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 A)

the melting point of a 0.110 m iron(III) chloride solution

Express your answer using three significant figures

answer in ∘C

part B ) the osmotic pressure of a 0.091 M potassium sulfate solution at 298 K

answer in atm

part c ) the boiling point of a 1.27 % by mass magnesium chloride solution

answer in ∘C

Answer 1

part A)

delta Tf = i x Kf x m

0 - Tf = 3.4 x 1.86 x 0.110

Tf = - 0.696 oC

melting point = - 0.696 oC

part B )

Osmatic pressure = i x M x S T

                            = 2.6 x 0.091 x 0.0821 x 298

Osmatic pressure   = 5.79 atm

part c ) the boiling point of a 1.27 % by mass magnesium chloride solution

moles of MgCl2 = 1.27 / 95.211 = 0.0133

molality = 0.0133 / 0.09873 = 0.1347 m

Tb = 100 + 2.7 x 0.512 x 0.1347

     = 100.19 oC

boiling point = 100.19 oC