Topic 3.1.1: Chemical Equations
Balancing Equations & State Symbols (Paper 4 Focus)
⚠️ Examiner's Protocol
- • Balancing: Coefficients ONLY (never change subscripts)
- • State Symbols: (s)=solid, (l)=liquid, (g)=gas, (aq)=aqueous
- • Common Trap: H₂O in neutralization is (l), not (aq)
- • Formula First: Write correct formulae before balancing
Balancing Equations (5 marks)
Balance the following equation:
Balance the following equation:
Balance the following equation:
Balance the following equation:
Balance the following equation:
State Symbols (5 marks)
Write the state symbol for the product when molten sodium chloride is formed.
Write the state symbol for nitric acid used in a titration.
Write the state symbol for carbon dioxide produced when calcium carbonate is heated.
Write the state symbol for solid copper formed during the displacement reaction: CuSO₄(aq) + Zn(s) → ZnSO₄(aq) + Cu
Complete this equation with state symbols: HCl + NaOH → NaCl + H₂O. All reactants and products are in aqueous solution.
Word to Symbol Equations (10 marks)
Write the balanced symbol equation for: Calcium carbonate → Calcium oxide + Carbon dioxide
Write the balanced symbol equation for: Magnesium + Hydrochloric acid → Magnesium chloride + Hydrogen
Write the balanced symbol equation for: Sodium hydroxide + Sulfuric acid → Sodium sulfate + Water
Write the balanced symbol equation for: Methane + Oxygen → Carbon dioxide + Water (complete combustion)
Write the balanced symbol equation for: Zinc + Copper sulfate → Zinc sulfate + Copper
Mark Scheme Keywords (Paper 4 Essentials)
Balancing Rules:
- • Use coefficients (whole numbers in front)
- • Never change subscripts (numbers in formulae)
- • Start with most complex molecule
- • Balance metals first, then non-metals, then hydrogen and oxygen last
State Symbol Rules:
- • Metal elements are always (s)
- • Acids in reactions are always (aq)
- • Gases produced are (g)
- • Water in neutralization is (l) not (aq)
📊 Total: 20 marks
Section A: 5 marks | Section B: 5 marks | Section C: 10 marks
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