Assertion (A): In a first-order reaction, the time required to reduce the reactant concentration from 0.8 M to 0.4 M is exactly the same as the time required to reduce it from 0.4 M to 0.2 M . Reason (R): The half-life

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Correct answer: A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

For a first-order reaction, the time required to reduce the concentration of the reactant to half of its initial value is called the half-life, denoted by

t_{1/2}

.

The reduction from

0.8 \text{ M}

to

0.4 \text{ M}

represents one half-life. Similarly, the reduction from

0.4 \text{ M}

to

0.2 \text{ M}

also represents one half-life.

The half-life of a first-order reaction is given by the expression

t_{1/2} = \dfrac{0.693}{k}

.

This expression shows that the half-life is independent of the initial concentration of the reactant. Therefore, the time taken for both reductions is exactly the same.

Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).

Answer: Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

Assertion (A): In a first-order reaction, the time required to...

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