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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3td164

A reaction has $Δ H = + 66.0 kJ mo l^{- 1}$ and $Δ S = + 110 J mo l^{- 1} K^{- 1}$ , both temperature independent. Select the correct statement(s).

AThe reaction is non-spontaneous at $298 K$ .
BThe reaction becomes spontaneous above $600 K$ .
C $Δ G$ at $700 K$ is $+ 11.0 kJ mo l^{- 1}$ .
DThe equilibrium constant $K$ exceeds $1$ at $650 K$ .

Answer: A, B, D

Δ G = Δ H - T Δ S = 66000 - 110 T

(J). At

298 K

,

Δ G = + 33.2 kJ

(non-spontaneous).

Δ G = 0

at

T = 66000/110 = 600 K

, so the reaction is spontaneous above it. At

700 K

,

Δ G = - 11.0 kJ

, negative, so statement 3 is false. At

650 K

,

Δ G = - 5.5 kJ < 0

, so

K > 1

.

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