1.Suppose reaction 2B X has catalyst C, and rate = k[B] 2 [C]. Define catalyst.

ID: 952981 • Letter: 1

Question

1.Suppose reaction 2B X has catalyst C, and rate = k[B]2[C]. Define catalyst.

Explain how the catalyst is in the mechanism, yet cancels out of the net chemical equation.

How does the catalyst affect the activation energy?

2.Review Example 13.12. Suppose the reaction in problem 1 has the following mechanism:

2B B2 (fast equilibrium, rate constants are k1 forward and k-1 reverse)

B2 + C à B2C (slow, rate constants is k2)

B2C à X + C (fast, rate constants is k3)

Show how to derive rate = k[B]2[C]. First, use the equilibrium step to solve for [B2].

Then, substitute that for [B2] in the rate law from the rate-determining step.

How does the catalyst affect the activation energy?

A catalyst provides an alternative route for the reaction with lower activation energy.

Slowest step in reaction is (slow, rate constant k2) so rate = k2 [B]2[C]

so B2= (r/k2c)^1/2

Then we can substitute in above equation:

r =k2((r/k2c)^1/2)(C)

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