Chemical Kinetics - Result Question 40
####40. The reaction $A \to B$ follows first order kinetics. The time taken for 0.8 mole of $A$ to produce 0.6 mole of $B$ is 1 hour. What is the time taken for conversion of 0.9 mole of $A$ to produce 0.675 mole of $B$ ?
(a) 2 hours
(b) 1 hour
(c) 0.5 hour
(d) 0.25 hour
[2003]
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Solution:
- (b) $A \to B$ For a first order reaction given $a=0.8 mol, \quad(a-x)=0.8-0.6=0.2$
$ k=\frac{2.303}{1} \log \frac{0.8}{0.2} \text{ or } k=2.303 \log 4 $
again $a=0.9, a-x=0.9-0.675=0.225$
$ k=\frac{2.303}{t} \log \frac{0.9}{0.225} $
$2.303 \log 4=\frac{2.303}{t} \log 4$
Hence $t=1$ hour
