Question

Identify the molecularity and order of the following elementary reaction, \(\text{C}_{2}\text{H}_{5}\text{I}_{(g)}\rightarrow \text{C}_{2}\text{H}_{4(g)}+\text{HI}_{(g)}\), if rate = \(k[\text{C}_{2}\text{H}_{5}\text{I}]\)

• A. Bimolecular and First-Order
• B. Unimolecular and First-Order
• C. Unimolecular and Second-order
• D. Bimolecular and second-order kinetics

Hint:

Count the molecules colliding in the single step for molecularity, and add the powers in the rate law for order.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
Molecularity is the number of reacting species that take part in an elementary step. Order is the sum of the powers of concentration terms in the rate law.

Step 2: Molecularity
Only one molecule of \(\text{C}_{2}\text{H}_{5}\text{I}\) breaks down in the step, so the reaction is unimolecular.

Step 3: Order
The rate law is \(\text{rate} = k[\text{C}_{2}\text{H}_{5}\text{I}]^{1}\), so the order is 1, which is first order.

Final Answer:
The reaction is unimolecular and first order. \[ \boxed{\text{(B) }\text{Unimolecular and First-Order}} \]