Which is the unit of the rate constant for a second-order reaction?

For a reaction,$K = 4.5 \times 10^{-4} \ L \ mol^{-1} \ s^{-1}$. What is the order of the reaction?

The unit of the rate constant for a second-order reaction is ....

The rate constant of the reaction,$2 H_2O_2 \rightarrow 2 H_2O + O_2$ is $3 \times 10^{-3} \ min^{-1}$. At what concentration of $H_2O_2$ will the rate of reaction be $2 \times 10^{-4} \ M \ s^{-1}$?

The following are the rate constants of two different reactions. What is the overall order of each reaction?
$(a)$ $2.1 \times 10^{-2} \ mol \ L^{-1} \ s^{-1}$
$(b)$ $4.5 \times 10^{-3} \ min^{-1}$

The possible mechanism for the reaction $2NO + Br_2 \to 2NOBr$ is:
$NO + Br_2 \rightleftharpoons NOBr_2$ (Fast)
$NOBr_2 + NO \to 2NOBr$ (Slow)
The rate law expression is: