For the decomposition reaction AB → A + B, the experimentally determined rate law was found to be: rate = k[AB]2 , and k = 0.20 L/mol•s. How long will it take for AB to reach one third of its initial concentration of 1.50 M? (

It would take 20 seconds

Explanation:

Let the final concentration of AB be C

Rate = k[C]^2 = change in concentration of AB/time

k is the rate constant = 0.2 L/mol.s

Initial concentration of AB = 1.5 M

Final concentration of AB = 1/3 × 1.5 = 0.5 M

Change in concentration of AB = 1.5 - 0.5 = 1 M

0.2 × 0.5^2 = 1/time

time = 1/0.05 = 20 s