A sample of hard water contains 20 g of ca^2+ions per litre . What is the molarity molality and mole fraction of a sample ?(density=1.2g/ml)
Answers
1. Molality
Molar mass of ethylene glycol =
62.07 g/mL
no. of moles =
4 g
62.07 g.mol
−
1
=
0.6444 mol
Molality =
no. of moles
mass of solvent in kg
Molality =
0.6444 mol
0.060 kg
=
10.7 m
2. Molarity
Molarity
=
no. of moles
volume of solution in litres
Density
=
1.05 g/cm
3
Volume
=
Mass
Density
Volume
=
100 g
1.05 g/mL
=
95.24 mL
=
0.0952 L
Molarity
=
0.6444 mol
0.0952 L
=
6.76 M or 6.76 mol/L
3. Mole fraction
no. of moles of water
=
60 g
18.02 g.mol
-1
=
3.329 mol
Total moles
=
(3.329 + 0.6444) mol
=
3.974 mol
mole fraction of ethylene glycol
=
0.6444
3.974
=
0.162
1. Molality
Molar mass of ethylene glycol
= 62.07 g/mL
no. of moles = 4 g
62.07 g.mol−1
= 0.6444 mol
Molality = no. of moles
mass of solvent in kg
Molality = 0.6444 mol
0.060 kg
= 10.7 m
2. Molarity
Molarity
= no. of moles
volume of solution in litres
Density
=1.05 g/cm
3
Volume
= Mass
Density
Volume
=100 g
1.05 g/mL
=95.24 mL
=0.0952 L
Molarity
=0.6444 mol
0.0952 L
=6.76 M or 6.76 mol/L
3. Mole fraction
no. of moles of water
=60 g
18.02 g.mol-1
=3.329 mol
Total moles
=(3.329 + 0.6444) mol
=3.974 mol
mole fraction of ethylene glycol
=0.6444
3.974
= 0.162