Solutions question bank (Chemistry)

The vapour pressure of benzene at a certain temperature is $640 \mathrm{~mm}$ of $\mathrm{Hg} .$ A non-volatile and non-electrolyte solid weighing $2.175 \mathrm{~g}$ is added to $39.08 \mathrm{~g}$ of benzene. If the vapour pressure of the solution is $600 \mathrm{~mm}$ of $\mathrm{Hg}$, what is the molecular weight of solid substance?

9 gram anhydrous oxalic acid (mol. Wt. = 90) was dissolved in 9.9 moles of water. If vapour pressure of pure water is $P_1^{o}c$ the vapour pressure of solution is