JEE Main 2025 Apr 4 Shift 1, Chemistry Q2: Gibbs Energy Change and Equilibrium

JEE Main2025Apr 4, Shift 1Chemistry

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 $T_{e}$ , then the reaction becomes spontaneous at :

A
$T = T_{e}$
B
$T_{e} > T$
C
$T > T_{e}$
D
$T_{e} = 5 T$

Solution

For spontaneity we need $Δ G < 0$ , i.e. $Δ H - T Δ S < 0$ .

With $Δ H > 0$ and $Δ S > 0$ , this rearranges to $T > \frac{Δ H}{Δ S}$ .

At equilibrium $Δ G = 0$ , which defines $T_{e} = \frac{Δ H}{Δ S}$ .

$∴$ The reaction is spontaneous when $T > T_{e}$ .

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JEE Main 2025 Apr 4 Shift 1, Chemistry Q2: Gibbs Energy Change and Equilibrium

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