Question

Arrange the following in increasing order (smallest to largest) order of normal boiling point. The normal boiling point of pure water is 100.00 ∘ C and its boiling point elevation constant is 0.512 ∘ C/m
C < B < A < D
D < A < C < B
A < C < B < D
B < C < A < D
A solution is prepared by dissolving 1.22 g of compound in enough water to make up 262 mL in volume. The osmotic pressure of the solution is found to be 30.3 torr at
35.0 °C. Calculate the molar mass of the compound.
257 g/mol
2950 g/mol
3.88 g/mol
44.7 g/mol

Answer 1

The relation between osmotic pressure and molarity of a substance is

π = moles X R X T / volume of solution in litres

π = osmotic pressure

let us convert π  to atm

30.3 torr = 30.3 / 760 atm = 0.0399 atm

T = 35.0 °C = 308.15 K

R = gas constant = 0.0821 L atm / mol K

putting values

0.0399 = moles X 0.0821 X 308.15 / 0.262

Moles = 0.0399 X 0.262 / 0.0821 X 308.15 = 4.132 X 10^-4 moles

Moles  = mass /molar mass

Molar mass = mass/ moles = 1.22 / 4.132 X 10^-4 = 2952.56 g