Chemistry – Acids, bases and salts - Preparation of salts | e-Consult

To prepare an insoluble salt by precipitation, you need to react a soluble salt with a soluble salt to form an insoluble salt. For example, barium chloride (BaCl₂) reacts with sodium sulfate (Na₂SO₄) to produce barium sulfate (BaSO₄), which is insoluble.

Reactants: You would need a solution of a soluble salt (e.g., BaCl₂) and a solution of another soluble salt (e.g., Na₂SO₄). The concentrations of the solutions will affect the amount of precipitate formed.

Process: The two solutions are mixed together in a beaker. As the ions from the two soluble salts combine, they form an insoluble salt that comes out of solution as a solid – this is the precipitation reaction. The reaction can be represented as:

BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)

Identifying the formation of a precipitate: The formation of a precipitate can be identified by observing the solution. The solution will become cloudy or opaque as the solid forms. You can also use a filter paper to collect the solid precipitate. The precipitate can then be dried and weighed to determine its mass.