Balancing chemical equations
Change the big numbers in front, never the small subscripts.
The common mistake
Changing subscripts (H₂O to H₂O₂) to balance, which changes the substance itself.
Instead: Count atoms of each element on both sides and add coefficients in front of whole formulas until they match.
Worked example with Guide me
Balance H₂ + O₂ → H₂O.
- Sugar · Oxygen atoms on each side?Student · 2 on the left, 1 on the right.
- Sugar · Put 2 in front of H₂O. Now hydrogen?Student · 4 on the right, 2 on the left.
- Sugar · Fix hydrogen.Student · 2H₂ + O₂ → 2H₂O.
Answer: 2H₂ + O₂ → 2H₂O
Try 3 practice questions
1. Balance N₂ + H₂ → NH₃.
Show answer
N₂ + 3H₂ → 2NH₃
2. Balance Mg + O₂ → MgO.
Show answer
2Mg + O₂ → 2MgO
3. Balance CH₄ + O₂ → CO₂ + H₂O.
Show answer
CH₄ + 2O₂ → CO₂ + 2H₂O
Quick answers
- What is the most common mistake with balancing chemical equations?
- Changing subscripts (H₂O to H₂O₂) to balance, which changes the substance itself.
- How do I get balancing chemical equations right?
- Count atoms of each element on both sides and add coefficients in front of whole formulas until they match.
- Can you show a worked example?
- Balance H₂ + O₂ → H₂O. 2H₂ + O₂ → 2H₂O
Related concepts
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