Practice Conservation of Mass in Chemistry

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

Quick Recap

A fundamental law stating that in any chemical reaction, the total mass of all reactants exactly equals the total mass of all products, because atoms are rearranged but never created or destroyed.

Matter can't vanish or appear from nothing. What goes in equals what comes out.

Example 1

easy
If 10 g of hydrogen reacts with 80 g of oxygen to form water, what is the total mass of water produced?

Example 2

medium
In a sealed container, 50.0 g of calcium carbonate decomposes: \text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2. If 28.0 g of CaO is produced, what mass of \text{CO}_2 is released?

Example 3

easy
A student burns 12 g of magnesium in air and obtains 20 g of magnesium oxide. How much oxygen reacted?

Example 4

easy
If 12 g of magnesium reacts with oxygen to form 20 g of magnesium oxide in a closed container, how many grams of oxygen reacted?
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