Chapter 12, Problem 50E

The decomposition of hydrogen iodide on finely divided gold at 150°C is zero order with respect to HI. The rate defined below is constant at 1.20 × 10⁻⁴ mol/L · s.

$\begin{array}{l}\text{2HI}\left(g\right)\stackrel{\text{Au}}{\to }{\text{H}}_2\left(g\right)+{\text{I}}_{\text{2}}\left(g\right)\\ \text{Rate}=-\frac{\Delta \left[\text{HI}\right]}{\Delta t}=k=1.20\times {10}^{-4}\text{mol/L}\cdot \text{s}\end{array}$

a. If the initial HI concentration was 0.250 mol/L, calculate the concentration of HI at 25 minutes after the start of the reaction.

b. How long will it take for all of the 0.250 M HI to decompose?