AIPMT PRELIMS2005Chemistry-Chemical Kinetics

AIPMT PRELIMS 2005 Chemistry First Order Reactions MCQ Question

Type: MCQ-numerical-Medium-Class 12

For a first order reaction A → B, the reaction rate at reactant concentration of 0.01 M is found to be 2.0 × 10⁻⁵ mol L⁻¹ s⁻¹. The half life period of the reaction is:

A

227 s

B

327 s

C

527 s

D

347 s

Correct Answer

Option D

Detailed Explanation

The half-life of a first-order reaction is given by t₁/₂ = 0.693/k. The rate constant k can be calculated using the rate equation: rate = k[A]. Substituting the given values, k = 2.0 × 10⁻⁵ / 0.01 = 2.0 × 10⁻³ s⁻¹. Therefore, t₁/₂ = 0.693 / 2.0 × 10⁻³ = 346.5 s, approximately 347 s.

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