Question

Objectives: To be able to derive the necessary rate equations for multistep reactions using rate limiting cases and the steady-state approximation. Further we should be able to derive the necessary half-life equations based on 1st order rate kinetics.

Question 1. This is a consecutive reaction irreversible first-rate reactions below

A →B →C →....

12

<Suppose that

And you are interested in isolating the largest possible amount of B. Given the values of k1 and k2, derive an equation for the time that the concentration of B goes through the maximum. Now consider two cases: (a) A reacts more rapidly than B and (b) A reacts less rapidly than B. For a given value of k2, in which case would you wait the longer time for B to go through its maximum?

Hint: Start by writing out the differential equations for each step (i.e. d[A ]/dt = − k1[A ]). Then solve for [B]. 2 hint: [B] is maximum when d[B]/dt = 0

Answer 1