The gas phase decomposition of dinitrogen pentoxide at 335 K

Question

N2O5(g) 2 NO2(g) + ½ O2(g)

is first order in N2O5.

During one experiment it was found that when the initial concentration of N2O5 was 0.218 M, the concentration of N2O5 dropped to 2.96E-2 M after 282 s had passed.

Based on this experiment, the rate constant for the reaction is

Answer 1

rate = -delta [N2O5]/delta time
rate = (0.218-0.0296)/282 = ?
Then rate = k[A]. Calculate k.