Question

4) The Safe Drinking Water Act (SDWA) sets a limit for mercury-a toxin to the central nervous system-at 0.002 ppm by mass. Water suppliers must periodically test their water to ensure that mercury levels do not exceed this limit. Suppose water becomes contaminated with mercury at twice the legal limit (0.004 ppm). How much of this water would have to be consumed for someone to ingest 50 mg of mercury? 5)A solution contains a mixture of pentane and hexane at room temperature. The solution has a vapor pressure of 252 torr . Pure pentane and hexane have vapor pressures of 425 torr and 151 torr, respectively, at room temperature. What is the mole fraction of hexane? (Assume ideal behavior.)

1) The melting point of a 0.150 m iron(III) chloride solution

2)the osmotic pressure of a 0.085 M

potassium sulfate solution at 298 K

3) the boiling point of a 1.15 % by mass magnesium chloride solution

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

Answer 1

5)

solution vapour pressure = P = 252 torr

pure hexane vapoure pressure = Po = 151 torr

P = mole fraction x total pressure

151 = mole fraction x 252

mole fraction of hexane = 0.6

1) The melting point of a 0.150 m iron(III) chloride solution

FeCl3 , i value = 3.4

Tb = i x Kb x m

Tb - To = i x Kb x m

Tb - 100 = 3.4 x 0.52 x 0.150

Tb = 100.265 oC

boiling point = 100.265 oC

2)the osmotic pressure of a 0.085 M potassium sulfate solution at 298 K

i = 2.6

P = i x M x S x T

P = 2.6 x 0.085 x 0.0821 x 298

P = 5.41 atm

osmotic pressure = 5.41 atm

3) the boiling point of a 1.15 % by mass magnesium chloride solution

mass of solute MgCl2 = 1.15 g

mole = 1.15 / 95 = 0.012

mass of solvent = 100 -1.15 = 98.85 g

molality = (moles) x 1000 / solvent mass

= 0.012 x 1000 / 98.85

= 0.122 m

i = 2.7

Tb = i x Kb x m

Tb - To = i x Kb x m

Tb - 100 = 2.7 x 0.52 x 0.122

Tb = 100.17 oC

boiling point = 100.17 oC

note : i do not know 4th problem solution