Consider the hypothetical reaction 2 A + B → 2 C + D. The following two-step mechanism is proposed for the reaction:

Step 1: A + B → C + X

Step 2: A + X → C + D

X is an unstable intermediate.

(a) What is the predicted rate law expression if Step 1 is rate determining?

(b) What is the predicted rate law expression if Step 2 is rate determining?

(c) Your result for part (b) might be considered surprising for which of the following reasons: (i) The concentration of a product is in the rate law. (ii) There is a negative reaction order in the rate law. (iii) Both reasons (i) and (ii). (iv) Neither reasons (i) nor (ii).