#5
Chemical equations (word → symbol, balancing)
Paper 1 · Higher combined
Key steps (method)
- Convert word equations into symbol equations.
- Balance using coefficients (numbers in front), not subscripts.
- Check atoms on both sides match.
- Add state symbols if asked: (s), (l), (g), (aq).
Common mistakes
- Changing subscripts when balancing.
- Forgetting diatomic elements (H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂).
- Missing state symbols or using them incorrectly.
Exam-style questions (quick)
- Balance: CH₄ + O₂ → CO₂ + H₂O.
- Write the symbol equation for magnesium + hydrochloric acid → magnesium chloride + hydrogen.
- Explain what a coefficient means in a balanced equation.