Chapter 11, Problem 99QAP

The gas-phase reaction between hydrogen and iodine ${\text{H}}_2\left(g\right)+{\text{I}}_2\rightleftharpoons 2\text{HI}\left(g\right)$proceeds with a rate constant for the forward reaction at 700°C of 138 L/moI $\cdot$

s and an activation energy of 165 kJ/moI.

(a) Calculate the activation energy of the reverse reaction given that $\Delta H_{\text{f}}°$ for HI is 26.48 kJ/moI and $\Delta H_{\text{f}}°$ for I₂(g) is 62.44 kJ/mol.

(b) Calculate the rate constant for the reverse reaction at 700°C. (Assume A in the equation $k={\text{Ae}}^{-E_a/RT}$ is the same for both forward and reverse reactions.)

(c) Calculate the rate of the reverse reaction if the concentration of HI is 0.200 M. The reverse reaction is second-order in HI.