Solution
Concentrations
Percent by Mass (m/m)
Mass of solute
×100
Mass of solution
Solution = solute + solvent
Example 1
An aquarium must contain 13.6 g NaCl per 100.0 g of water. What is
the percent by mass (m/m) of NaCl in the solution?
Solute:13.6g (smaller #)
+ Solvent: 100.0g (larger #)
Solution: 113.6g
Mass of solute
×100
Mass of solution
13.6
×100 = 11.97% ≈ 12.0%
113.6
Example 2
You have a 650.0g KCL solution. If the percent by mass is 1.25%
(m/m), how many grams of solute is in the solution? How many grams
of solvent are in the solution?
Then remember: solute + solvent = solution
and solve for solvent
Solution: 650.0g
−
Solute: 8.13g
Solvent = 641.87g ≈ 642g
First find solute:
solute
×100 = 1.25%
650.0
Solute = 8.13g
Percent by Volume (v/v)
Volume of solute
×100
Volume of solution
Solution = solute + solvent
Example 3
What is the percent by volume of ethanol in a solution that contains
45mL of ethanol dissolved in 145mL of water?
Then remember: solute + solvent = solution
and solve for solvent
Solute: 45mL (smaller #)
+ Solvent: 145mL (larger #)
Solution: 190mL
45
190
×100 = 23.68% ≈ 24%
Example 4
If you have 200.0 mL of a 35.0% aqueous solution of ethanol, what
volume of ethanol and water are in the solution?
First find solute:
Solution: 200.0mL
−
Solute: 70.0mL
Solvent = 130.0mL
≈ 130. or 1.3×102 mL
solute
×100 = 35.0%
200.0
Solute = 70.0mL
Parts Per Million (ppm)
Solute
×106
Solution
1 ppm = 1mg/L
Example 5
If 25 grams of a chemical is dissolved in 75 grams of water, what is the
concentration of the chemical in parts per million (ppm)?
Solute: 25g (smaller #)
+
Solvent: 75g (larger #)
Solution: 100g
25
100
×106 = 250,000 or 2.5×105 g
Example 6
Suppose 17 grams of sucrose is dissolved in 183 grams of water. What
is the concentration of sucrose in ppm?
Solute: 17g (smaller #)
+
Solvent: 183g (larger #)
Solution: 200g
17
200
×106 = 85,000 or 8.5×104 g
Example 7
150 mL of an aqueous sodium chloride solution contains 0.0045g NaCl.
Calculate the concentration of NaCl in parts per million (ppm).
Remember 1ppm = 1 mg/L So change the mL into L
and the g into mg
0.0045g
150mL
1000mg
1g
1000mL
1L
= 30 mg/L = 30 ppm
Example 8
Convert 0.0035% NaCl by mass into parts per million of NaCl.
* Think of 0.0035% like your
grade on a test; 0.0035% means
0.0035 out of 100
0.0035
×106 = 35ppm
100