Chemistry · Acids & bases

Neutralisation Lab.

An acid and a base cancel each other out: H⁺ ions from the acid meet OH⁻ ions from the base and become plain water. What's left behind is a salt, and the acid and base you start with decide exactly which salt it is.

Neutralisation in everyday life

Indigestion tablets

Too much hydrochloric acid in your stomach causes heartburn. Antacids contain bases such as magnesium hydroxide or calcium carbonate that neutralise the extra acid.

Garden lime

Soil that is too acidic stunts plants. Farmers and gardeners spread lime (calcium carbonate or calcium hydroxide) to raise the pH of the soil.

Baking

Baking powder is sodium hydrogen carbonate mixed with a dry acid. Add water and they react, making carbon dioxide bubbles that make a cake rise.

Check you've got it

Key words

AcidA substance that releases H⁺ ions in water. pH below 7. Examples: HCl, HNO₃, H₂SO₄

Base · alkaliA base neutralises an acid (metal hydroxides, oxides and carbonates). An alkali is a base that dissolves in water, giving OH⁻ ions. pH above 7

NeutralisationAcid + base → salt + water. The H⁺ and OH⁻ ions join up: H⁺ + OH⁻ → H₂O

SaltThe ionic compound left behind: its metal comes from the base and its name ending from the acid (chloride, nitrate, sulfate)

pH and indicatorspH 7 is neutral; the fewer H⁺ ions, the higher the pH. Universal indicator is red in strong acid, green at 7, purple in strong alkali

Spectator ionsIons that take no part in the reaction, such as Na⁺ and Cl⁻ when sodium hydroxide neutralises hydrochloric acid

Where this connects: the acid formulas and acids with metals are in the Metal Reactions Lab; how ions form is in Inside an Atom; ionic compounds like the salts here are in the Precipitate Lab.

Narration voice: Max, generated with ElevenLabs.