Let us consider a reversible reaction at temperature, T. In this reaction, both $\Delta \mathrm{H}$ and $\Delta \mathrm{S}$ were observed to have positive values. If the equilibrium temperature is Te, then the reaction becomes spontaneous at:

(D) $\mathrm{Te}=5 \mathrm{~T}$

JEE Main · 2025 · 04 Apr 2025 · Shift 1 · Chemical Thermodynamics

Let us consider a reversible reaction at temperature, T.

In this reaction, both

Δ H

and

Δ S

were observed to have positive values. If the equilibrium temperature is Te, then the reaction becomes spontaneous at:

Answer: (C)

Spontaneity requires

Δ G = Δ H - T Δ S < 0

. With both

Δ H

and

Δ S

positive this is satisfied only when

T Δ S > Δ H

, that is

T > \frac{Δ H}{Δ S}

. At equilibrium

Δ G = 0

gives

T_{e} = \frac{Δ H}{Δ S}

, so the reaction becomes spontaneous when

T > T_{e}

JEE Main · 2025 · 04 Apr 2025 · Shift 1 · Single correct option