What is a salt? Explain, with one example each, why the solutions of some salts are neutral, some acidic and some basic.

1. 1 · Define. A salt is an ionic compound with a cation other than H⁺ and an anion other than OH⁻. It forms with water in neutralisation.
2. 2 · Neutral. Strong acid + strong base: NaCl (from HCl and NaOH), pH 7.
3. 3 · Basic. Weak acid + strong base: Na₂CO₃ (from H₂CO₃ and NaOH), pH above 7.
4. 4 · Acidic. Strong acid + weak base: NH₄Cl (from HCl and NH₄OH), pH below 7.
5. 5 · Real life. Washing soda solution is basic, which helps it remove grease from vessels.
6. 6 · Close in one line. So the stronger parent decides the nature of a salt's solution.

Scoring tip: Name both parents for each salt. The mark is for linking the strength of the acid and the base to the pH.