Question

Determine the time required to 75% complete the first order reaction.If the reaction 20% complete in 10 min. Choose tha correct options​

Answer 1

Explanation:

From 20 % completion

$k \: = \frac{2.303}{t} log( \frac{a}{a - x} )$

$k \: = \frac{2.303}{10} log( \frac{100}{80} )$

$k \: = \frac{2.303}{10} log( \frac{5}{4} )$

$k \: = \frac{2.303}{10} log(5) - log(4)$

$k \: = \frac{2.303}{10} (0.698 - 0.602)$

$k \: = \frac{2.303 \times 0.096}{10}$

$k \: = 0.0221$

• Now for 75% completion

$t \: = \frac{2.303}{k} log( \frac{a}{a - x} )$

$t \: = \frac{2.303}{0.0211} log( \frac{100}{25} )$

$t \: = \frac{2.303}{0.0221} log(4)$

$t \: = 104.2 \times 0.602$

$t \: = 62.72 \: \: minutes$