Kinetic experiments for the hydrogen–iodine reaction at give the rate law

CHEMISTRY · Subjective · A Level · Chemistry · Rate equations · Rate equations

Problem

Kinetic experiments for the hydrogen–iodine reaction at 450 ∘C450\,^{\circ}\text{C} give the rate law rate=k[H2][I2]rate = k[\text{H}_2][\text{I}_2]. Consider the following two proposed mechanisms (overall reaction H2+I2→2 HI\text{H}_2 + \text{I}_2 \to 2\,\text{HI}): Mechanism A Step 1 (slow): H2+I2→2 HI\text{H}_2 + \text{I}_2 \to 2\,\text{HI} Mechanism B Step 1 (slow): I2→2 I\text{I}_2 \to 2\,\text{I} Step 2 (fast): I+H2→HI+H\text{I} + \text{H}_2 \to \text{HI} + \text{H} Step 3 (fast): H+I2→HI+I\text{H} + \text{I}_2 \to \text{HI} + \text{I} Which mechanism, A or B, is consistent with the experimental rate law?

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