$p V^{2}=\beta$  ................$(i)$

As gas is ideal, it obeys gas equation,

$p V=n R T$    .................$(ii)$

From Eqs. $(i)$ and $(ii)$, gives

$\left(n R^{\prime} T\right) \cdot V=\beta$

Here, $n=0.02\, moles$,

$R=8.31 \,JK ^{-1} mol ^{-1}$,

$T=20^{\circ} C +273=293 \,K$

and $V=1500 \,cm ^{3}=1.5 \times 10^{-3} \,m ^{3}$

$\therefore \quad \beta=0.02 \times 8.31 \times 293 \times 1.5 \times 10^{-3}$

$=7.3 \times 10^{-2} \,Pa - m ^{6}$

$\approx 7.5 \times 10^{-2} \,Pa \cdot m ^{6}$