Chemistry - Thermochemistry Question with Solution | TestHub

Question Explanation: Calculating standard reaction enthalpy from the Van't Hoff equation.

Concept: Van't Hoff Equation

Solution:

Identify the slope term in the temperature-dependent equilibrium constant expression to find enthalpy. Van't Hoff Equation: In ${\mathrm{K}}_{\mathrm{p}}=-\frac{\Delta {\mathrm{H}}^{\circ }}{\mathrm{RT}}+\ln {\mathrm{K}}_{\mathrm{p}}=-\frac{\Delta {\mathrm{H}}^{\circ }}{\mathrm{RT}}+$ I Comparing with $\ln {\mathrm{K}}_{\mathrm{p}}=3-\frac{2000}{\mathrm{T}}:\frac{\Delta {\mathrm{H}}^{\circ }}{\mathrm{R}}=2000$ $\Rightarrow \Delta {\mathrm{H}}^{\circ }=2000\times \mathrm{R}\Delta {\mathrm{H}}^{\circ }=2000\times 2\mathrm{cal}/\mathrm{mol}-\mathrm{K}=4000\mathrm{cal}/\mathrm{mol}=4\mathrm{kcal}/\mathrm{mol}$.

Final Answer: $4\mathrm{kcal}{\mathrm{mol}}^{-1}$