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We know that dilute $\ce{ H2SO4}$ doesn't react with copper because copper has higher reduction potential ($0.33$) as compared to hydrogen ($0.00$).
However, it reacts with conc. $\ce{H2SO4}$ and gives $\ce{CuSO4}$ with $\ce{SO2}$ and $\ce{H2O}$.
Why does this reaction take place? |
Usually there are two explanations:
1) When dipoles are induced due to movement of electrons in the molecule, they are bigger in molecules with more mass since they have/include more atoms (has sense to me)
2) Bigger molecules have bigger contact or "surface area"
What does "surface area" between molecules have t... |
Why are Dispersion Interactions Stronger in Molecules with Bigger Molecular Mass? |
> $K_m$ is the lowest concentration of substrate needed to ensure that the system runs at $V_{max}$?
No. $V_{max}$ is never reached, it is the limit of the rate when you increase the substrate concentration indefinitely. Less dramatically said, when the substrate concentration is about ten times higher than $K_m$, t... |
> $K_m$ is the lowest concentration of substrate needed to ensure that the system runs at $V_{max}$?
No. $V_{max}$ is never reached, it is the limit of the rate when you increase the substrate concentration indefinitely. Less dramatically said, when the substrate concentration is about ten times higher than $K_m$, t... |
Mechanically _yes_, considering the weight, pouring from a smaller Dewar is easier than from a larger one. It takes some practice to aim, of course. Using an additional plastic funnel consumes some of LN2 because the funnel obviously has to be cooled before LN2 passes the bottom of the chute.
Not knowing your expe... |
While solving some problems on general organic chemistry, I came across this question that asked for the nature of inductive effects of $\ce{-CH_3}, \ce{-CO_2^-}, \ce{-Br}, \ce{-NH_3^+}$.
And in the solution to that problem, it says $\ce{-CO_2^-}$ shows $\ce{+I}$ effect.
How is it possible that the carboxylate ... |
Why does the carboxylate ion show positive inductive effect? |
How does redox couple develop its potential if electrode isn't the part of the redox system like platinum in SHE or Cl2/Cl- in water solution for example? Usually it is discussed how electrode develops its potential when it isn't inert like Cu/Cu2+ system when copper electrode itself is important for developing potenti... |
How is Electrode Potential Developed on Inert Electrode? |
So, let's take a solution of copper sulfate in a beaker and insert an active electrode: a copper wire. OK so far? We connect this wire to a voltmeter.
Then lets connect another wire (we are quite well off, even rich, so we will use a shiny platinum wire) to the other connection of the voltmeter. Platinum is nice, in... |
The expression of RMS velocity clearly has square root of number of gas molecules in the denominator and square root of squares of velocities of the gas molecules in the numerator. Then why RMS velocity does not depend on number of gas molecules? By looking at the expression, it seems as if it does depend on number of ... |
Does RMS velocity depend on number of gas molecules in a gas sample? |
A problem asks, if you have a positive delta S (positive change in entropy) for an exothermic (meaning a negative delta H, or negative change in enthalpy) reaction and temperature increased, what would happen to Keq and Keq/Q (where Keq is the equilibrium constant and Q is the reaction quotient)?
The answer states t... |
Why is Keq going up in this exothermic reaction? |
>What is the relationship between given pair of molecules?
They are enantiomers as given underlined answer.
>How did you know that?
You know that by assigning $R/S$ configuration (following Cahn-Ingold-Prelog rules) on each chiral carbon. That is the easiest way to identify the enantiomers. If you have one ch... |
>What is the relationship between the following pair of molecules? Is the underlined answer correct? Explain.
[![Enantiomers of 1-bromo-3-methylcyclohexane][1]][1]
I'm getting mixed answers. Some say these are identical molecules. Other say these are enantiomers. Which is correct and why?
[1]: https:/... |
Enantiomers or identical structures? |
>What is the relationship between given pair of molecules?
They are enantiomers as given underlined answer.
>How did you know that?
You know that by assigning $R/S$ configuration (following Cahn-Ingold-Prelog rules) on each chiral carbon. That is the easiest way to identify the enantiomers. If you have one ch... |
>What is the relationship between given pair of molecules?
They are enantiomers as given underlined answer.
>How did you know that?
You know that by assigning $R/S$ configuration (following Cahn-Ingold-Prelog rules) on each chiral carbon. That is the easiest way to identify the enantiomers. If you have one ch... |
I'm looking for a table or another kind of schema where I can find which type of carbon atoms (sp3, sp2 etc.) are present in each amino-acid.
In my biochemistry books these informations are not available.
I looked also on pubchem (e.g. [glycine][1]), and I found some information about [alanine][2], [aspartic acid][... |
I'm looking for a table or another kind of schema where I can find which type of carbon atoms (sp3, sp2 etc.) are present in each amino-acid.
In my biochemistry books these informations are not available.
I looked also on pubchem (e.g. [glycine][1]), and I found some information about [alanine][2], [aspartic acid][... |
The depletion laser is at 775nm, and about 500 mW, concentrated for a short sequence of pulses on an area about the size of ~0.2 um^2
As far as I can tell very few organic molecules, nor water, absorb in this range of 775nm.
So why does it cause photodamage?
Thermal damage sure, but why bleaching fluorophores s... |
Why does STED microscopy cause photodamage? |
>What is the relationship between given pair of molecules?
They are enantiomers as given underlined answer.
>How did you know that?
You know that by assigning $R/S$ configuration (following Cahn-Ingold-Prelog rules) on each chiral carbon. That is the easiest way to identify the enantiomers. If you have one ch... |
A problem asks, if you have a positive $\Delta S$ (positive change in entropy) for an exothermic (meaning a negative $\Delta H$, or negative change in enthalpy) reaction and temperature increased, what would happen to $K_{eq}$ and $K_{eq}/Q$ (where Keq is the equilibrium constant and Q is the reaction quotient)?
The... |
STED (stimulated emission depletion) microscopy is a technique which enables sub-diffraction limit of light imaging.
The depletion laser is at 775nm, and about 500 mW, concentrated for a short sequence of pulses on an area about the size of ~0.2 um^2
As far as I can tell very few organic molecules, nor water,... |
A problem asks, if you have a positive $\Delta S$ (positive change in entropy) for an exothermic (meaning a negative $\Delta H$, or negative change in enthalpy) reaction and temperature increased, what would happen to $K_{\mathrm{eq}}$ and $K_{\mathrm{eq}}/Q$ (where $K_\mathrm{eq}$ is the equilibrium constant and $Q$ i... |
Why is the equilibrium constant increasing in this exothermic reaction? |
I am doing a colorimetry experiment with starch, and have a theoretical model based on Beer's law. To solve it, I need a known value for the molar extinction coefficients of amylose and amylopectin. Are these known values, and where can I find them?
While experimentally finding them would not be too hard, I cannot ... |
Is there a known value for the molar extinction (absorption) coefficient for amylose and amylopectin? |
The following mechanism for acyl chloride hydrolysis was given by my professor :
[![mechanism][1]][1]
However I do not understand why in the second step, oxygen has a partially negative charge, should it not gain a positive charge as it is bonded to three atoms, furthermore shouldn't the $\text{O}-\text{H}$ bond ... |
help! what steps do I have to take to do a multi step synthesis of this? |
I am calculating Ka and percent dissociation of acetic acid being diluted to 0.100M, 0.01000M and 0.000100M.
The pH goes up as the weak acid is diluted, which is to be expected.
The % dissociation is inversely related to the initial concentration of acetic acid.
However, I fail to understand why the Ka value in... |
Why is Ka increasing in dilution? |
I am calculating Ka and percent dissociation of acetic acid being diluted to 0.100 M, 0.01000 M and 0.000100 M.
The pH goes up as the weak acid is diluted, which is to be expected.
The % dissociation is inversely related to the initial concentration of acetic acid.
However, I fail to understand why the Ka value... |
Why is Ka of weak acid increasing while being diluted? |
I was recently studying the alpha alkylation of enolates using LDA followed by subsequent treatment with primary halides to give the product.I was wondering what happens with teritary halides. My guess is that elimination will take place,and the carbon nucleophile formed by LDA will abstract a proton fron the tertiary ... |
I want to know if there is a material that expands more than what I've seen. For example, elephant toothpaste is a good reaction, a small amount of two things expands into [seemingly] something with much more volume. I was wondering: What's the most expansive chemical reaction or material? something that expands in siz... |
What material expands the most from a base form? |
Do high-energy chemical bonds indicate strong chemical bonds? |
[![enter image description here][1]][1]
[1]: https://i.stack.imgur.com/CrMqR.png
My approach:
- Both have same number of $\pi$ bonds
- Both have 1 resonating structures
- Both are non aromatic
- In $I$ there are 3 $\alpha$ Hydrogen where as in $II$ there are 4 $\alpha$ Hydrogen, so extent of hyper-c... |
I'm looking for a way to start a small fire with widely available chemicals. It would be great if they are safe to use with metals (not necessarily). But the biggest requirement is that it should be SAFE at medium scales and should not make an explosion.
I have found out `H2SO4 + KMnO4` can start a fire. But is it p... |
I'm looking for a way to start a small fire electronically with widely available chemicals. It would be great if they are safe to use with metals (not necessarily). But the biggest requirement is that it should be SAFE at medium scales and should not make an explosion.
I have found out `H2SO4 + KMnO4` can start a fi... |
Earlier I had a student come by wanting to know how to show the dissolution of $\ce{NH4OH}$ in water. I would think we would just write it: $$\ce{NH4OH(aq) <=> NH3(aq) + H2O(l)}$$ I say this as $$\ce{NH4OH(aq) + H2O(l) <=> NH3(aq) + H3O+(aq) + OH-(aq)}$$ I am struggling to understand when and why we put the $\ce{H2O}$... |
>[![enter image description here][1]][1] [![enter image description here][2]][2]
I know that if the smallest atomic number group is not in the back, we can twist the molecule so that it is in the back and then determine if it is R/S (Left image). But if the chiral center is attached to a ring, can we still simply tw... |
I am calculating $K_\mathrm{a}$ and percent dissociation of acetic acid being diluted to $\pu{1.00 \times 10^{-1} M}$, $\pu{1.00 \times 10^{-2} M}$, and $\pu{1.00 \times 10^{-4} M}$.
The $\mathrm{pH}$ goes up as the weak acid is diluted, which is to be expected.
The % dissociation is inversely related to the init... |
[![enter image description here][1]][1]
[1]: https://i.stack.imgur.com/CrMqR.png
My approach:
- Both have same number of $\pi$ bonds.
- Both have 1 resonance structures.
- Both are non aromatic.
- In $\text{I}$ there are 3 $\alpha$ Hydrogen where as in $\text{II}$ there are 4 $\alpha$ Hydrogen.
... |
How to compare the stability? |
In the Wolf-Kishner reaction the first step is to react the carbonyl with hydrazine to form the hydrazone. The later steps of the reaction requires a strong base to cause loss of nitrogen.
However, the mechanism for the formation of the imine/hydrazone is acid catalyzed:
[![enter image description here][1]... |
How does hydrazine react with carbonyls under basic conditions? |
In the Wolff-Kishner reduction the first step is to react a carbonyl with hydrazine to form a hydrazone. The later steps of the reaction requires a strong base to cause loss of nitrogen.
However, the mechanism for the formation of the imine/hydrazone is acid catalyzed:
[![enter image description here][1]][... |
At what concentration would copper sulphate crystallise at 25 degrees Celsius? |
How is the hydrazone formed in the Wolff-Kishner reduction? |
How to compare stability between 5‐methylcyclohexa‐1,3‐diene and 3‐methylenecyclohexene? |
I'm looking for a way to start a small fire electronically with widely available chemicals. It would be great if they are safe to use with metals (not necessarily). But the biggest requirement is that it should be SAFE at medium scales and should not make an explosion.
I have found out $\ce{H2SO4 + KMnO4}$ can start... |
My textbook says that critical temperature is the temperature above which a gas cannot be liquified no matter how much pressure we apply on it. But why? What is so special about this 'critical temperature'? I mean, if we apply a ridiculous amount of pressure, the gas molecules have to come closer to one another and the... |
Why does not gas liquify at a temperature above the critical temperature no matter how much pressure is applied on it? |
Why BeF2 is highly soluble in water but Be(OH)2 is not ?
Both release Be2+ ion so they have high hydration energies and can easily overcome their lattice energies.
Then why is the latter insoluble ?
p.s explain in simple terms. |
Why is $\ce{BeF2}$ is highly soluble in water but $\ce{Be(OH)2}$ is insoluble?
Both release $\ce{Be^{2+}}$ ion so this means they both have high hydration enthalpies and can easily overcome their lattice enthalpy.
Then, why is $\ce{Be(OH)2}$ insoluble? A simple explanation would be appreciated.
|
I am doing a colorimetry experiment with starch, and have a theoretical model based on Beer's law. To solve it, I need a known value for the molar extinction coefficients of **amylose and amylopectin iodine complexes**. Are these known values, and where can I find them?
While experimentally finding them would not b... |
Is there a known value for the molar extinction (absorption) coefficient for amylose and amylopectin iodine complexes? |
I am calculating $K_\mathrm{a}$ and percent dissociation of acetic acid being diluted to $\pu{1.00 \times 10^{-1} M}$, $\pu{1.00 \times 10^{-2} M}$, and $\pu{1.00 \times 10^{-4} M}$.
The $\mathrm{pH}$ goes up as the weak acid is diluted, which is to be expected.
The % dissociation is inversely related to the init... |
We know that ideal gas equation is $PV= nRT$ where P is the pressure of the ideal gas and V is the volume of the ideal gas. Thus, we can write : $ P_{ideal}V_{ideal} = nRT$. Now from volume correction term of van der Waals' equation we know that $ V_{real} = V_{ideal} - nb $ where $ V_{real} $ is the volume of the real... |
How can we replace volume in ideal gas equation with V - nb? |
So, let's take a solution of copper sulfate in a beaker and insert an active electrode: a copper wire. OK so far? We connect this wire to a voltmeter.
Then lets connect another wire (we are quite well off, even rich, so we will use a shiny platinum wire) to the other connection of the voltmeter. Platinum is nice, in... |
How would a solution made of 20 mL of NaOH, 10 mL of HCl, 10 mL NaH2PO4 and 5 mL of Na3PO4, all of them in a concentration of 10 mmol/L, behave? I already tried every way i can think of, but none give the solution of the pH of this system. |
I am calculating $K_\mathrm{a}$ and percent dissociation of acetic acid being diluted to $\pu{1.00 \times 10^{-1} M}$, $\pu{1.00 \times 10^{-2} M}$, and $\pu{1.00 \times 10^{-4} M}$.
The $\mathrm{pH}$ goes up as the weak acid is diluted, which is to be expected.
The % dissociation is inversely related to the init... |
Wolff–Kishner reduction is the method for the reduction of aldehydes and ketones to corresponding alkanes. First, the carbonyl compound condenses with hydrazine to form the corresponding hydrazone. The resulting hydrazone is treated with base to induce the reduction of the $\mathrm{sp^2}$-carbon to $\mathrm{sp^3}$-$\ce... |
How would a solution made of 20 mL of NaOH, 10 mL of HCl, 10 mL NaH2PO4 and 5 mL of Na3PO4, all of them in a concentration of 10 mmol/L, behave? I already tried every way i can think of, but none give the solution of the pH of this system.
Ways I tried:
1 - After reacting the HCl with NaOH, I use the NaOH that i s... |
We know that ideal gas equation is $PV= nRT$ where P is the pressure of the ideal gas and V is the volume of the ideal gas. Thus, we can write :
$$ P_{\textrm{ideal}}V_{\textrm{ideal}} = nRT$$
Now from volume correction term of van der Waals' equation we know that
$$ V_{\textrm{real}} = V_{\textrm{ideal}} - ... |
The fusion curve of triple phase diagram of water and fusion curve of triple phase diagram of general substances is different. Why is it so?
|
Why is the triple phase diagram of water different from the general substances? |
We know that ideal gas equation is $PV= nRT$ where P is the pressure of the ideal gas and V is the volume of the ideal gas. Thus, we can write :
$$ P_{\textrm{ideal}}V_{\textrm{ideal}} = nRT$$
Now from volume correction term of van der Waals' equation we know that
$$ V_{\textrm{real}} = V_{\textrm{ideal}} - ... |
The Wharton rearrangement presents an opportunity to convert one α,β-unsaturated ketone to its regioisomeric allylic alcohol. To this end Ohloff, *et al.*,<sup>1,2</sup> explored the transformation of α-ionone **1** into α-damascone **2**. Epoxide **3** was exposed to hydrazine in methanol to aff... |
I am calculating $K_\mathrm{a}$ and percent dissociation of acetic acid being diluted to $\pu{1.00 \times 10^{-1} M}$, $\pu{1.00 \times 10^{-2} M}$, and $\pu{1.00 \times 10^{-4} M}$.
The $\mathrm{pH}$ goes up as the weak acid is diluted, which is to be expected.
The % dissociation is inversely related to the init... |
The Wharton rearrangement presents an opportunity to convert one α,β-unsaturated ketone to its regioisomeric allylic alcohol. To this end Ohloff, *et al.*,<sup>1,2</sup> explored the transformation of α-ionone **1** into α-damascone **2**. Epoxide **3** was exposed to hydrazine in methanol to aff... |
I've made carbon electrodes by putting 12V through a couple of short 15Ω pencils, but when I try to make hydrogen and oxygen bubbles from soapy water, I get tiny bubbles, smaller than table salt.
If I move the electrodes closer together, it's the same tiny bubbles, but a bit faster.
These don't catch fire very co... |
How can I get big bubbles when I electrolyse water with detergent? |
If I wanted to perform a Virtual Screening for one molecule and several ligands, take for example, the docking between TDO protein and several antidepressant drugs:
How would I be able to correlate the docking affinity with a physiological effect?
Is it necessary to perform clinical studies also?
I think this ... |
Why is some other quantity like molality or molarity used?
I understand why mass percentage cannot be used as it is difficult to measure mass of gas...
Now is mole fraction used because solubility is directly proportional to the pressure and moles are directly proportional to the pressure?
Also, how do they measu... |
Why is only mole fraction used in Henry's law and not some other measure of concentration? |
> How would a solution made of $\pu{20 mL}$ of $\ce{NaOH}$, $\pu{10 mL}$ of $\ce{HCl}$, $\pu{10 mL}$ $\ce{NaH2PO4}$ and $\pu{5 mL}$ of $\ce{Na3PO4}$, all of them in a concentration of $\pu{10 mmol/L}$, behave? I already tried every way i can think of, but none give the solution of the $\mathrm{pH}$ of this system.
W... |
> 1. How would you deal with a user who produced a steady stream of valuable answers, but tends to generate a large number of arguments/flags from comments?
First I would look at the arguments and see what is the cause. If it's a user deliberately being disruptive, I would definitely warn them. (Repeated disregard o... |
> 1. How would you deal with a user who produced a steady stream of valuable answers, but tends to generate a large number of arguments/flags from comments?
I think the site doesn't work if we can't interact in a civil way, so frequent fights or abusive behavior outweighs useful content. Often these sorts of dispute... |
Regarding COVID-19 and hydroxychloroquine (HCQ), HCQ is known to increase pH in lysosomes by 1-2 orders of magnitude, and also result in lethal intracellular heme overload in parasites responsible for hemolytic diseases. Question is, if circulating levels of xanthine oxidase (XO) are also known to be increased in hemo... |
The fusion curve of triple phase diagram of water and fusion curve of triple phase diagram of general substances is different. Why is it so?
 |
Regarding COVID-19 and hydroxychloroquine (HCQ), HCQ is known to increase pH in lysosomes by 1-2 orders of magnitude, and also results in lethal intracellular heme overload in parasites responsible for hemolytic diseases. Question is, if circulating levels of xanthine oxidase (XO) are also known to be increased in hem... |
Isn't oxidation number a weird concept? It assumes complete transfer of an electron from a more EN to a less EN atom per covalent bond formed. This assumption isn't even true. We know that partial $δ^+$ and $δ^-$ charges develop on the atom. Why did we introduce such a weird concept? And what is it good for? |
Why did we introduce the concept of oxidation number in chemistry? |
As I understand it, the voltage in an electrochemical cell is due to the electrons transferred having a decrease in electrical energy as they go from one species to another. I assume that this change in potential is due to the electrostatic attractions and repulsions of the protons and other electrons of the species re... |
Why does concentration affect voltage from an energy perspective? |
Does equilibrium involve ionisation process? |
I need help with this reaction, I know that in the first step an alpha haloketone is formed, but I can't figure out what reaction is going to happen between the alpha Haloketone and H2O/H+.
[![enter image description here][1]][1]
I read your answers and this is some information and assumptions that I can share.
... |
As I understand it, the voltage in an electrochemical cell is due to the electrons transferred having a decrease in electrical energy as they go from one species to another.
I assume that this change in potential is due to the electrostatic attractions and repulsions of the protons and other electrons of the specie... |
I was recently studying the preparation of amides,and one of the methods listed was acid hydrolysis of a nitrile. Up until now I thought acid hydrolysis of nitriles yielded carboxylic acids. How are the methods to get amides and acids different?
I can view the amide as sort of an intermediary stage while getting to ... |
hydrolysis of nitriles:when amide,when acid? |
As I understand it, the voltage in an electrochemical cell is due to the electrons transferred having a decrease in electrical energy as they go from one species to another.
I assume that this change in potential is due to the electrostatic attractions and repulsions of the protons and other electrons of the specie... |
It's in a phase diagram topic. It's about $\ce{Cu}$-$\ce{Sn}$ phase diagram.
[![enter image description here][1]][1]
And it has a question of:
> Write the schematic diagram describing the following scenarios and identifies the regions and the phases when Slow cooling of $13.1\%$ $\ce{Sn}$ alloy from $\pu{1000^\cir... |
In college, I studied that for an ideal gas $PV = nRT$ , that is, at constant temperature and constant number of moles, $P \propto \frac {1}{V}$. Thus, graph between $P$ and $V$ is a rectangular hyperbola when $dT =0$ and $dn=0$. But in my textbook there is this topic called 'Andrews' isotherms' wherein they have given... |
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