Question

In which of the following reactions, standard entropy change (\( \Delta S^\circ \)) is positive and standard Gibbs’s energy change (\( \Delta G^\circ \)) decreases sharply with increasing temperature?

• A. \( C(g) + \frac{1}{2} O_2(g) \to CO(g) \)
• B. \( CO(g) + \frac{1}{2} O_2(g) \to CO_2(g) \)
• C. \( Mg(s) + \frac{1}{2} O_2(g) \to MgO(s) \)
• D. \( \frac{1}{2} C(graphite) + \frac{1}{2} O_2(g) \to \frac{1}{2} CO_2(g) \)

Hint:

Reactions with a positive entropy change become more favorable at higher temperatures.

Answer 1

The Correct Option is A

Step 1: Entropy change and Gibbs’s energy.
In reactions where entropy increases, the reaction becomes more favorable at higher temperatures, leading to a negative \( \Delta G \). The reaction where carbon (graphite) reacts to form CO has a positive entropy change.
Thus, the correct answer is (1).