If pressure of  CO2 (real gas) in a container is given by P=RT2V−b−a4b2 then mass of the gas in container is

Vander wall's gas equation for μ mole of real gasP+μ2aV2(V−μb)=μRT⇒P=μRTV−μb−μ2aV2on comparing the given equation with this standard equation we get  μ=12. Hence μ=mM ⇒ mass of gas m=μm=12×44=22gm.