Which of the following is an elementary reaction?

Write about elementary and complex reactions.

Reaction : $2Br^{-} + H_2O_2 + 2H^{+} \to Br_2 + 2H_2O$
takes place in two steps :
$(a)$ $Br^{-} + H^{+} + H_2O_2 \xrightarrow{slow} HOBr + H_2O$
$(b)$ $HOBr + Br^{-} + H^{+} \xrightarrow{fast} H_2O + Br_2$
The order of the reaction is

For the reaction $2NOBr(g) \rightarrow 2NO(g) + Br_2(g)$, the rate law is $r = k[NOBr]^2$. If the rate constant $k = 1.62 \text{ M}^{-1} \text{ s}^{-1}$ and the concentration of $NOBr$ is $5 \times 10^{-3} \text{ M}$, what is the rate of the reaction?

Select the rate law that corresponds to the data shown for the following reaction $A + B \to C$

$Expt. \ No.$	$[A]$	$[B]$	$Initial \ Rate$
$1$	$0.012$	$0.035$	$0.10$
$2$	$0.024$	$0.070$	$0.80$
$3$	$0.024$	$0.035$	$0.10$
$4$	$0.012$	$0.070$	$0.80$

The experimental data for the reaction $2A + B_2 \to 2AB$ is given below. Determine the rate equation for the reaction.

$Exp.$	$[A]_0$	$[B_2]_0$	$Rate \ (mol \ L^{-1} \ s^{-1})$
$(1)$	$0.50$	$0.50$	$1.6 \times 10^{-4}$
$(2)$	$0.50$	$1.00$	$3.2 \times 10^{-4}$
$(3)$	$1.00$	$1.00$	$3.2 \times 10^{-4}$