Question

At 30ºC, the half life for the decomposition of $AB_2$ is 200 s and is independent of the initial concentration of $AB_2$. The time required for 80% of the $AB_2$ to decompose is(Given : $log\; 2 = 0.30,\; log \;3 = 0.48$)

• A. 200 s
• B. 323 s
• C. 467 s
• D. 532 s

Answer 1

Answer: (C)

467 s

Answer 2

Since, half life is independent of the initial concentration of $AB_2$.

Hence, reaction is “First Order”.

$k =\frac{ 2.303 log\;2}{t_{1/2}}$

$\frac{2.303 log\;2}{t_{1/2}} = \frac{2.303}{t} \log\frac{100}{(100−80)}$

$\frac{2.303 \times 0.3 }{200} = \frac{2.303 }{ t }\log5$

$t = 467 \;s$