The vapour pressure of acetone at 20^oC is 185 torr. When 1.2 g of a non-volatile substance was dissolved in
100 g of acetone at 20^oC, its vapour pressure was 183 torr. The molar mass (g mol⁻¹) of the substance is:
JEE Main 2015 · Session, Shift 1 · Q2006