Question

Delta S is positive (increasing entropy) for the reaction _____.

A) CaO(s) + CO₂(g) → CaCO₃(s)
B) 2SO₃ (g) → 2SO₂(g) +O₂ (g)
C) N₂ (g) + 3H₂ (g) → 2NH₃ (g)
D) H₂O (l) → H₂O (s)
E) Ag + (aq) + Cl- (aq) → AgCl(s)

Answer 1

Among the given reactions, the one with a positive entropy change is B) 2SO₃(g) → 2SO₂(g) + O₂(g), as the number of gas molecules increases, indicating increased randomness or disorder.

Step-by-step explanation:

The question pertains to predicting the sign of the entropy change (Delta S) for various chemical reactions. Entropy characterizes the disorder or randomness in a system, and a positive Delta S indicates an increase in entropy. Based on the options provided, let's assess which reaction leads to positive entropy change:

• A) CaO(s) + CO₂(g) → CaCO₃(s): The reaction produces a solid from a solid and a gas, reducing the number of gas molecules and therefore it is expected to have a negative entropy change.
• B) 2SO₃(g) → 2SO₂(g) + O₂(g): The number of gas molecules increases from 2 to 3, hence this reaction would have a positive entropy change.
• C) N₂(g) + 3H₂(g) → 2NH₃(g): Here, the number of gas molecules decreases from 4 to 2, indicating a negative entropy change.
• D) H₂O(l) → H₂O(s): This is a phase change from liquid to solid, which usually results in a decrease in entropy, and thus negative entropy change.
• E) Ag+(aq) + Cl-(aq) → AgCl(s): Formation of a solid AgCl from ions in solution decreases the dispersal of matter, leading to negative entropy change.

Hence, the reaction with a positive entropy change is B) 2SO₃(g) → 2SO₂(g) + O₂(g).