What methods are used to prepare insoluble salts?

Insoluble salts are typically prepared using the precipitation method or double decomposition reaction.

The precipitation method is the most common way to prepare insoluble salts. This involves mixing two soluble salts in a solution, which react to form an insoluble salt that precipitates, or falls out of the solution. For example, if you mix solutions of silver nitrate and sodium chloride, you get a precipitate of silver chloride, which is an insoluble salt. The reaction can be represented as follows: AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq). The (aq) indicates that the substances are dissolved in water, and the (s) indicates that the product is a solid.

The double decomposition reaction is another method used to prepare insoluble salts. This involves two soluble salts reacting to form two new compounds, one of which is an insoluble salt. For example, if you mix solutions of barium chloride and sodium sulphate, you get a precipitate of barium sulphate, which is an insoluble salt. The reaction can be represented as follows: BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq).

In both methods, the insoluble salt can be collected by filtration, washed with distilled water to remove any remaining soluble salts, and then dried. It's important to note that not all reactions will produce a precipitate, as it depends on the solubility of the products formed. Therefore, it's crucial to understand the solubility rules in order to predict whether a precipitate will form in a reaction.

IGCSE Chemistry Tutor Summary: Insoluble salts are made by mixing two solutions that react to create a solid salt that doesn't dissolve, called precipitation, or through a double decomposition reaction, where two new compounds are formed, including the insoluble salt. The solid salt is then separated by filtering, cleaned, and dried. Understanding which reactions make a precipitate is key due to solubility rules.