Worksheet: Purity

In this worksheet, we will practice calculating the purity of a substance based on its proportion by mass.


What is the equation that gives percentage purity in terms of the mass of the pure chemical and the mass of the sample?

  • APercentagepuritymassofsamplemassofpurechemicalmassofsample=×100%.
  • BPercentagepuritymassofsamplemassofpurechemical=×100%.
  • CPercentagepuritymassofpurechemicalmassofsample=×100%.
  • DPercentagepuritymassofsamplemassofpurechemical=.
  • EPercentagepuritymassofpurechemicalmassofsample=.


A mixture of nitrogen and oxygen gas has a mass of 1.20 kg. After 250 g of oxygen in the mixture is reacted with a metal, pure nitrogen is left behind. To 2 significant figures, what is the percentage purity of nitrogen in the original mixture?


An impure sample of aluminum bromide contains 4% contaminants by weight. What is the percentage purity of the sample?


An impure sample of magnesium chloride has a mass of 50 g. After perfect purification, 45 g of magnesium chloride is recovered. What is the percentage purity of the original sample?

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