Calculate the vapour pressure of a solution containing $\displaystyle 61$ g of benzoic acid (molar mass $\displaystyle =122 \mathrm{~g} \mathrm{~mol}^{-1}$ ) dissolved in $\displaystyle 500$ g of benzene when the vapour pressure of pure benzene at this temperature of experiment is $\displaystyle 66$ torr. Assume complete dimerization of benzoic acid in benzene.

𝑝$\displaystyle 1$° −𝑝$\displaystyle 1$ 𝑝$\displaystyle 1$ ° = 𝑖𝑥$\displaystyle 2$ = 𝑖 𝑤$\displaystyle 2$×𝑀$\displaystyle 1$ 𝑀$\displaystyle 2$×𝑤$\displaystyle 1$ $\displaystyle 66$−𝑝$\displaystyle 1$ = $\displaystyle 0.5$ × 𝑝$\displaystyle 1$ = $\displaystyle 63.4$𝑡𝑜𝑟𝑟 Alternate method 𝑝$\displaystyle 1$° −𝑝$\displaystyle 1$ 𝑝$\displaystyle 1$ ° = 𝑖𝑥$\displaystyle 2$ = 𝑖 𝑛$\displaystyle 2$ 𝑛$\displaystyle 1$+ 𝑛$\displaystyle 2$ $\displaystyle 66$−𝑝$\displaystyle 1$ = $\displaystyle 0.5$ × 𝑝$\displaystyle 1$ = $\displaystyle 63.61$𝑡𝑜𝑟𝑟