(a) In an adiabatic process,
$pV^{\gamma} = constant$
$\Rightarrow \ \ \frac{p_{1}}{p_{2}} = \left( \frac{V_{2}}{V_{1}} \right)^{\gamma}$
$\Rightarrow \ \ \frac{p_{1}}{p_{2}} = \left( \frac{1}{8} \right)^{5/3}$
$\Rightarrow \ \ \frac{p_{1}}{p_{2}} = \left( \frac{1}{2^{3}} \right)^{5/3} = \frac{1}{32}$
$\therefore\ \frac{p_{2}}{p_{1}} = 32$