Question

I2 => 2 I I + H2 => H2I H2I + I => 2 HI What is the molecularity of step 2? A. unimolecular B. bimolecular C. termolecular D. impossible to tell without knowing which is the slow step

Answer 1

Answer : The correct option is, (B) bimolecular

Explanation :

Molecularity : It is defined as the total number of reactant molecules taking part in the balanced equation of a reaction. It is a theoretical concept.

The given chemical reaction are,

Step (1) : $I_2\rightarrow 2I$

Step (2) : $I+H_2\rightarrow H_2I$

Step (3) : $H_2I+I\rightarrow 2HI$

The number of reactants molecules taking part in the balanced equation of a reaction 2 are, $I\text{ and }H_2$.

In this reaction, 1 'I' molecules reacts with the 1 $H_2$ molecule.

Total number of reactant molecule = 1 + 1 = 2

The molecularity of the reaction is 2 that means, the elementary reaction is bimolecular.

Hence, the correct option is, (B) bimolecular