In which of the following reactions is the entropy change expected to be negative?

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Q: In which of the following reactions is the entropy change expected to be negative?

Solution: The reaction N2(g) + 3H2(g) → 2NH3(g) results in a decrease in the number of gas molecules, leading to a negative change in entropy.

Steps: 8

Step 1: Understand what entropy means. Entropy is a measure of disorder or randomness in a system.
Step 2: Identify the states of matter involved in the reaction. Gases have higher entropy than liquids or solids.
Step 3: Look at the reaction given: N2(g) + 3H2(g) → 2NH3(g). Count the number of gas molecules on each side.
Step 4: On the left side, there are 1 (N2) + 3 (H2) = 4 gas molecules.
Step 5: On the right side, there are 2 gas molecules (2NH3).
Step 6: Compare the number of gas molecules: 4 (left) vs 2 (right).
Step 7: Since the number of gas molecules decreases from 4 to 2, the disorder of the system decreases.
Step 8: A decrease in disorder means the entropy change is negative.