state function that is a measure of the matter and/or energy dispersal within a system, determined by the number of system microstates; often described as a measure of the disorder of the system

possible configuration or arrangement of matter and energy within a system

process that takes place so slowly as to be capable of reversing direction in response to an infinitesimally small change in conditions; hypothetical construct that can only be approximated by real processes

Chemistry 2e · 16.2 Entropy

Entropy: practice problems

7 problems from the book, with its answers. Check your working, or have any of them explained to you on the whiteboard.

Exercises 7
In Figure 16.8 all of the possible distributions and microstates are shown for four different particles shared between two boxes. Determine the entropy change, ΔS, for the system when it is converted from distribution (b) to distribution (d).
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Exercises 9
Consider a system similar to the one in Figure 16.8, except that it contains six particles instead of four. What is the probability of having all the particles in only one of the two boxes in the case? Compare this with the similar probability for the system of four particles that we have derived to be equal to $\frac{1}{8} .$ What does this comparison tell us about even larger systems?
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Exercises 11
Consider the system shown in Figure 16.9. What is the change in entropy for the process where the energy is initially associated with particles A and B, and the energy is distributed between two particles in different boxes (one in A-B, the other in C-D)?
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Exercises 13
At room temperature, the entropy of the halogens increases from I₂ to Br₂ to Cl₂. Explain.
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Exercises 15
Indicate which substance in the given pairs has the higher entropy value. Explain your choices.
(a) C₂H₅OH(l) or C₃H₇OH(l)
(b) C₂H₅OH(l) or C₂H₅OH(g)
(c) 2H(g) or H(g)
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Exercises 17
Predict the sign of the entropy change for the following processes. Give a reason for your prediction.
(a) $Na^{+} (a q) + Cl^{-} (a q) ⟶ NaCl (s)$
(b) $2 Fe (s) + \frac{3}{2} O_{2} (g) ⟶ Fe_{2} O_{2} (s)$
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Exercises 19
Write the balanced chemical equation for the combustion of benzene, C₆H₆(l), to give carbon dioxide and water vapor. Would you expect ΔS to be positive or negative in this process?
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Key terms · 3

entropy (S): state function that is a measure of the matter and/or energy dispersal within a system, determined by the number of system microstates; often described as a measure of the disorder of the system
microstate: possible configuration or arrangement of matter and energy within a system
reversible process: process that takes place so slowly as to be capable of reversing direction in response to an infinitesimally small change in conditions; hypothetical construct that can only be approximated by real processes

Learn 16.2 on the whiteboard

The tutor teaches the whole section, drawing it out step by step and answering your questions as you go.

Read 16.2 in the textbook · This section on openstax.org

Entropy: practice problems

7 problems from the book, with its answers. Check your working, or have any of them explained to you on the whiteboard.

Exercises 7

In Figure 16.8 all of the possible distributions and microstates are shown for four different particles shared between two boxes. Determine the entropy change, ΔS, for the system when it is converted from distribution (b) to distribution (d).

Exercises 9

Consider a system similar to the one in Figure 16.8, except that it contains six particles instead of four. What is the probability of having all the particles in only one of the two boxes in the case? Compare this with the similar probability for the system of four particles that we have derived to be equal to $\frac{1}{8} .$ What does this comparison tell us about even larger systems?

Exercises 11

Consider the system shown in Figure 16.9. What is the change in entropy for the process where the energy is initially associated with particles A and B, and the energy is distributed between two particles in different boxes (one in A-B, the other in C-D)?

Exercises 13

At room temperature, the entropy of the halogens increases from I₂ to Br₂ to Cl₂. Explain.

Exercises 15

Indicate which substance in the given pairs has the higher entropy value. Explain your choices.

(a) C₂H₅OH(l) or C₃H₇OH(l)

(b) C₂H₅OH(l) or C₂H₅OH(g)

Exercises 17

Predict the sign of the entropy change for the following processes. Give a reason for your prediction.

(a) $Na^{+} (a q) + Cl^{-} (a q) ⟶ NaCl (s)$

(b) $2 Fe (s) + \frac{3}{2} O_{2} (g) ⟶ Fe_{2} O_{2} (s)$

Exercises 19

Write the balanced chemical equation for the combustion of benzene, C₆H₆(l), to give carbon dioxide and water vapor. Would you expect ΔS to be positive or negative in this process?

Key terms · 3

entropy (S): state function that is a measure of the matter and/or energy dispersal within a system, determined by the number of system microstates; often described as a measure of the disorder of the system
microstate: possible configuration or arrangement of matter and energy within a system
reversible process: process that takes place so slowly as to be capable of reversing direction in response to an infinitesimally small change in conditions; hypothetical construct that can only be approximated by real processes

Learn 16.2 on the whiteboard

The tutor teaches the whole section, drawing it out step by step and answering your questions as you go.

Read 16.2 in the textbook · This section on openstax.org