The following data were collected in two studies of the reaction 2A + B †’ C + D where

In experiment 1, [B] 0 = 5.0 M. In experiment 2, [B] 0 = 10.0 M.
a. Why is [B] much greater than [A]?
b. Give the rate law and value for k for this reaction.
c. Which of the following mechanisms could be correct for this reaction? Justify your choice.
i. A + B ‡Œ E (fast equilibrium)
E + B †’ C + D (slow)
ii. A + B ‡Œ E (fast equilibrium)
E + A †’ C + D (slow)
iii. A + A †’ E (slow)
E + B †’ C + D (fast)

Rate-_ xperiment 1 (M)X 10 Experiment 2 AJ (M)x 10-2 Time (s 20. 40. 60. 80. 100. 120. 10.0 6.67 5,00 4.00 3.33 2.86 2.50 10.0 5.00 3.33 2.50 2.00 1.67 1.43