$z=1+\frac{BP}{RT}=>lnQ=\frac{BP}{RT}.$

$($b$)$ Assume the mixing rule $\frac{?}{\text{b}\text{a}\text{r}}(B)=\frac{B_1{B}_{27}}{B_{2x}{x}_1+B_4{x}_x}$ for a binary mixiute. Derjes an expression for

$n_n$hat$(p{)}_1=\frac{(nhn)}{(hat(i)){}_i}$