Preparation of a soluble salt
Method overview
Warm dilute acid, add the insoluble solid in small portions until some remains, filter off excess solid, gently evaporate filtrate to concentrate, cool to crystallise, filter and dry crystals.
Apparatus set-up
Diagramdilute acid; insoluble oxide/carbonate; beaker; spatula; filter funnel; evaporating basin; water bath/heater
Independent variable
mass of excess solid added or acid used
Dependent variable
yield/purity of dry salt crystals
Control variables
acid concentration/volume; heating; crystallisation conditions
Apparatus
dilute acid; insoluble oxide/carbonate; beaker; spatula; filter funnel; evaporating basin; water bath/heater
Safety
Wear eye protection; acids are irritants; heat gently; take care with hot apparatus.
Scientific rationale
Excess insoluble solid ensures all acid is neutralised; filtration removes excess reactant; cooling a concentrated solution forms crystals.