Question

The rate of a reaction doubles when concentration of reactant is doubled. The order of reaction is:

• A. Zero order
• B. First order
• C. Second order
• D. Third order

Hint:

If doubling concentration doubles rate, the reaction is first order. If rate becomes four times, it is second order.

Answer 1

The Correct Option is B

Concept: For a reaction: \[ Rate = k[A]^n \] where \( n \) is the order of reaction.

Step 1: Writing the rate law.
Suppose initial rate is: \[ R_1 = k[A]^n \] When concentration is doubled: \[ R_2 = k(2[A])^n \] \[ R_2 = 2^n k[A]^n \] \[ R_2 = 2^n R_1 \]

Step 2: Using given condition.
The rate doubles: \[ R_2 = 2R_1 \] Thus: \[ 2^n R_1 = 2R_1 \] \[ 2^n = 2 \] \[ n = 1 \]

Step 3: Final conclusion.
The reaction is first order. \[ \boxed{\text{First order}} \]