Concentration of Solutions

1
Concentration of Solutions

• - A measure of the amount of solute in a
  given amount of solvent or solution.

2
Percent by Mass
Mass of solute
x 100
Total Mass
Solute
x 100
Solute
Solvent

3
Practice

• 1. A solution of sodium chloride is prepared by
  dissolving 5.00g of salt in 550g of water. What
  is the concentration of this solution given as
  percent by mass?

Solute
Givens 5.00g salt 550g water
x 100
Solute
Solvent

Solute
Solvent
5.00g
x 100
5.00g

550g
5.00g
x 100
0.90
555g
4
More Practice

• 2. What mass of salt should be dissolved in
  202 grams of water to make a 43.2 solution?

Solute
x 100
Givens ? g salt 202g water 43.2
Solute
Solvent

Solute
x
x 100
43.2
x

202g
Solvent
100
100
x
0.432
(x 202g)
(x 202g)
x

202g
0.432x
x

87.3g
-0.432x
-0.432x
0.568x

87.3g
x 154 g
0.568
0.568
5
Molarity

• - The number of moles of solute in one liter of
  solution.

moles
mol
Liter
L

• What is the molarity of 3.50L of solution that
  contains 90.0g of NaCl?

Givens ? mol/L 90.0g NaCl 3.50L
90.0g NaCl
1 mol NaCl
0.440 M
58.5g NaCl
3.50 L
6
Practice

• 2. How many grams of HCl are required to make
  0.800L of 0.500M HCl solution?

Givens ? g HCl 0.800L 0.500 M HCl
0.500 mol HCl
1 L
0.500 mol HCl
36.5g HCl
0.800 L
14.6 g HCl
1 L
1 mol HCl
7
More Practice

• 3. What volume of 2.50M NaCl solution can be
  made using 117 grams of sodium chloride?

Givens ? L 2.50M NaCl 117g NaCl
2.50 mol HCl
1 L
1 L
1 mol HCl
117g HCl
1.28L
2.50 mol HCl
36.5g HCl
8
Molality

• - The number of moles of solute in one liter of
  solvent.

moles
mol
kg
kg

• 1. A solution contains 17.1g of sucrose
  (C12H22O11) dissolved in 125g of water. Find the
  molal concentration of the solution.

Givens ? mol/kg 17.1g C12H22O11 125g
17.1g C12H22O11
1 mol C12H22O11
0.125 kg
342.0g C12H22O11
0.125kg
0.400 m
9
Practice

• 2. What mass of iodine must be dissolved in
  100.0g of CCl4 to prepare a 0.480 m solution?

Givens ? g I2 100.0gCCl4 0.480 m I2
0.1000kg
0.480 mol I2
1 kg CCl4
0.480 mol I2
253.8g I2
0.1000 kg CCl4
12.2 g I2
1 kg CCl4
1 mol I2