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← JEE Main 2026 · 5 Apr · Shift 1
ChemistryInteger+4 / -1Question 74 of 75

JEE Main 2026 · 5 Apr · Shift 1, Chemistry question 74

The values of pressure equilibrium constant recorded at different temperatures for the following equilibrium reaction have been given below

A(g)⇌B(g)+C(g)\ce{A(g) <=> B(g) + C(g)}

1T\frac{1}{T} (K−1^{-1}) log⁡10Kp\log_{10} K_p
0.05 3.5
0.06 2.5
0.07 1.5

The magnitude of ΔH∘R\frac{\Delta H^\circ}{R} calculated from the above data is ________. (Nearest integer)

Answer and worked solution

Official answer: 230

van 't Hoff.
log⁡10Kp=−ΔH∘2.303R⋅1T+const.\log_{10}K_p=-\frac{\Delta H^\circ}{2.303R}\cdot\frac1T+\text{const}.

Slope of the data: 1.5−3.50.07−0.05=−100\dfrac{1.5-3.5}{0.07-0.05}=-100.

So ΔH∘R=2.303×100=230.3\dfrac{\Delta H^\circ}R=2.303\times100=230.3.

Answer: 230