Consider the possible reaction mechanism below.

Question

A + B ➞ C + D

D + B ➞ C

a. Show that mechanism is consistent with balanced equation.

b. Show which is the rate-determining step (RDS). Explain your choice.

Answer 1

The balanced equation isn't provided, only the elementary steps of the mechanism. If we assume the balanced equation is

A + 2B ==> 2C , then ...

(a). Showing the following mechanisms is consistent:

A + B ==> C + D

D + B ==> C

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A + D + 2B ==> 2C + D

A + 2B ==> 2C

(b). The RDS would have to be the first step of A + B ==> C + D. The reason for this is that D is an intermediate since it is produced in the first step, and then used in the second step. Thus the rate of production of D will regulate the rate of production of C