Consider the reaction between iodine and hydrogen to form hydrogen iodide. Here are two possible mechanisms: I2 ⇌ 2 I. fast (rate constants k1, k−1) I + H2 ⇌ H2I fast (rate constants k2, k−2) H2I + I → 2HI. slow (rate constant k3) I2 ⇌ 2 I (rate constants k1, k−1) I+H2 →HI+H (rate constant k2) H+I2 →HI+I (rate constant k3) a. One of the mechanisms is a chain reaction. Choose which one, explain your reasoning, and identify in the mechanism the three stages (initiation, propagation, and termination) associated with such a reaction. b. Work out the rate law for the formation of HI using the first mechanism (mechanism i), noting all approximations you make. c. The reverse of the overall reaction between hydrogen and iodine is the decomposition of HI. The rate constant associated with this decomposition has a value of 1.2 x 10−3 L mol−1sec−1 at 700 K and 3.0 x 10−5 L mol−1sec−1 at 629 K. Find the activation energy for this decomposition process.
Consider the reaction between iodine and hydrogen to form hydrogen iodide. Here are two possible mechanisms:
I2 ⇌ 2 I. fast (rate constants k1, k−1)
I + H2 ⇌ H2I fast (rate constants k2, k−2)
H2I + I → 2HI. slow (rate constant k3)
I2 ⇌ 2 I (rate constants k1, k−1)
I+H2 →HI+H (rate constant k2)
H+I2 →HI+I (rate constant k3)
a. One of the mechanisms is a chain reaction. Choose which one, explain your reasoning, and identify in the mechanism the three stages (initiation, propagation, and termination) associated with such a reaction.
b. Work out the rate law for the formation of HI using the first mechanism (mechanism i), noting all approximations you make.
c. The reverse of the overall reaction between hydrogen and iodine is the decomposition of HI. The rate constant associated with this decomposition has a value of 1.2 x 10−3 L mol−1sec−1 at 700 K and 3.0 x 10−5 L mol−1sec−1 at 629 K. Find the activation energy for this decomposition process.
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