Only metals ABOVE hydrogen in reactivity series react with dilute acids.
Copper, silver, gold — NO reaction.
ACID + METAL OXIDE → SALT + WATER:
Metal oxides are BASES — they neutralise acids.
CuO + 2HCl → CuCl₂ + H₂O
ZnO + H₂SO₄ → ZnSO₄ + H₂O
Fe₂O₃ + 3H₂SO₄ → Fe₂(SO₄)₃ + 3H₂O
Observation: the metal oxide powder DISSOLVES in the acid as the reaction proceeds. The solution often changes colour as the metal salt forms (e.g. blue for copper sulfate).
Reactions with Hydroxides and Carbonates
ACID + METAL HYDROXIDE → SALT + WATER (neutralisation):
NaOH + HCl → NaCl + H₂O
2KOH + H₂SO₄ → K₂SO₄ + 2H₂O
Ca(OH)₂ + 2HCl → CaCl₂ + 2H₂O
This is a NEUTRALISATION reaction — H⁺ from acid combines with OH⁻ from alkali to form water.
ACID + METAL CARBONATE → SALT + WATER + CARBON DIOXIDE:
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
Na₂CO₃ + H₂SO₄ → Na₂SO₄ + H₂O + CO₂
ZnCO₃ + 2HCl → ZnCl₂ + H₂O + CO₂
Test for CO₂: bubble through limewater → turns milky/cloudy.
Observation: fizzing/effervescence as CO₂ gas is produced. The solid carbonate dissolves as the reaction proceeds.
Summary of products:
Acid + metal → salt + hydrogen
Acid + metal oxide → salt + water
Acid + metal hydroxide → salt + water
Acid + metal carbonate → salt + water + carbon dioxide
⚠️ Common Mistake
Acid + metal carbonate produces THREE products: salt + water + carbon DIOXIDE. Students often forget the water or forget the CO₂. Also: the SALT name comes from the METAL and the ACID — sulfuric acid always gives sulfate salts, hydrochloric acid gives chloride salts, nitric acid gives nitrate salts.
📐 Key Equations
Acid + metal → salt + hydrogen
Acid + metal oxide → salt + water
Acid + metal hydroxide → salt + water
Acid + metal carbonate → salt + water + carbon dioxide
Mg + 2HCl → MgCl₂ + H₂
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
📌 Key Note
Acid + metal → salt + H₂ (metals above H only). Acid + metal oxide → salt + H₂O. Acid + metal hydroxide → salt + H₂O (neutralisation). Acid + carbonate → salt + H₂O + CO₂. H₂: squeaky pop. CO₂: turns limewater milky. Salt name = metal + acid anion.
🎯 Matching Activity — Match the Acid Reaction to its Products
Match each type of reaction to the products formed. — drag the symbols on the right to match the component names on the left.
Acid + metal
Drop here
Acid + metal oxide
Drop here
Acid + metal hydroxide
Drop here
Acid + metal carbonate
Drop here
Salt + water + carbon dioxide — CO₂ turns limewater milky
Salt + water — neutralisation reaction
Salt + hydrogen gas — test with lit splint gives squeaky pop
Salt + water only — no gas produced
⭐ Higher Tier Only
Write ionic equations for neutralisation and precipitation. Net ionic equation: H⁺ + OH⁻ → H₂O. Spectator ions are omitted from ionic equations. Understand that ionic equations show only species that change — spectator ions remain unchanged in solution.
🎯 Test Yourself
Question 1 of 2
1. What are the products when zinc carbonate reacts with sulfuric acid?
2. Magnesium reacts with hydrochloric acid. What salt is produced?
⭐ How Well Do You Understand This Topic?
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