1. PRACTICAL METHODS FOR MAKING SALTS: Learn THIS!
eg. lead iodide,
barium sulphate
eg. zinc chloride,
copper sulphate
SALTS
are either
SOLUBLE
INSOLUBLE
made by reacting an ACID with either:
suitable Metal
Carbonate
Alkali or Base
Made by reacting two solutions of soluble salts together to produce a precipitate.
To prepare in the lab we react the substances together, remove excess (the excess ensures all the acid has reacted) metal, carbonate or base by filtration and then evaporate the filtrate to about 1/3 it’s original volume before allowing the salt to crystallise by leaving in a warm place (if you evaporate to dryness you make undesirable anhydrous crystals)
NOTE: sodium, potassium and ammonium salts cannot be made by this method – a titration is performed to get an exactly neutral solution which is then evaporated and crystallised as above.
To prepare in the lab two solutions of carefully
selected soluble salts are mixed together.
The insoluble salt forms a solid precipitate
which can be removed by filtration,washed
(to remove unwanted ions) and then dried.