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 reactionThis 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)
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. $$\frac{1}{{{{\text{k}}_{\text{e}}}{\text{ff}}}} = \frac{1}{{\text{k}}} + \frac{1}{{{{\text{k}}_{\text{g}}}}}$$
The half life period of a first order reaction is given by (where, K = rate constant. )
A. 1.5 K
B. 2.5 K
C. $$\frac{{0.693}}{{\text{K}}}$$
D. 6.93 K
Catalyst is a substance, which __________ chemical reaction.
A. Increases the speed of a
B. Decreases the speed of a
C. Can either increase or decrease the speed of a
D. Alters the value of equilibrium constant in a reversible
A. $$ \propto {\text{CA}}$$
B. $$ \propto \frac{1}{{{\text{CA}}}}$$
C. Independent of temperature
D. None of these

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.