Chemical reactions with acids and alkali

Observations when acid reacts with metal

effervescence seen

test-tube feels warmer

metal becomes smaller in size

solution may change colour

general word equation for acid + metal

acid + metal → salt + hydrogen gas

Determine presence of hydrogen

Place a lighted splint at the mouth of the test-tube. If hydrogen is present, splint will extinguish with a ‘pop’ sound

unreactive metals

Gold

silver

bronze

observations when acid reacts with a metal carbonate

Effervescence seen

solution may change in colour

Chloride carbonate becomes smaller in size

general word equation for acid + metal carbonate

acid + carbonate → salt + water + carbon dioxide

determine presence of carbon dioxide

bubble the gas into a test-tube of limewater (calcium hydroxide) if carbon dioxide is present white precipitate will form in lime water

Observation when acid reacts with alkali

Bottom of test tube feels warm

Neutralisation

a chemical reaction where and acid reacts with alkali to form salt and water only

general word equation for acid + alkali

acid + alkali → salt + water

Observation when alkali reacts with ammonium salt

colourless and pungent gas produced

general word equations for alkali + ammonium salt

alkali + ammonium salt → salt + water + ammonia gas

determine presence of ammonia gas

place a moist red litmus paper at the mouth of the test tube if ammonia gas is present moist red litmus paper will turn blue