Identify sign of entropy changes for the following processes.
1) freezing water to form ice
2) ideal gas allowed to expand in a closed container at constant T
3) mixing of two gases into one container
4) NH₂ (g) (1atm) → NH₂ (g) (3 atm)
5) gas mixture transferred from larger to smaller container

• A. 1) −∆S, 2) +∆S, 3) +∆S, 4) −∆S, 5) −∆S
• B. 1) −∆S, 2) −∆S, 3) +∆S, 4) +∆S, 5) −∆S
• C. 1) +∆S, 2) −∆S, 3) +∆S, 4) −∆S, 5) +∆S
• D. 1) +∆S, 2) +∆S, 3) −∆S, 4) +∆S, 5) −∆S

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the concept of entropy (∆S). Entropy is a measure of the disorder or randomness in a system. Processes that increase disorder typically result in a positive change in entropy (+∆S), while processes that decrease disorder result in a negative change in entropy (−∆S).
2. Step 2: Analyze the process of freezing water to form ice. Freezing is a phase transition from liquid to solid, which decreases the disorder of the molecules as they become more ordered in the solid state. Therefore, the entropy change for this process is negative (−∆S).
3. Step 3: Consider the expansion of an ideal gas in a closed container at constant temperature. When a gas expands, the molecules have more space to move around, increasing the disorder. Thus, the entropy change for this process is positive (+∆S).
4. Step 4: Examine the mixing of two gases into one container. Mixing increases the randomness as the molecules of the two gases distribute throughout the container, leading to a positive change in entropy (+∆S).
5. Step 5: Evaluate the process of a gas mixture being transferred from a larger to a smaller container. This reduces the space available for the gas molecules, decreasing their freedom to move and thus decreasing the disorder. Therefore, the entropy change for this process is negative (−∆S).