Summation of molecularity and order of reaction may be:

The reaction of hydrogen and iodine monochloride is given as:

${\mathrm{H}}_{2 \left(\mathrm{g}\right)}+2{\mathrm{ICl}}_{ \left(\mathrm{g}\right)}⟶2{\mathrm{HCl}}_{ \left(\mathrm{g}\right)}+{\mathrm{I}}_{2 \left(\mathrm{g}\right)}$

The reaction is of a first-order, with respect to ${\mathrm{H}}_{2 \left(\mathrm{g}\right)}$ and ${\mathrm{ICl}}_{ \left(\mathrm{g}\right)},$ following mechanisms were proposed.

Mechanism $\mathrm{A}:$

${\mathrm{H}}_{2 \left(\mathrm{g}\right)}+2\mathrm{ICl}{ }_{\left(\mathrm{g}\right)}⟶2{\mathrm{HCl}}_{ \left(\mathrm{g}\right)}+{\mathrm{I}}_{2 \left(\mathrm{g}\right)}$

Mechanism $\mathrm{B}:$

${\mathrm{H}}_{2 \left(\mathrm{g}\right)}+{\mathrm{ICl}}_{ \left(\mathrm{g}\right)}⟶{\mathrm{HI}}_{ \left(\mathrm{g}\right)};$ slow

$\mathrm{HI}{ }_{\left(\mathrm{g}\right)}+{\mathrm{ICl}}_{ \left(\mathrm{g}\right)}⟶\mathrm{HCl}{ }_{\left(\mathrm{g}\right)}+{\mathrm{I}}_{2 \left(\mathrm{g}\right)};$ fast

Which of the above mechanism(s) can be consistent with the given information about the reaction?

The bromination of acetone that occurs in acid solution is represented by the equation ${\mathrm{CH}}_3{\mathrm{COCH}}_3\left(\mathrm{aq}\right)+{\mathrm{Br}}_2\left(\mathrm{aq}\right)\to {\mathrm{CH}}_3{\mathrm{COCH}}_2\mathrm{Br}\left(\mathrm{aq}\right)+{\mathrm{H}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Br}}^{-}\left(\mathrm{aq}\right)$
These kinetic data were obtained for given reaction concentrations.
                                   Initial concentrations, $\mathrm{M}$

                          Initial Rate, disappearance of ${\mathrm{Br}}_2, \mathrm{M} {\mathrm{s}}^{-1}$
                                             $$\begin{gathered} 5.7\times {10}^{-5} \\ 5.7\times {10}^{-5} \\ 1.2\times {10}^{-4} \\ 3.1\times {10}^{-4} \end{gathered}$$                     

Based on these data, the rate of reaction is :