Rate of disappearance of the reactant 'A' in the reversible reaction: A ⇌ B, at two temperatures is given as
-d[A]/dt = (2.0 × 10⁻³ s⁻¹) [A] - (5.0 × 10⁻⁴ s⁻¹) [B] (at 27°C)
-d[A]/dt = (8.0 × 10

Question

Rate of disappearance of the reactant 'A' in the reversible reaction: A ⇌ B, at two temperatures is given as
-d[A]/dt = (2.0 × 10⁻³ s⁻¹) [A] - (5.0 × 10⁻⁴ s⁻¹) [B] (at 27°C)
-d[A]/dt = (8.0 × 10⁻² s⁻¹) [A] - (4.0 × 10⁻³ s⁻¹) [B] (at 127°C)
The enthalpy of reaction in the given temperature range is

Prashant Kotian · Accepted Answer

Correct answer: D. K₁ (at 300K) = k_f / k_b = (2.0 × 10⁻³) / (5.0 × 10⁻⁴) = 4. K₂ (at 400K) = (8.0 × 10⁻²) / (4.0 × 10⁻³) = 20. Using van't Hoff equation: log(K₂/K₁) = (ΔH / 2.303 R) (1/T₁ - 1/T₂). log(20/4) = log(5) = (ΔH / (2.303 × 8.314)) (100 / (300 × 400)). Solving for ΔH gives ΔH = [2.303 × 8.314 × 300 × 400 / 100] · log(5) J/mol. Therefore, correct answer is D.

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