( Which of the following processes are accompanied by an...

( Which of the following processes are accompanied by an increase in entropy of the system? (No calculation is necessary.) (a) Dry ice, $\mathrm{CO}_{2}(\mathrm{~s})$, sublimes at $-78^{\circ} \mathrm{C}$ and then the resulting $\mathrm{CO}_{2}(\mathrm{~g})$ is warmed to $0^{\circ} \mathrm{C}$. (b) Water vapor forms snowflakes, $\mathrm{H}_{2} \mathrm{O}(\mathrm{s}) .$ (c) Iodine sublimes, (d) White silver sulfate, $\mathrm{Ag}_{2} \mathrm{SO}_{4}$ $\mathrm{I}_{2}(\mathrm{~s}) \longrightarrow \mathrm{I}_{2}(\mathrm{~g})$ precipitates from a solution containing silver ions and sulfate ions. (e) A partition is removed to allow two gases to mix.

( Which of the following processes are accompanied by an increase in entropy of the system? (No calculation is necessary.) (a) Dry ice, $\mathrm{CO}_{2}(\mathrm{~s})$, sublimes at $-78^{\circ} \mathrm{C}$ and then the resulting $\mathrm{CO}_{2}(\mathrm{~g})$ is warmed to $0^{\circ} \mathrm{C}$. (b) Water vapor forms snowflakes, $\mathrm{H}_{2} \mathrm{O}(\mathrm{s}) .$ (c) Iodine sublimes,
(d) White silver sulfate, $\mathrm{Ag}_{2} \mathrm{SO}_{4}$ $\mathrm{I}_{2}(\mathrm{~s}) \longrightarrow \mathrm{I}_{2}(\mathrm{~g})$
precipitates from a solution containing silver ions and sulfate ions. (e) A partition is removed to allow two gases to mix.

Key Concepts

Entropy

Entropy is a measure of the disorder or randomness of a system. It quantifies the number of microscopic configurations that a system can have. Higher entropy indicates more ways for the system’s particles to be arranged, leading to increased disorder.

Phase Changes and Entropy

Phase changes involve transitions between different states of matter, such as solid, liquid, and gas. These transitions affect the system's entropy because higher phases, such as gases, typically have more disorder than solids or liquids. Processes like sublimation or vaporization generally increase entropy as the particles have greater freedom of movement.

Entropy of Mixing

When different substances, especially gases, mix, the overall randomness of the system increases due to the increased number of possible arrangements of the particles. This increase in configurational possibilities leads to a rise in the entropy of the system, which is commonly observed when barriers preventing mixing are removed.

Transcript

00:01 So here we're giving examples of different chemical reactions.

00:03 We're asked to determine the change in entropy.

00:06 So for our first reaction, we have dry ice, which is co2 in its solid form, and we undergo essentially sublimation.

00:15 So it's basically the conversion from the solid form to the gaseous form.

00:20 So as we know, gases are widely dispersed, and it's hard to essentially pinpoint down the motion of a gas.

00:28 Gases have larger, basically, vibrational possibilities for vibrational motion and rotational motion compared to a constrained solid.

00:36 So in turn, the entropy of a gas is greater than the entropy of solid form.

00:45 And remember that the change in entropy is the sum of the entropy of the products minus the entropy of the reactants.

00:51 So this would imply that the change in entropy is greater than zero for this reaction.

01:00 So for part b, so we're given information that we're cooling down water vapor to form solid, basically the solid form of water.

01:14 So this would be an example of deposition reaction, which is the reverse of sublimation.

01:21 So this is the complete opposite of the first reaction.

01:24 So the entropy of gas is essentially greater than the entropy of solids.

01:31 But since the entropy is on the reactant side in this case, and this would be equivalent to the entropy of the solid minus the entropy of the gas.

01:42 And since the entropy of the gas is greater than the entropy of the solid, the change in entropy for this process would be less than zero.

01:52 For part c, we're given information that iodine sublime, so we're converting iodine from its solid form to its gaseous form.

02:01 So this is once again an example of a sublimation reaction.

02:05 So this is the same for the first example.

02:08 So entropy would increase...

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