Practice Percent Composition in Chemistry

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

The percentage by mass that each element contributes to the total molar mass of a compound, calculated by dividing the total mass of each element in one mole of the compound by the compound's molar mass and multiplying by 100.

What fraction of the compound's total weight is made up by each element inside it.

Example 1

easy
Calculate the percent composition by mass of each element in \text{H}_2\text{O}.

Example 2

medium
Calculate the percent by mass of nitrogen in ammonium nitrate (\text{NH}_4\text{NO}_3).

Example 3

easy
What is the percent composition of carbon in \text{CO}_2? (C = 12.01, O = 16.00)

Example 4

easy
What percent by mass of calcium carbonate (\text{CaCO}_3) is oxygen? (Ca = 40.08, C = 12.01, O = 16.00)
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