Conservation of Mass Examples in Chemistry
Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Conservation of Mass.
This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.
Concept 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.
Read the full concept explanation →How to Use These Examples
- Read the first worked example with the solution open so the structure is clear.
- Try the practice problems before revealing each solution.
- Use the related concepts and background knowledge badges if you feel stuck.
What to Focus On
Core idea: Atoms are rearranged into new substances — none are created or destroyed in the process.
Common stuck point: Mass seems to disappear when gases escape—but it's still conserved.
Sense of Study hint: When solving mass conservation problems, set total mass of reactants equal to total mass of products. First add up the masses of all reactants. Then add up the masses of all known products. Finally, solve for the unknown mass using the equation m_{\text{reactants}} = m_{\text{products}}.
Worked Examples
Example 1
easySolution
- 1 State the law of conservation of mass: in a chemical reaction, mass is neither created nor destroyed.
- 2 Add up the masses of all reactants: 10\,\text{g} + 80\,\text{g} = 90\,\text{g}.
- 3 By conservation of mass, the total mass of products must also equal 90\,\text{g}.
Answer
Example 2
mediumPractice Problems
Try these problems on your own first, then open the solution to compare your method.
Example 1
easyExample 2
easyRelated Concepts
Background Knowledge
These ideas may be useful before you work through the harder examples.