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JEE Main · 2024 · 06 Apr 2024 · Shift 2 · Chemical Thermodynamics

For the reaction at

298 K

,

2 A + B \to C

.

Δ H = 400 kJ mol^{- 1}

and

Δ S = 0.2 kJ mol^{- 1} K^{- 1}

. The reaction will become spontaneous above ______ K.

Answer: 2000

Solution

At the threshold of spontaneity,

Δ G = 0 = Δ H - T Δ S

, so

T = \frac{Δ H}{Δ S} = \frac{400}{0.2} = 2000

K. Since

Δ H > 0

and

Δ S > 0

,

Δ G

turns negative (spontaneous) only above this temperature.

JEE Main · 2024 · 06 Apr 2024 · Shift 2 · Integer answer

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