Example 1 · level 1
Choose the coefficients (in order) that balance: Cu + O₂ → CuO
- 2, 1, 2
- 2, 3, 2
- 3, 1, 2
- 2, 2, 2
Show solution
- Balanced: 2Cu + O₂ → 2CuO.
- Cu: 2 on the left = 2 on the right.
- O: 2 on the left = 2 on the right.
Answer: 2, 1, 2
CLASS 10 SCIENCE · CHEMICAL REACTIONS AND EQUATIONS
Balancing chemical equations
Atoms are neither created nor destroyed, so the number of atoms of each element must be equal on both sides. Change only the coefficients, never the subscripts.
Loading practice…
Worked examples
Example 2 · level 2
Choose the coefficients (in order) that balance: KClO₃ → KCl + O₂
- 3, 2, 3
- 4, 2, 3
- 1, 2, 3
- 2, 2, 3
Show solution
- Balanced: 2KClO₃ → 2KCl + 3O₂.
- K: 2 on the left = 2 on the right.
- Cl: 2 on the left = 2 on the right.
- O: 6 on the left = 6 on the right.
Answer: 2, 2, 3
Example 3 · level 3
Choose the coefficients (in order) that balance: Fe₂O₃ + CO → Fe + CO₂
- 1, 5, 2, 3
- 1, 2, 2, 3
- 1, 3, 2, 3
- 1, 4, 2, 3
Show solution
- Balanced: Fe₂O₃ + 3CO → 2Fe + 3CO₂.
- Fe: 2 on the left = 2 on the right.
- O: 6 on the left = 6 on the right.
- C: 3 on the left = 3 on the right.
Answer: 1, 3, 2, 3