Question

For a given reaction, Δ H = 35.5kJ mol⁻1 and Δ S = 83.6J K⁻1mol⁻1. The reaction is spontaneous at (Assume that Δ H and Δ S do not vary with temperature)

• A. T > 425K
• B. All temperatures
• C. T > 298K
• D. T < 425K

Hint:

If Δ H > 0 and Δ S > 0, reaction is spontaneous only at high temperatures.

Answer 1

The Correct Option is A

Step 1: Gibbs free energy: Δ G = Δ H - TΔ S Step 2: Convert Δ S to kJ: Δ S = 0.0836kJ K⁻1mol⁻1 Step 3: For spontaneity, Δ G < 0: T > (Δ H)/(Δ S) = (35.5)/(0.0836) ≈ 425K