3.1.7—Neutralization reactions
- Syllabus
- First assessment 2025
- Objective
- 3.1.7
- Level
- SL
Acids neutralize metal oxides and hydroxides to form salt and water. Carbonates and hydrogencarbonates also produce carbon dioxide when the reaction requires it; balance all formulae and coefficients.
Identify the parent acid and parent base of a salt by tracing its anion and cation back to the neutralization reactants.
Balance proton capacity as well as atoms: H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O, while an acid–carbonate reaction also releases CO₂. To identify parents of Na₂SO₄, trace SO₄²⁻ to the acid and Na⁺ to the base rather than treating the salt name as a reaction equation.
Representative question
Write two equations showing how these antacids neutralize excess hydrochloric acid.
Magnesium carbonate:
Aluminium hydroxide:
MgCO3(s)+2HCl(aq)→MgCl2(aq)+H2O(l)+CO2(g)Al(OH)3(s)+3HCl(aq)→AlCl3(aq)+3H2O(l)
Accept appropriate ionic equations.
Do not accept H2CO3 as a product of the first reaction.
Ignore equilibrium arrows.
Retrieve the route: track proton transfer and conjugates, calculate pH and Kw, distinguish strength, balance neutralization, read titration curves, use Ka/Kb and hydrolysis, select indicators, and explain and calculate buffer behaviour.
Check donor versus acceptor, one-proton differences, logarithm direction, ion comparison, strength versus concentration, equivalence versus endpoint, pKa landmarks, conjugate equations and dilution ratios.