Calculate the volume occupied by $4.045\times {10}^{23}$ molecules of oxygen at ${27}^{\circ }C$ and having a pressure of $700torr$.

No. of moles ${}^{\prime }{n}^{\prime }=\frac{4.045\times {10}^{23}}{6.023\times {10}^{23}}=0.672$

$P=\frac{700}{760}atm$
Now using the gas equation, $PV=nRT$
=$\frac{700}{760}V=0.672\times 0.0821\times 300$

$⟹V=17.97d{m}^3$