N2O5→2NO2+21O2 At t=0 At t=50 min5050−p102p102p1 Total pressure at 50 minutes $\begin{aligned}
&=50-\mathrm{p}_1+2 \mathrm{p}_1+\frac{\mathrm{p}_1}{2}=87.5 \
&50+\frac{3 \mathrm{p}_1}{2}=87.5 \
&\frac{3 \mathrm{p}_1}{2}=37.5 \
&\therefore \quad \mathrm{p}_1=\frac{37.5 \times 2}{3}=25
\end{aligned}At\mathrm{t}=100 \mathrm{min} \quad 50-\mathrm{p}_2 \quad 2 \mathrm{p}_2 \quad \frac{\mathrm{p}_2}{2}50minutesishalflifeperiodFor100minutesi.e.for2halflives50-p_2=12.5\therefore \mathrm{p}_2=37.5 \mathrm{mm} \text { of } \mathrm{Hg}Totalpressureat100minutes=50-\mathrm{p}_2+2 \mathrm{p}_2+\frac{\mathrm{p}_2}{2}=50+\frac{3 \mathrm{p}_2}{2}=50+\frac{3}{2} \times 37.5=50+56.25=106.25 \mathrm{~mm}of\mathrm{Hg}$