Question

Assertion :For a first order reaction, $t_{1/2}$ is independent of the initial concentration of reactants. Reason: For a first order reaction, $t_{1/2}$ is thrice the $t_{7/8}$.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Assertion is true because
$t_{{}_2^{/}}=\frac{0.693}{K}$ is independent of initial concentration
Reason is also true
$t_{718}=3t_{{}^1{/}_2}$
$t_{718}=\frac{1}{K}ln\left[\frac{a}{a-\frac{79}{3}}\right]$
$=\frac{3ln2}{K}=\frac{3\times 0.693}{K}$
(R) also true but It is not correct explanation
to (A)
[B]