The rate constant is 0.556 L mol-1 s-1 at some temperature. If the initial concentration of NOBr in the container is 0.32 M, how long will it take for the concentration to decrease to 0.039 M

12.96 seconds

Explanation:

Assuming the reaction follows a first order

Rate = K[NOBr] = change in concentration of NOBr/time

K = 0.556 L mol^-1 s^-1

Change in concentration of NOBr = 0.32M - 0.039M = 0.281M

0.281/t = 0.556*0.039

t = 0.281/0.021684 = 12.96 seconds