The rate constant of which of the following reactions is independent of the concentration of the reactants?

For the reaction $NO_2 + CO \rightarrow CO_2 + NO$,the rate law is given as $\text{Rate} = K [NO_2]^2$. What is the number of $CO$ molecules participating in the slow step?

For the reaction $A + 2B \to C$,the rate equation is given as $\text{Rate} = K[A][B]$. If the concentration of $A$ is kept constant but that of $B$ is doubled,what will happen to the rate of the reaction?

$A_2 + B_2 \to 2AB$; $R.O.R = k[A_2]^a[B_2]^b$

Initial $[A_2]$	Initial $[B_2]$	$R.O.R. (r) \ M s^{-1}$
$0.2$	$0.2$	$0.04$
$0.1$	$0.4$	$0.04$
$0.2$	$0.4$	$0.08$

Order of reaction with respect to $A_2$ and $B_2$ are respectively:

For the reaction $2A + B \rightarrow A_2B$,if the concentration of reactant $A$ is doubled and the concentration of reactant $B$ is halved,the rate of the reaction will:

If the rate constant $k = 4.5 \times 10^{-7} \text{ L}^2 \text{ mol}^{-2} \text{ s}^{-1}$, then what is the order of the reaction?