Question

Choose the correct option regarding a complex reaction:

• A. It is a reaction that proceeds in more than two steps or follows some mechanism.
• B. Order of a complex reaction is not defined.
• C. Molecularity of a complex reaction is fractional
• D. All of the above.

Answer 1

The correct option is A It is a reaction that proceeds in more than two steps or follows some mechanism.

Complex Reaction
Reaction that proceeds in more than two steps or follow some mechanism.As it consists of multiple steps,every step behaves as an elementary reaction.So, each step has its own molecularity

$A\to \text{Intermediate}\to P$


Example: For the complex reaction,
$2NO+2H_2\to N_2+2H_{2}O$
Steps:

1. $2NO\rightleftharpoons N_2{O}_2$
2. $N_2{O}_2+H_2\to N_{2}O+H_{2}O$
3. $N_{2}O+H_2\to N_2+H_{2}O$

Order of a complex reaction can be determined by determining its mechanism, generally using the rate determining step.