Examveda

The half life period of a first order reaction is

A. Always the same irrespective of the reaction

B. Dependent on initial concentration of the reactants

C. Proportional to the initial concentration of reactants

D. Half the specific rate constant

Answer: Option A

Solution (By Examveda Team)

Option A: Always the same irrespective of the reaction

This option suggests that the half-life period of a first-order reaction is always the same regardless of the reaction. This statement is correct. For a first-order reaction, the half-life period (t₁/₂) is constant and does not depend on the initial concentration of the reactants.

Option B: Dependent on initial concentration of the reactants

This option suggests that the half-life period of a first-order reaction depends on the initial concentration of the reactants. This statement is incorrect. The half-life of a first-order reaction is independent of the initial concentration and remains constant throughout the reaction.

Option C: Proportional to the initial concentration of reactants

This option suggests that the half-life period of a first-order reaction is proportional to the initial concentration of the reactants. This statement is incorrect. In a first-order reaction, the half-life is not proportional to the initial concentration; it remains constant regardless of the concentration.

Option D: Half the specific rate constant

This option suggests that the half-life period of a first-order reaction is half the specific rate constant. This statement is incorrect. The half-life of a first-order reaction is related to the rate constant (k) by the formula t₁/₂ = 0.693/k. It is not half the rate constant but rather a function of the rate constant.

Conclusion:

The correct answer is Option A: Always the same irrespective of the reaction because, for a first-order reaction, the half-life period is constant and does not depend on the initial concentration of the reactants.

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Comments (1)

  1. Devendra Khadipure
    Devendra Khadipure:
    1 year ago

    Half life of first order reaction is ln(2)/k ,half life is inversely proportional to k for first order reaction. And does not depend upon any concentration.

Related Questions on Chemical Reaction Engineering

A first order gaseous phase reaction is catalysed by a non-porous solid. The kinetic rate constant and the external mass transfer co-efficients are k and $${{\text{k}}_{\text{g}}}$$ respectively. The effective rate constant (keff) is given by

A. $${{\text{k}}_{\text{e}}}{\text{ff}} = {\text{k}} + {{\text{k}}_{\text{g}}}$$

B. $${{\text{k}}_{\text{e}}}{\text{ff}} = \frac{{{\text{k}} + {{\text{k}}_{\text{g}}}}}{2}$$

C. $${{\text{k}}_{\text{e}}}{\text{ff}} = {\left( {{\text{k}}{{\text{k}}_{\text{g}}}} \right)^{\frac{1}{2}}}$$

D. $$\frac{1}{{{{\text{k}}_{\text{e}}}{\text{ff}}}} = \frac{1}{{\text{k}}} + \frac{1}{{{{\text{k}}_{\text{g}}}}}$$