The equations for two reactions are shown.

$reaction{\text{ }}X\,\,\,2NOBr \to 2NO + B{r_2}$

$reaction{\text{ }}Y\,\,\,2NOCl \to 2NO + C{l_2}$

The two reactions have similar reaction mechanisms. 

The initial rate of reaction X is greater than that of reaction Y when measured under identical
conditions of temperature, pressure and reactant concentration.

Which statements explain this difference? 

1  The activation energy for reaction X is less than that of reaction Y.

2  The Br−Br bond is weaker than the Cl−Cl bond.

3  A higher frequency of collisions between molecules of NOBr occur than between molecules of NOCl .