Naming salts
- The salt depends on the acid: hydrochloric acid makes chlorides, sulfuric acid makes sulfates and nitric acid makes nitrates.
- The first part of the name comes from the metal (or ammonium) in the base, alkali, carbonate or metal.
- Example: copper oxide + sulfuric acid → copper sulfate + water.
Reactions that make salts
- Acid + metal → salt + hydrogen.
- Acid + metal oxide or hydroxide → salt + water.
- Acid + metal carbonate → salt + water + carbon dioxide. For example: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂.
Formulae of salts
- Use the charges on the ions so the formula has no overall charge.
- Sodium chloride: Na⁺ and Cl⁻ → NaCl. Magnesium sulfate: Mg²⁺ and SO₄²⁻ → MgSO₄.
- Sodium sulfate: Na⁺ and SO₄²⁻ → Na₂SO₄. Magnesium nitrate: Mg²⁺ and NO₃⁻ → Mg(NO₃)₂.
Required practical: making a soluble salt
- Warm dilute sulfuric acid in a beaker (with a Bunsen burner or water bath).
- Add insoluble copper oxide a little at a time, stirring, until no more reacts (it is in excess). This makes sure all the acid has reacted.
- Filter to remove the excess copper oxide. The filtrate is copper sulfate solution.
- Heat the solution gently (on a water bath or electric heater) to evaporate some water, then leave it to cool so crystals form. Filter and dry the crystals.
Key terms
- Salt
- A compound formed when the hydrogen in an acid is replaced by a metal (or ammonium).
- Chloride
- A salt made from hydrochloric acid.
- Sulfate
- A salt made from sulfuric acid.
- Nitrate
- A salt made from nitric acid.
- Excess
- More of a reactant than is needed, so some is left over.
- Crystallisation
- Forming solid crystals from a solution by evaporating the solvent and cooling.
- Filtrate
- The solution that passes through the filter paper.