Solved: CHEMISTRY Question for NEET

NEET CHEMISTRYMedium

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:

$t = 0.693/k$

$t = 6.909/k$

$t = 4.606/k$

$t = 2.303/k$

Step-by-Step Solution

First order rate constant is given as, $k = \frac{2.303}{t} \log \frac{[A_0]}{[A]_t}$ . For 99% completed reaction, $k = \frac{2.303}{t} \log \frac{100}{1} = \frac{2.303}{t} \log 10^2 = \frac{2.303}{t} \times 2 \log 10$ . $t = \frac{2.303}{k} \times 2 = \frac{4.606}{k}$ .

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