Salts from neutralisation
Mix an acid and a base together. Both seem to vanish.
- H⁺ ions and OH⁻ ions share the tumbler.
- Each H⁺ pairs with one OH⁻, making water.
- The leftover ions stand together as the salt.
- NaOH + HCl → NaCl + H₂O.
Slide the base volume. Read how much acid it needs.
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The rule
An acid and a base give a salt and water. The same two solutions always neutralise in the same ratio.
Neutralisation is the reaction of an acid with a base. A salt has a metal joined to part of an acid. It is the product besides water. Salt is a family name. Kitchen salt is only one member.
NaOH + HCl → NaCl + H₂O
Common salt comes from a strong acid and a strong base. It is neutral, at pH 7.
Common salt is also a raw material for other chemicals. Passing electricity through its solution is the chlor-alkali process:
2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂
Baking soda comes from common salt too. Water, carbon dioxide and ammonia are added:
NaCl + H₂O + CO₂ + NH₃ → NH₄Cl + NaHCO₃
| Chemical | Kind | One job |
|---|---|---|
| Sodium hydroxide | base | soap and paper making |
| Baking soda, NaHCO₃ | salt, mildly basic | lifts a batter; cancels stomach acid |
| Washing soda, Na₂CO₃·10H₂O | salt, basic | cleans; softens hard water |
| Bleaching powder | salt | bleaches cloth; cleans drinking water |
Heat splits baking soda: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. Dissolve that sodium carbonate in water and let crystals form. The crystals are washing soda.
Chlorine from that process reacts with dry slaked lime, Ca(OH)₂. This makes bleaching powder.