Common acids:
Hydrochloric acid: H CL; Sulphuric acid: H₂ SO₄; Nitric acid: HNO₃;Ethanoic acid: CH₃ COOH; Methanoic acid; Carbonic acid; citric acid; tannic acid.
Acids usually react with metals giving off hydrogen and the metal's salt.The metal drives out the hydrogen ions from the acid, e.g.

Mg + H₂ SO₄ = Mg SO₄ + H₂

The more hydrogen ions in the acid, the stronger it is in solution. Strong acids and alkalis can burn on contact. Examples of resultant metal salts are sulphates such as magnesium sulphate above, chlorides or nitrates. The hygrogen ions are positive: H ⁺ ions.

Alkaline solutions contain negative hydroxide ions: OH ^- ions which neutralise acids by drawing off the H⁺ ions. The neutralisation gives off water, e.g.

HCl + Na OH = Na Cl + H₂O and the reaction between the ions:
H ⁺ + OH ^- = H₂O

Bases:
All bases neutralise acids. Bases include metal oxides, metal hydroxides, metal carbonates, metal hydrogen carbonates and ammonia solution.

The pH Scale:
Going from 0 to 14: 0 to 7 acidic in decreasing strength; 7 = neutral; 7 to 14 increasing alkalinity.

Common alkalis:
Sodium hydroxide: Na OH Potassium hydroxide: K OH; Calcium hydroxide: Ca (OH)₂; Ammonia: NH₃

Litmus:
Acids turn litmus red; alkalis turn litmus blue, and neutrals leave litmus unchanged. Phenolphthalene is turned pink by alkaline solutions and remains unchanged by acids or neutrals.

Common salts:
Sodium chloride: Na Cl, calcium carbonate: Ca CO₃, potassium chloride: K Cl, barium sulphate: Ba SO₄, cobalt chloride: COCL₂.6H₂O, zinc chloride: ZnCl₂.6H₂O, copper (II) sulphate: CuSO₄.5H₂O, sodium carbonate: Na₂CO₃.10H₂O, ammonium nitrate: NH₄ NO₃, barium carbonate: Ba CO₃, barium chloride: Ba Cl₂, sodium citrate, ammonium carbonate, lead nitrate, lead sulphate, silver chloride and sodium carbonate.