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22
votes
2answers
1k views

Why are silicon analogs of alkenes or alkynes so difficult to make?

We know that there are silicon analogs of alkanes, but according to Wikipedia, silicon analogs of alkenes or alkynes are virtually unknown. How come?
5
votes
1answer
33k views

Phenyl or benzene when naming compounds

These two molecules are both aromatic: However, the first molecule has a halogen substituent and is named "bromobenzene". The second molecule has a chlorine and a hydroxyl group and is named "4-...
6
votes
4answers
30k views

Distance between successive tetrahedral voids in FCC

What is the distance between successive tetrahedral voids in a FCC crystal structure? The distance between a face centered atom and a tetrahedral void is $\sqrt{\frac{3a}{4}}$ if the cube's edge ...
5
votes
1answer
868 views

Why is tin-112 stable, but indium-112 radioactive?

According to Wikipedia, tin-112 is a stable nuclide, but indium-112 is radioactive (half-life only 14 minutes). What is the explanation for this?
22
votes
2answers
6k views

PBP vs TBP geometry?

Why are the axial bond lengths greater than those of the equatorial bonds in a trigonal bi-pyramid (TBP) geometry molecule; but the opposite is true for pentagonal bi-pyramid (PBP) geometry molecules? ...
8
votes
1answer
229 views

Compounds that adopt the zincblende structure

Zinc sulfide, copper iodide and copper bromide all adopt the zincblende structure. My lecture notes suggest that this structure is adopted preferentially over the wurtzite structure if the bonding is ...
-1
votes
1answer
197 views

What is the byproduct from hydrogenolysis of an acyl chloride?

What's the byproduct of this reaction? After all, it is a "lysis" reaction. So ... would HCl be a byproduct?
0
votes
0answers
212 views

How to electronically calculate alcoholic level of a liquid

Is there any way to estimate the alcohol content of a drink with an electric test? Is alcohol in a liquid (e.g wine) dependent on the drink's conductivity?
2
votes
1answer
1k views

Is it possible to find fire outside the Earth?

Excuse me if the question is silly, I have very little knowledge of chemistry. We can find oxygen in many places in the universe, but all the combustibles we use to light fire seems to be organic: ...
4
votes
1answer
3k views

Can carboxylic acids be used in the aldol reaction?

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 ...
21
votes
3answers
7k views

Why is there a difference in the colours of K₂Cr₂O₇ and K₂CrO₄?

In both the compounds the oxidation state of Chromium is +6 so why is there a difference in the colours of their aqueous solutions. $\ce{K2Cr2O7}$ is red-yellow and $\ce{K2CrO4}$ is bright yellow I ...
1
vote
1answer
197 views

Is the correct configuration assigned to the given pair of geometrical isomers of 1,2-dichlorocyclopropane?

I suppose that the configurations assigned are opposite as in the left isomer of 1,2-dichlorocyclopropane, the left chlorine atom is coming out of the plane of the paper while the other is going into ...
8
votes
3answers
642 views

Why does everything go in the direction of positive entropy change?

I read about entropy from different sources. Still don’t get why (universal) entropy change has to be greater than zero for irreversible process, i.e. $\mathrm{d}S_\mathrm{Univ}>0$. Is it a result ...
2
votes
1answer
40 views

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

I'm reading a paper about the atmospheric chemistry on Titan {1}. It quotes "column photochemical and loss rates" for various species in units of $\mathrm{cm^{-2}s^{-1}}$. These figures are the ...
10
votes
1answer
4k views

Why is isobutane more thermodynamically stable than n-butane?

I would like to understand the term stability in organic chemistry. We know empirically that isobutane (2-methylpropane) is more stable than n-butane. For example, their heats of formation (taken from ...
6
votes
2answers
344 views

Interaction radius of a molecule

What is the most commonly used radius of an atom or molecule to describe the area that must touch another area of another molecule for the two to react. Is there one radius that always works or does ...
7
votes
1answer
661 views

Usefulness of the outdated Bohr model?

Whilst the Bohr model is incomplete and incorrect, it had limited usage in predicting spectral lines. In the same way, could it possibly with limited accuracy, be used to predict the outcome of ...
2
votes
1answer
1k views

Titrating and the addition of acidic distilled water

I have read numerous online questions similar to the one I am about to ask. But for most of them the answer has been that the reason one can add water to the unknown concentration solution during a ...
1
vote
1answer
7k views

Molar heat of fusion of ice?

The molar heat of fusion of ice is 6.01 kJ/mol. Can you explain what this means? What I think it means is that it requires 6.01 kJ to melt a mole of ice. I'm not positive though..
-3
votes
2answers
3k views

How to write equations for a reaction of metals with water

Please write two equations for reacting lithium with water and barium with water. Make sure to add the states of matter after each compound. Currently, for lithium I have the equation $$\ce{2Li(s) +...
0
votes
2answers
22k views

How to write equations for dissociation of ionic compounds in water?

Please write a dissociation-in-water equation for the compounds $\ce{BeI2}$ and $\ce{LiI}$. Make sure to add the states of matter after each compound. Currently, for $\ce{BeI2}$ I have the equation $$...
8
votes
2answers
16k views

What is the difference between ΔG and ΔG “with an o on top”? [duplicate]

What is the difference between $\Delta G$ and $\Delta G^\circ$? I couldn't figure it out. Ex: $\Delta G^\circ = -RT\ln K$ $\Delta G = \Delta G^\circ + RT \ln Q$ What is the difference, is it that $\...
0
votes
1answer
14k views

Why is it that increasing the molar mass generally increases the Entropy? [closed]

I've just found read that entropy increases through these reasons: Changing the phase of the elements to a gas. Increasing the molar mass of that specific element increases the entropy. I understand ...
5
votes
1answer
87 views

Protein purification with Cobalt

Cobalt exhibits a more specific interaction with histidine tags, resulting in less nonspecific interaction than nickel. For this reason, cobalt is the preferred divalent cation for purifying His-...
3
votes
2answers
2k views

What's the source of electrical energy in galvanic cells?

Let's take a simple Daniell cell for example: Where does the energy required to drive electrons through the external circuit and power up devices (like a light bulb) come from? Does the oxidation of ...
5
votes
1answer
4k views

Why does the Oxymercuration Demercuration mechanism lead to stereorandomization?

I'm having a doubt on the mechanism of oxymercuration Demercuration reaction. How does the reaction, initially heading towards anti addition(after cyclic transition state formation) ,get spoiled by $\...
1
vote
2answers
665 views

How is a car battery recharged?

When recharging a lead-acid battery, how are the terminals of the battery connected to the voltage source. I mean, do we connect the positive terminal of the battery to the negative terminal of the ...
2
votes
1answer
1k views

Determine the isotope half-life?

A sample of $\ce{^{41}Ar}$, a radioisotope used to measure the flow of gases from smokestacks, decays initially at a rate of 34,500 disintegrations/min, but the decay rate falls to 21,500 ...
2
votes
1answer
666 views

Why does solvent leveling occur?

Solvent leveling means that strong acids completely dissociate in that solvent so it is impossible to distinguish between two acids that completely dissociate in it. A solvent levels and acid if the $...
3
votes
1answer
3k views

Mechanism of enolether formation with ethyl orthoformate in estr-4-ene-3,17-dione (Djerassi's norethisterone synthesis)

The second step of Djerassi's synthesis of 19-nor-17α-ethynyltestosterone (norethindrone), involves the protection of the ketone in position 3 via enolether formation, as in the picture: What is the ...
2
votes
0answers
49 views

What makes a metal more inclined to bond covalently? [duplicate]

Many metals form compounds with s-block elements that are essentially entirely ionic. However, elements like silver, copper, lithium and so on, can form bonds that are significantly covalent in ...
2
votes
1answer
427 views

Exo- or endothermic? Clarification required regarding a few cases

Are the following processes exothermic or endothermic? a) When solid $KBr$ is dissolved in water, the solution gets colder. b) Natural gas ($CH_4$) is burned in a surface. c) When concentrated $...
7
votes
1answer
1k views

Why does iodine have different colors in different media?

It is violet in trichloromethane, but brown in water. why? In the Shriver Atkins book, they tried to explain this using Molecular Orbital Theory which was not clear to me
1
vote
0answers
66 views

How to calculate “accurate” surface area of a microporous material using Micromeritics equipment?

How do I get an accurate surface area from a nitrogen isotherm? I've been doing some surface areas on MOFs and upon showing my boss the isotherms he asked me to convert them to show the "range", ...
1
vote
1answer
106 views

The nuclear Overhauser effect

I am having some trouble with understanding the NOE. The carbon NMR spectra can't be integrated, because the protons attached to the carbon atoms will make primary carbon atom relaxation faster than ...
3
votes
1answer
9k views

Do I have to consider the molecular mass of the oxygen atom or the diatomic oxygen molecule when determining the empirical formula of an iron oxide?

In determining the empirical formula of a compound which constitutes a diatomic molecule, should we calculate the molar mass of the divalent molecule by multiplying the molar mass of the element by 2, ...
4
votes
2answers
5k views

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

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-...
0
votes
0answers
135 views

jury-rigging an automotive catalytic converter for use in the Ostwald Process?

Would it be feasible to jury-rig an automotive catalytic converter for use in the Ostwald Process for the production of Nitric Acid? Given reasonable safety precautions, would it be safe enough to be ...
12
votes
1answer
2k views

Why are inert gas (especially Xenon) compounds powerful oxidizing agents?

I am curious as to why compounds with inert gases, such as $\ce{XeF4}$, $\ce{XeF2}$, and $\ce{XeO3}$ are considered powerful oxidizing agents. I would attribute the phenomenon to the highly oxidized ...
4
votes
1answer
978 views

Finding pH of a buffer

What is the pH of a solution prepared by mixing 25.00 mL of 0.10 M methylamine, $\ce{CH3NH2}$, with 25.00 mL of 0.10 M methylammonium chloride, $\ce{CH3NH3Cl}$? Assume that the volume of the solutions ...
3
votes
1answer
1k views

Household Melting Point Standards

I'd like to accurately calibrate a digital thermometer I'm building in the range of $50^\circ$ to $120^\circ$ Celsius. I'm aware that one can buy various chemicals that have melting points in this ...
5
votes
1answer
2k views

Is 1.5M NaOH a strong enough base to deprotonate benzyl alcohol?

Is 1.5M NaOH a strong enough base to deprotonate benzyl alcohol? I realize that NaOH generally does not deprotonate benzyl alcohol, but we performed an extraction in a Fischer esterification lab with ...
5
votes
3answers
220 views

Iterative method for calculating pH of a weak acid / base

The problem asks to determine the $[\ce{H+}]$ in a $0.20~\mathrm{M}$ solution of $\ce{Na3PO4}$. The $K_\mathrm{a}$ of $\ce{HPO4-}$ was given as $4.5\times 10^{-13}$, which then allows one to calculate ...
2
votes
0answers
116 views

In entropy change of surroundings, what is T?

This question is simpler than the previous one about intuition of entropy; I just need to know whether the $T$ term in $dS_{Surr} = \frac{-dH}{T}$ refers to the temperature of the surroundings or the ...
1
vote
1answer
129 views

Understanding a passage related to salt buffer

Passage from my textbook: Are reactions possible among any of the solution components; is so, what is their stoichiometry? Suppose that you are asked to calculate $[\ce{OH-}]$ in a solution that is ...
5
votes
3answers
700 views

Truly Understanding the Second Law of Thermodynamics and Entropy

There are some seemingly contradictory things I’d like cleared up: Second Law states: $\mathrm dS_\text{univ} = \mathrm dS_\text{sys} + \mathrm dS_\text{surr}$, and $\mathrm dS_\text{univ}$ is always ...
5
votes
1answer
809 views

Effect of different electron withdrawing/transition state stabilising groups in nucleophillic aromatic substitution

I have been asked the following question in my problem sheet: The only differemce between reaction A and reaction B is the electron withdrawing group that stabilises the anionic transition state ...
3
votes
1answer
6k views

How to determine whether the enthalpy of solution is positive or negative by calorimetry?

How can we determine if the enthalpy of solution of a compound is positive or negative? In order to make a clear idea about what I mean, take the following problem: A 3.5 g sample of $\ce{NH4NO3}$ ...
5
votes
1answer
4k views

Calculate the number of moles produced per hour per liter of air?

A reaction of importance in the formation of smog is that between ozone and nitrogen monoxide described by $$ \ce{O3(g) + NO(g)->O2(g) + NO2(g)} $$ the rate law for this reaction is: $$ \text{...
1
vote
1answer
4k views

Is p-bromophenol more acidic than p-chlorophenol?

p-chlorophenol is more acidic than p-fluorophenol due to presence of vacant d orbitals. But then is p-bromophenol more acidic than p-chlorophenol since it has vacant f orbitals also? But I guess that’...

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