The vapour pressure of pure benzene (C_(6)H_(6)) at a given temperature is 640 mm Hg. 2.2g of non - volatile solute is added to 40 g benzene. The vapour pressure of the solution is 600 mm Hg. Calculate the molar mass of the solute ?

The vapour pressure of pure benzene (C_(6)H_(6)) at a given temperatur

1.	The vapour pressure of pure benzene (C_(6)H_(6)) at a given temperature is 640 mm Hg. 2.2g of non - volatile solute is added to 40 g benzene. The vapour pressure of the solution is 600 mm Hg. Calculate the molar mass of the solute ?
Answer» Solution :`P_(C_(6)H_(6))^(0)=640` mm Hg, `W_(2)=2.2` G (no volatile solute), `W_(1)=40` g (benzene) `P_("solution")=600` mm Hg, `M_(2)=?` `(P^(0)-P)/(P^(0))=x_(2)` `(640-600)/(640)=(n_(2))/(n_(1)+n_(2))""[becausen_(1)gt gtn_(2),n_(1)+n_(2)~~n_(1)]` `(40)/(640)=(n_(2))/(n_(1))` `0.0625=(W_(2)xxM_(1))/(M_(2)xxW_(1))` `M_(2)=(2.2xx78)/(0.0625xx40)=68.64" g MOL"^(-1)`