Q69 / 180 · NEET 2019 (All India) · Chemistry

If the rate constant for a first order reaction is $k$ , the time $(t)$ required for the completion of $99 %$ of the reaction is given by

A
$t = 0.693 / k$
B
$t = 6.909 / k$
Correct answer
C
$t = 4.606 / k$
D
$t = 2.303 / k$

Solution

$k = \frac{2.303}{t} l o g \frac{a}{a - x}$

$a = 100$

$a - x = 100 - 99 = 1$

$k = \frac{2.303}{t} l o g \frac{100}{1}$

$t = \frac{4 .606}{k}$

Hence, the correct answer is option: 'C'.

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