Balancing chemical equations: Class 10 practice
A balanced equation has the same number of atoms of each element on both sides (law of conservation of mass). Read the method, follow the three worked examples, then try the six questions.
What you should know first
- Chemical formulae
The idea behind balancing chemical equations
A balanced equation has the same number of atoms of each element on both sides (law of conservation of mass). Change only the coefficients in front of formulae, never the subscripts.
Step-by-step method
- Count atoms of each element on both sides.
- Balance elements that appear once on each side first.
- Leave H and O (or a free element) until last.
- Recount every element.
Worked example 1 (Basic)
Balance: Fe + H₂O → Fe₃O₄ + H₂
- Fe: 3 on the left, 3 on the right
- H: 8 on the left, 8 on the right
- O: 4 on the left, 4 on the right
- Balanced: 3Fe + 4H₂O → Fe₃O₄ + 4H₂
- Answer: 3Fe + 4H₂O → Fe₃O₄ + 4H₂
Worked example 2 (Standard)
Balance: CH₄ + O₂ → CO₂ + H₂O
- C: 1 on the left, 1 on the right
- H: 4 on the left, 4 on the right
- O: 4 on the left, 4 on the right
- Balanced: CH₄ + 2O₂ → CO₂ + 2H₂O
- Answer: CH₄ + 2O₂ → CO₂ + 2H₂O
Worked example 3 (Challenge)
Balance: C₂H₆ + O₂ → CO₂ + H₂O
- C: 4 on the left, 4 on the right
- H: 12 on the left, 12 on the right
- O: 14 on the left, 14 on the right
- Balanced: 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O
- Answer: 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O
Common mistakes and misconceptions
- Changing subscripts
- Not recounting after each change
Practice questions
- (Basic) Balance: H₂ + O₂ → H₂O
- (Basic) Balance: N₂ + H₂ → NH₃
- (Standard) Balance: Al + O₂ → Al₂O₃
- (Standard) Balance: Na + H₂O → NaOH + H₂
- (Challenge) Balance: Cu + HNO₃ → Cu(NO₃)₂ + NO₂ + H₂O
- (Challenge) Balance: Zn + HCl → ZnCl₂ + H₂
Answer key with full working
- Q1: H: 4 on the left, 4 on the right → O: 2 on the left, 2 on the right → Balanced: 2H₂ + O₂ → 2H₂O → Answer: 2H₂ + O₂ → 2H₂O
- Q2: N: 2 on the left, 2 on the right → H: 6 on the left, 6 on the right → Balanced: N₂ + 3H₂ → 2NH₃ → Answer: N₂ + 3H₂ → 2NH₃
- Q3: Al: 4 on the left, 4 on the right → O: 6 on the left, 6 on the right → Balanced: 4Al + 3O₂ → 2Al₂O₃ → Answer: 4Al + 3O₂ → 2Al₂O₃
- Q4: Na: 2 on the left, 2 on the right → H: 4 on the left, 4 on the right → O: 2 on the left, 2 on the right → Balanced: 2Na + 2H₂O → 2NaOH + H₂ → Answer: 2Na + 2H₂O → 2NaOH + H₂
- Q5: Cu: 1 on the left, 1 on the right → H: 4 on the left, 4 on the right → N: 4 on the left, 4 on the right → O: 12 on the left, 12 on the right → Balanced: Cu + 4HNO₃ → Cu(NO₃)₂ + 2NO₂ + 2H₂O → Answer: Cu + 4HNO₃ → Cu(NO₃)₂ + 2NO₂ + 2H₂O
- Q6: Zn: 1 on the left, 1 on the right → H: 2 on the left, 2 on the right → Cl: 2 on the left, 2 on the right → Balanced: Zn + 2HCl → ZnCl₂ + H₂ → Answer: Zn + 2HCl → ZnCl₂ + H₂
Syllabus note
This skill is listed under "Chemical Reactions and Equations" for Class 10 in the NCERT/CBSE books. ICSE, IGCSE, IB and state boards may teach it in a different chapter or year.
Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.
Related practice and notes
Frequently asked questions
Which chapter is balancing chemical equations in?
"Chemical Reactions and Equations", Class 10 Chemistry (NCERT/CBSE). Other boards may place it differently.
How were the answers checked?
Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.