New answers tagged physical-chemistry
3
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Can somebody please explain this statement (about the greenhouse effect)?
The "Global Warming Potential" is a relative measure of how much one gram of given substance affects infrared absorption compared to one gram of carbon dioxide, given the current composition ...
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Calculation of formation heat given molar heat capacities and reaction enthalpy
You can apply the Hess law (Wikipedia, Libretexts), mere saying the change of enthalpy (or more generally any state variable) depends only on the starting and ending state, not on the path how the end ...
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Why does Raman Activity Require Anisotropic Polarizability?
The Raman effect involves scattering of a photon with a change in energy due to vibrations or rotations of the molecule. It is changes in the polarisability ellipsoid (either size, shape or ...
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2
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How does steam distillation work to extract a substance from a mixture, below its boiling point?
With comparable boiling points like for water and benzene mixture at constant pressure, neither of liquids boils when sum of partial pressures of their vapors overcomes air pressure. They are just ...
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How does steam distillation work to extract a substance from a mixture, below its boiling point?
At a given temperature isolated, pure substances have an intrinsic vapor pressure. When 2 or more pure substances are mixed that do not dissolve in each other [ie. each is "isolated"] each ...
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Why does the reaction "pause" when the battery is not connected to a circuit? (or does it?)
In a battery, the zinc and manganese reagents are kept separate, and so the electrons can only flow when both parts of the battery are connected via an electric circuit.
If you take a look at the ...
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Why does the reaction "pause" when the battery is not connected to a circuit? (or does it?)
If no wire is joining the zinc plate and the $\ce{MnO2}$ plate, the whole setup would not be a cell or a battery. It wouldn't produce any anode or any cathode. The whole setup would simply be a ...
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Reaction kinetics exercise for hydrogen iodide synthesis
A mistake must have happened in your calculations, because, when I do them, I obtain :
ln$k_1 = - 8.314$;
ln$k_2 = - 0.100$;
ln$k_1$ - ln$k_2$ = $-8.314 + 0.100 = -8.214$
$\frac{1}{T_1} - \frac{1}{T_2}...
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How to compute solvent reorganization energy in Marcus' non-equilibrium approach?
In SI units then conversion.
see Harrison et al Chemical Physics 116 (1987) 429-448 for equations
...
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5
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In JJ thomson's cathode ray experiment why is the effect of gravity on the electron not considered?
Various versions of Thomson's original article (Philosophical Magazine, 44, 293-316 (1897)) can be accessed freely online, for instance at Google books, or here (link liable to rot).
But you can work ...
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Small (personal) scale sea salt production?
Commercially, it's done by solar evaporation. Take sea water, put it in the sun, wait. In your apartment, even if you don't have direct sunlight, surely there is a warm spot somewhere. The only ...
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4
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How to convert molar volume to volume?
If you have given
the molar volume $V_\text{m}$ in $\pu{cm3 mol-1}$,
the molar amount in $\pu{mol}$,
you get the volume as $V = n \cdot V_\text{m}\ [\pu{cm3}] = 0.1 \cdot n \cdot V_\text{m}\ [\pu{J ...
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Is gas solubility independent of pressure?
Let n be the number of moles of solute dissolved in $n_{solvent}$ moles of solvent (in dilute solution). Then, $$x=\frac{n}{n_{solvent}}$$So, $$P=\frac{n}{n_{solvent}}K$$or$$K=n_{solvent}\frac{P}{n}=...
- 13.1k
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Why reverse reaction is not possible in the case of dissociation of strong electrolytes and thus non existence of ionic equilibrium?
Certain compounds that are considered ionic as solids can form significant amounts of uncharged (but obviously polar) associated species in water solution, and we can measure equilibria associated ...
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Is gas solubility independent of pressure?
You state, it seems that, logically, "increasing pressure leads to an increase in dissolved gas." Your logic is not wrong... an increased mass of gas dissolves.
The confusion is because here,...
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Why reverse reaction is not possible in the case of dissociation of strong electrolytes and thus non existence of ionic equilibrium?
Your thinking is correct. What happens at the extremes of conditions is not understood [or just oversimplified]. Here is a made up example using easy math. Lets give the Ka for a strong acid such as ...
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Why reverse reaction is not possible in the case of dissociation of strong electrolytes and thus non existence of ionic equilibrium?
You seem to be fretting over the definition of strong versus weak electrolytes, the notion of chemical equilibria, and what I'll call exactness.
Let's discuss exactness first. Mathematicians have ...
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3
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How can enthalpy of an ideal gas be independent of pressure?
The statement means that enthalpy is independent of pressure, for an ideal gas, if temperature and the amount of matter are both held constant.
For example, if you have 1 mol of idealium on Earth's ...
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Possible error in textbook question? (Heat transfer)
The log-mean temperature difference arises from your original equation: $$(\frac{T_{out} - T_w}{T_{in} - T_w})=exp(\frac{-\pi{d}L}{m{C_p}{R_H}})$$or$$\ln{\left(\frac{T_{out} - T_w}{T_{in} - T_w}\...
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Possible error in textbook question? (Heat transfer)
I figured out the problem with my working. I used the following equation earlier:
$(\frac{T_{out} - T_w}{T_{in} - T_w})=exp(\frac{-\pi{d}L}{m{C_p}{R_H}})$
This was the wrong equation to use because it ...
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-1
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Possible error in textbook question? (Heat transfer)
Overall resistance $R= 0.4545+0.14+\frac{0.002}{.4}=0.5995\ (m^2C)/kW$
Heat Transfer coefficient $U=\frac{1}{R}=1.6681\ kW/(m^2C)$
log mean temperature difference $=\frac{85-40}{\ln{(85/40)}}=59.7\ C$
...
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What solvents can I use to dissolve Epichlorohydrin rubber and Chloroprene Rubber
For chloroprene (neoprene), you might try chlorinated solvents, e.g., methyl chloride (chloromethane).
Epichlorohydrin has "Inferior resistance to oxygenated solvents," according to River ...
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As electron energy increases, does ionisation energy decrease?
Kinda.
An atom or ion has multiple configurations that can be (very roughly) described as electrons (arrows directed up or down) put into boxes * (representing individual orbitals each capable to ...
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Where does the relation Λm=κV come from? is it experimental?
These equations are definitions:
\begin{align}
\kappa &= G \cdot \frac{L}{A}\\
\Lambda &= \frac{\kappa }{ c} = G \cdot \frac{L}{Ac}\\
c &= n/V\\
\Lambda &= \frac{\kappa V }{ n} = G \...
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First order kinetics
As oxygen is reportedly being created by the first order kinetics, we can write:
$$- \frac{1}{2} \frac{\text{d}[\ce{N2O5}]}{dt} = r = k_\text{r}[\ce{N2O5}]$$
Let substitute $y = [\ce{N2O5}]$:
$$\frac{...
- 39.5k
2
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Accepted
Fractional Distillation Question
Here is an interpretation of the diagram, implemented with two distillation setups (blue and orange):
In the first setup (blue), you have a large amount of your initial mixture, which you have to ...
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Fractional Distillation Question
The use of an arrow in the diagram is probably misleading you. This diagram, for the most part, does not show how a system evolves over time.
This graph with the two red curves describes the ...
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