The reaction 2no2 ? 2no + o2 follows second-order kinetics. at 300 °c, [no2] drops from 0.0100 m to 0.00650 m in 100.0 s. the rate constant for the reaction is m-1s-1.

For a second order kinetics, the reaction rate expression would be

-r = -dCa / dt = kCa^2    where k is the reaction constant and Ca is the concentration of reactant A.

Integrating this from Cao to Caf, will have the expression,

1/Caf - 1/Cao = kt

Substituting the given values and calculating for k,

1/0.00650 - 1/0.0100 = k(100)
k = 0.538 / M-s