Question

Which of the following is an elementary reaction ?

• A. \(\text{O}_{3(g)}\rightarrow \text{O}_{2(g)}+\text{O}_{(g)}\)
• B. \(2\text{NO}_2\text{Cl}_{(g)}\rightarrow 2\text{NO}_{2(g)}+\text{Cl}_{2(g)}\)
• C. \(2\text{NO}_{2(g)}+\text{F}_{2(g)}\rightarrow 2\text{NO}_2\text{F}_{(g)}\)
• D. \(2\text{NO}_{(g)}+\text{Cl}_{2(g)}\rightarrow 2\text{NOCl}_{(g)}\)

Hint:

An elementary reaction occurs in a single step; its molecularity is small and equals the number of reacting species.

Answer 1

The Correct Option is A

Step 1: Test:
A reaction is elementary only if the balanced equation itself shows what really collides. Look for the simplest equation.

Step 2: Apply:
Ozone splitting into $\text{O}_2$ and an O atom has one reactant molecule and one bond-breaking event. The other equations carry stoichiometric coefficients of 2, and their rate laws are known from experiment to be of the complex type.

Step 3: Answer:
Option (A).

Final Answer:
Option (A). \[ \boxed{\text{(A) } \text{O}_{3(g)}\rightarrow \text{O}_{2(g)}+\text{O}_{(g)}} \]