(N, A, T)$ (keep up to quadratic terms in N). Discuss your results and the relation
  to the ideal gas law.

$N(z, A, T)$ in function of $z$ has been previously calculated:

$$N = \frac{2\pi A}{(h \beta c)^2}(z + \frac{z^2}{4})$$

Where:

$$\beta = \frac{1}{K_B T}$$

$$z = e^{\beta \mu}$$

The following equation also holds:

$$\frac{P}{K_B T} = \frac{2\pi }{(h \beta c)^2}\sum_{n=1}^{\infty} \frac{z^n}{n^3}$$

With this information we should be able to get $P(N,A,T)$ (keeping up to quadratic terms in N), but I am not getting the stated pressure.

The provided solution is:

$$P \approx \frac{NK_BT}{A} (1 - \frac{N(h \beta c)^2}{16 \pi A})$$


texts: Determining pressure of sublimation of iodine

texts:
The pressure of sublimation of iodine can theoretically be determined by considering the two hypothetical steps: the sublimation of iodine at $\pu{298 K}$, followed by an isothermal expansion of our system until it reaches the sublimation
  pressure.

  a) Determine the enthalpy and entropy change for this process.
  b) Determine the pressure of sublimation.

  Given Data

  Triple point: $\mathrm{12.07~kPa, 113.0~^\circ C}$
  Melting point: $\mathrm{113.7~^\circ C}$
  Boiling point: $\mathrm{184.3~^\circ C}$
  $C_{\mathrm m,p}{\left(\ce{I2 (s)}\right)} = 55.44 \mathrm{~J~K^{–1}~mol^{–1}}$
  $C_{\mathrm m,p}{\left(\ce{I2 (l)}\right)} = 89.38 \mathrm{~J~K^{–1}~mol^{–1}}$
  $C_{\mathrm m,p}{\left(\ce{I2 (g)}\right)} = 36.90 \mathrm{~J~K^{–1}~mol^{–1}}$
  $\Delta_\text{f}H^\circ_\mathrm m{\left(\ce{I2(g)}\right)} = 62.44 \mathrm{~kJ~mol^{-1}}$
  $S^\circ_\mathrm m{\left(\ce{I2(g)}\right)} = 260.6 \mathrm{~J~K^{-1}~mol^{-1}}$
  $S^\circ_\mathrm m{\left(\ce{I2(s)}\right)} = 116.1 \mathrm{~J~K^{-1}~mol^{-1}}$

My Attempt

I have calculated the enthalpy and entropy change for the first step by using Hess's Law. They are $\mathrm{62.44~kJ~mol^{-1}}$ and $\mathrm{144.5~J~K^{-1}~mol^{-1}}$ respectively.

Now for the second step which is the isothermal expansion:

$$\Delta H = -nC_{\mathrm m,p}\Delta T = 0$$

For entropy:

$$\Delta S = nR\ln\left(\frac{V_\mathrm f}{V_\mathrm i}\right)$$

If assume that I have 1 mole of iodine I know what $n$ and $V_\mathrm i$ is but how am I suppose to know what $V_\mathrm f$ is?

Also I am struggling to understand the question. It says isothermal expansion of our system until it reaches the sublimation pressure. How are you suppose to know when it reaches sublimation pressure if it has already sublimed?


texts:
My son and I were using a mini science experiment kit for creating batteries with copper, zinc, and lemonade, similar to the famous lemon battery project.  My son's hypothesis was that the liquid had to taste like lemonade to make a battery, and so he hypothesized (I thought correctly) that lime juice would work, but water and milk would not.

However, when we conducted our tests, the battery successfully ran a digital clock with all three liquids.  I washed the cups and copper and zinc sheets thoroughly between each test, but the non-acidic liquids continued to function as batteries.

Did I do something wrong, or is the liquid not required to be acidic to make a battery?


texts: Comparing strength of the C-H, N-H, and O-H bonds

texts:
$$
\begin{align}
\ce{CH4(g) + Cl(g) &-> CH3(g) + HCl(g)} &\quad ΔH^\circ &= \pu{-14 kJ mol-1}_\mathrm{rxn}\\
\ce{NH4(g) + Cl(g) &-> NH2(g) + HCl(g)} &\quad ΔH^\circ &= \pu{-36 kJ mol-1}_\mathrm{rxn}\\
\ce{H2O(g) + Cl(g) &-> OH(g) + HCl(g)} &\quad ΔH^\circ &= \pu{+40 kJ mol-1}_\mathrm{rxn}
\end{align}
$$

  41. Based on the data above, what can be concluded regarding the strength of the $\ce{C-H}$, $\ce{N-H}$, and $\ce{O-H}$ bonds in the molecules shown?

  (A) The $\ce{C-H}$ bond is the strongest.
  (B) The $\ce{N-H}$ bond is the strongest.
  (C) The $\ce{O-H}$ bond is the strongest.
  (D) Nothing can be concluded without knowing the strength of the $\ce{H-Cl}$ bond.

I am not sure how to approach the problem 41. In exothermic reactions, more energy is released when the bonds are formed in the products than is used to break the bonds in the reactants. So would the answer be B because the $ΔH$ is exothermic and is the greater than $ΔH$ of -14 for A?


texts: How to calculate the cell potential after the reaction has operated long enough for the Fe2+ to have changed by some concentration?

texts:
Consider the cell described below at $\pu{261 K}$:
$$\ce{Fe | Fe^2+ (\pu{0.925 M}) || Cd^2+ (\pu{0.981 M}) | Cd}$$
Given $E^\circ_\ce{Cd^2+ -> Cd} = \pu{-0.403 V}$, $E^\circ_\ce{Fe^2+ -> Fe} = \pu{-0.441 V}$.
Calculate the cell potential after the reaction has operated long enough for the $\ce{Fe^2+}$ to have changed by $\pu{0.383 mol L-1}$.

I have
$$E_\mathrm{cell} = (0.441 - 0.403) - \frac{0.0591}{2}\ln\left(\frac{0.925}{ 0.981}\right) = 0.03974$$
but I'm not sure how to find the $E_\mathrm{cell}$ when the $\ce{Fe2+}$ concentration has changed by $\pu{0.383 mol L-1}$.


texts: Help in understanding first way of changing the state of system

texts:
There is a statement in my book:

THERMODYNAMICS
One way: We do some mechanical work, say $\pu{1 kJ},$ by rotating a set of small paddles and thereby churning water. Let the new state be called $\mathrm{В}$ state and its temperature, as $T_\mathrm{B}.$ It is found that $T_\mathrm{B} > T_\mathrm{A}$ and the change in temperature, $\Delta T = T_\mathrm{B} - T_\mathrm{A}.$ Let the internal energy of the system in state $\mathrm{B}$ be $U_\mathrm{B}$ and the change in internal energy, $\Delta U = U_\mathrm{B} - U_\mathrm{A}.$

By rotating a small set of peddles, let us say we do mechanical work of $\pu{1 kJ}.$ Let the new state then be $\mathrm{B}$ and $\mathrm{A}$ as initial state.
It is found that $T_\mathrm{B} > T_\mathrm{A}.$ Let internal energy of system be $U_\mathrm{B}.$
They say that $\Delta U = U_\mathrm{B} - U_\mathrm{A}.$ Do we assume $T_\mathrm{A} = 0?$
We know $\Delta U = q + W.$ So, is $q = T_\mathrm{B} - T_\mathrm{A}?$
Should we say that work, i.e $W_\mathrm{A} = 0$ and same for $W_\mathrm{B} = \pu{1 kJ}?$
What is the difference in saying $\Delta U$ as internal energy and amount of mechanical work?


texts: Is there any way to quantitatively find when a reaction has completed?

texts:
So I'm designing an experiment for measuring how the reaction time of copper and ferric chloride is dependent on temperature; here's the reaction:

$$
\ce{FeCl3 + Cu -> FeCl2 + CuCl}
$$

The problem I have right now is how to quantitatively measure when the reaction has ended. I know you can visually see when a small copper rod has completely dissolved, but I wanted there to be a quantitative aspect to it rather than qualitative.

I've thought of using a pH probe to see if the PH changes after the reaction takes places and stays static, which I could leverage as an endpoint of the reaction, but the pH probes my school are damaged, I think, since the reading keeps jumping around by about 3 or 4.

If you have measured reaction time in general before, I'd love to hear how you did it.


texts:
My professor had explained to us that a nucleophile always attacks on that carbon connected to an epoxy ring, which would make a stable carbocation, when the given compound with the epoxy ring is in an acidic solution(containing H+)

For example if this is the epoxy ring :

The Nucleophile would attack on carbon A, as if A forms a carbocation, it is more stable than B forming a carbocation, if it is in acidic solution. If not in acidic solution the nucleophile attacks on the less hindered carbon(which is B).

But my book has a contradiction :

In this reaction, C2H5- attacks on the less hindered carbon, not the carbon with more stable carbocation.

Is the book right. Also please explain are the above reactions(that my professor said) with epoxy rings always valid ?

Thanks.