Question

Use the van't Hoff factors in the table below to calculate each colligative property. Table. Van't Hoff Factors at 0.05 m Concentration in Aqueous Solution Solute i Expected i Measured Nonelectrolyte 1 1 NaCl 2 1.9 MgSO4 2 1.3 MgCl2 3 2.7 K2SO4 3 2.6 FeCl3 4 3.4 part b the osmotic pressure of a 0.084 M potassium sulfate solution at 298 K Part c the boiling point of a 1.12 % by mass magnesium chloride solution

Answer 1

Part B:
Concentration of K2SO4 solution = 0.084 M

Temperature = 298 K

For K2SO4, i = 2.6

Osmotic pressure, = i * c * R * T

= 2.6 * 0.084 * 0.0821 * 298

= 5.34 atm

Part C:
Mass % of magnesium chloride = 1.12%

Mass of magnesium chloride in 100 g solution = 1.12 g

Molar mass of MgCl2 = 95.21 g/mol

Moles of MgCl2 = 1.12 / 95.21 = 0.0117

Mass of solvent = 100 - 1.12

= 98.88 g = 0.09888 kg

Molality of solution = 0.0117 / 0.09888

= 0.118 m

For MgCl2, i = 2.7

Elevation in boiling point, Tb = i * Kb * m

= 2.7 * 0.512 * 0.118

= 0.163 oC

Boiling point of MgCl2 solution = 100 + 0.163

= 100.163 oC