20
votes
Does deuterated water slow down the overall metabolism of a cell?
Yes it would, by a few percent. It may or may not be a goal worth pursuing, but there is more to it.
Different reactions would be slowed down to a different extent. Tiny as they are, these ...
- 31.6k
19
votes
Why is entropy favorable?
Thermodynamics. The second law of thermodynamics states that entropy always increases in an isolated system. This is taken as a fundamental postulate---we simply accept this statement as a fact ...
- 5,511
18
votes
Accepted
Can the idea of entropy be extended to orbitals?
No.
The reason why a gas particle in a large volume has a large entropy is not because it has a lot of space to move around per se. A better explanation is that for a given energy, there are many ...
- 71.9k
15
votes
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Why do the first and second laws of thermodynamics not contradict each other?
It is something of a historical accident that entropy has units of J/K. It came out of the fact that the connection between heat, temperature, and energy was not obvious to early scientists, and so ...
- 1,289
13
votes
Accepted
Why does like dissolve like?
The reason behind this is the hydrophobic effect. Everyone has seen it if they pour a spoonful of vegetable oil into a pot of water, e.g. to cook pasta. As long as nothing is disturbing the vegetable ...
- 68.7k
13
votes
Accepted
Why is entropy favorable?
It appears you're looking for an ELI5-style answer, not an elaborate definition.
Entropy just happens – as long as the universe isn't frozen solid, things will always be moving around, and that ...
- 248
13
votes
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Why is the Standard Entropy of a Proton Zero?
Indeed, it is clear that these values are not... Wait! What "these values"?
You are putting two entirely different things in the same basket. (If your textbook does so, then it does a poor job.) It ...
- 31.6k
12
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Does deuterated water slow down the overall metabolism of a cell?
Yes, the kinetic isotope effect is the main reason due to the differential lowering of the zero point energy in reactants and transition state, which has the effect of increasing, slightly, the ...
- 31.4k
11
votes
Accepted
Why does increasing the temperature of a *solid* increase its entropy?
All right, someone bearing the standard of thermodynamics will give you the equations shortly... From a layman to another, here goes my attempt at a simpler explanation.
Entropy may be seen as the "...
- 2,805
11
votes
Accepted
Infinite Increase in Entropy when Energy added to Absolute Zero
The textbook is referring to the entropy change of the system. While the textbook is correct that absolute zero can never be attained, its statement that the entropy change is infinite is wrong. The ...
- 12.3k
11
votes
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Can someone intuitively explain the reason for the units of entropy (J/K )?
The units of of energy over temperature (e.g. J/K) used for entropy in the thermodynamic definition follow from a historical association with heat transfer under temperature gradients, in other words, ...
- 22.9k
11
votes
Why do the first and second laws of thermodynamics not contradict each other?
Incorrect assumptions
[OP] we see that entropy can be transferred between a system and its surroundings, with $\Delta S_\mathrm{system}=-\Delta S_\mathrm{surroundings}$
This equation is usually ...
- 42.3k
11
votes
Accepted
Why does spontaneity of a reaction depend on temperature?
The issue here is in your definition of entropy. According to your definition:
$$\mathrm dS = \frac{\text{đ}q}{T}.\tag{1}$$
However, there is a small difference.
As you may know, the entropy of a ...
- 7,050
10
votes
Accepted
Why can entropy be measured in joules per kelvin?
The definition of entropy in 'Classical Thermodynamics' is $$\Delta S = \int\frac{\delta Q}{T}$$
The quantity on the left is the entropy change associated with a physical process. $\delta Q$ is an ...
- 8,525
10
votes
Why is entropy favorable?
Do not think of entropy as 'disorder' as this is misleading, better is that it is a 'measure of disorder' but this is equally vague. It is better to think of entropy as the number of ways that '...
- 31.4k
10
votes
Accepted
Why is the molar entropy of hexane lower than that of butane?
There are two factors to consider. Certainly, the dominant factor is that the degrees of freedom available for the molecule to disperse energy into increases as the carbon chain extends. Thinking ...
- 1,570
10
votes
Accepted
Isn't the change in Gibbs free energy for a reversible process zero?
The cycle shown is a classic reversible Carnot cycle. An intuitive reason for the change in Gibbs free energy not being equal to zero for such a step is that the pressure is not constant: the internal ...
- 22.9k
10
votes
What is an example of an exothermic reaction with negative ∆S?
A very simple reaction which is readily accessible for study is the dimerisation of nitrogen dioxide:
$$\ce{2 NO2(g) -> N2O4 (g)}$$
This process is has a standard reaction enthalpy change of $\rm{\...
- 29.2k
9
votes
Accepted
Does increasing the entropy of a system cause it to absorb heat?
I consider watching any video a waste of time, so I'll be judging from your words alone. (Anyway, your question is essentially self-consistent, which is good.)
Yes, entropy is a measure of disorder (...
- 31.6k
8
votes
Accepted
Derive expression for internal energy of mixing and entropy of mixing using statistical thermodynamics
In the solution there are two types of molecules $N_1$ and $N_2$. Assume that they do not interact with one another but simply occupy particular 'lattice' sites by blocking them. The total number ...
- 31.4k
8
votes
Accepted
Why can't a reaction go to completion?
You alluded to the answer when you mention activation energy. Kinetically the equilibrium constant is $K_e = k_f/k_b$ where $k_f$ and $k_b$ are the forward are reverse reaction rate constants in the ...
- 31.4k
8
votes
Accepted
What is the entropy of mixing a gas into the whole atmosphere?
Performing an actual calculation could be quite complicated, even if we use the ideal gas approximation, because the atmosphere has enormous variations in both temperature and density.
To simplify ...
- 12.3k
8
votes
Why is the molar entropy of hexane lower than that of butane?
It is a problem of phase.
The standard entropy of butane is $\pu{310 J mol-1 K-1}$ in the gaseous phase.
The standard entropy of hexane is $\pu{296 J mol-1 K-1}$ in the liquid phase. But it is $\pu{...
- 30k
7
votes
Na(s) vs NaCl(s) Entropy
If you don't mind me asking, why would you expect the $\ce{Na}$ to have a higher entropy than the $\ce{NaCl}$? The entropy of a state is defined as,$$S=k_b\ln W$$where $W$ is the number of possible ...
- 13.2k
7
votes
How does refrigerator actually work?
Refrigerators work by exploiting some properties of compressible gases.
To simplify greatly, gases tend to heat up when they are compressed and liquefied. And, when the liquid revapourises this ...
- 37.8k
7
votes
Can someone intuitively explain the reason for the units of entropy (J/K )?
Entropy isn't "just" a measure of randomness. It is the only physical property that gives the universe a temporal direction, i.e., that provides an "arrow of time".
Also, a "measure of randomness" ...
- 12.3k
7
votes
Why do the first and second laws of thermodynamics not contradict each other?
Entropy is not energy. Entropy times temperature has energy units. Entropy can be regarded as a statistical property of thermodynamic systems. Although such a definition is not necessary to apply the ...
- 22.9k
7
votes
Does entropy contribute work?
Suppose you have an ideal gas in a container in mechanical and thermal equilibrium with its surroundings (same $T$ and $p$—say, 298 K and 1 atm). It can't do any work on the surroundings.
Now ...
- 12.3k
6
votes
Why can't a reaction go to completion?
Macroscopic view:
$$\Delta G = \Delta G^{\varnothing} + RT\ln Q$$
As the reaction progresses, $Q$ gets larger so $\Delta G$ becomes more positive. At some point, $\Delta G = 0$ but this happens ...
- 17.6k
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