The vapour pressure of acetone at 20^(@)C is 185 torr. When 1.2 g of a non - volatile substance was dissolved in 100 g of acetone at 20^(@)C, its vapour pressure was 183 torr. The molar mass (g mol^(-1)) of the substance is :

The vapour pressure of acetone at 20^(@)C is 185 torr. When 1.2 g of a

1.	The vapour pressure of acetone at 20^(@)C is 185 torr. When 1.2 g of a non - volatile substance was dissolved in 100 g of acetone at 20^(@)C, its vapour pressure was 183 torr. The molar mass (g mol^(-1)) of the substance is :
Answer» <P>32 64 128 488 Solution :Vapour pressure of pure ACETONE `P_(A)^(@)=185` torr Vapour pressure of solution, `P_(S)=183` torr Molar MASS of solvent, `M_(A)=58` g//mol as we know`(P_(A)^(@)-P_(S))/(P_(S))=(n_(B))/(n_(A))` `rArr (185-183)/(183)=(W_(B))/(M_(B))xx(M_(A))/(W_(A))` `rArr (2)/(183)=(1.2)/(M_(B))xx(58)/(100)` `rArr M_(B)=(1.2)/(2)xx(58)/(100)xx183=64` g/mol