The molar heat capacities of A, B and C are in the ratio 1:2:3. The enthalpy change for the reaction A + B → C at temperature T1 is ΔH1. Assuming that the heat capacities do not change with temperatur

Question

The molar heat capacities of A, B and C are in the ratio 1:2:3. The enthalpy change for the reaction A + B → C at temperature T1 is ΔH1. Assuming that the heat capacities do not change with temperature, the enthalpy change, Δ$H_2$, at temperature, T2 (T2 > T1) will be

Prashant Kotian · Accepted Answer

Correct answer: B. According to Kirchhoff's Equation: Δ - ΔH1 = ΔCp × (T2 - T1). Here, ΔCp for the reaction A + B → C is given by: ΔCp = (C) - [(A) + (B)]. Since the ratio of molar heat capacities is 1:2:3, we can write (A) = x, (B) = 2x, and (C) = 3x. Thus, ΔCp = 3x - (x + 2x) = 0. Since ΔCp = 0, Δ - ΔH1 = 0, which means Δ = ΔH1.

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