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PARTS PER MILLION
Study guide and self-test
“Parts per million” means number of parts of solute per 1 million parts
of total solution.
5 ppm chlorine = 5 g. chlorine per 1 million grams solution
5 ounces chlorine per 1 million ounces solution
5 ng. chlorine per 1 million ng. solution
BUT: This does not tell you how to make up a solution, because you don’t
want to have to weigh your solution to know if you have added enough
solvent.
SO: To make a solution in the lab, you will want to convert ppm to
units like grams / L.
Usually, your solvent in the laboratory will be water. Water has a density of
1 gram /mL.
THEREFORE:
5 ppm chlorine = 5 g. chlorine per 1 million mL water (solution)
= 5 g chlorine / 1000L
If we divide the top and bottom by 1 million (106),
5 ppm chlorine = 5 X 10-6 g chlorine = 5 g chlorine
10 –3 L
1 mL solution
FOR ANY SOLUTE: 1 ppm in water = 1 g / mL
Practice problems:
1. Express a 50 ppm NaCl solution in g/L
2. Express a 330 ppm KCl solution in mg/mL
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Answers:
1. Express a 50 ppm NaCl solution in g/L
1 ppm = 1 g NaCl/ 1 mL
50 ppm = 50 g/mL
Using unit cancellation:
50 g/mL(1g/ 106 g)(1000 mL/L) = 0.05 g/L
2. Express a 330 ppm KCl solution in mg/mL
1 ppm = 1 g KCl/ 1 mL
330 ppm = 330 g/mL
Using unit cancellation:
330 g/mL(1 mg/ 103 g) = 0.33 mg/mL