Chemistry - Chemical Kinetics Question with Solution | TestHub

According to the question,
${\mathrm{p}}_0-\mathrm{p}+\mathrm{p}=120$mm
or${\mathrm{p}}_0+\mathrm{p}=120$mm
or$\mathrm{p}=120-80=40$mm.
For a first order reaction,
$\mathrm{k}=\frac{1}{\mathrm{t}}\ln \frac{{\mathrm{p}}_0}{{\mathrm{p}}_0-\mathrm{p}}=\frac{1}{20}\ln \frac{80}{80-40}=\frac{1}{20}\ln 2$…(i)
But we know that${\mathrm{t}}_{\frac{1}{2}}=\frac{1\mathrm{n}2}{\mathrm{k}}$…(ii)
From equations (i) and (ii)
$\mathrm{k}=\frac{1}{20}\mathrm{k}{\mathrm{t}}_{\frac{1}{2}}$
${\mathrm{t}}_{\frac{1}{2}}=20$min.