Flexi Says: When sodium hydroxide solution is added to copper sulfate solution blue precipitate of copper hydroxide is formed along with sodium sulfate solution. The reaction is an example of a double displacement in which the positive and negative ions of two ionic compounds exchange places to form two new compounds. Precipitates form in a double-displacement reaction when the cations from one of the reactants combine with the anions from the other reactant to form an insoluble ionic compound. Such types of reactions are known as precipitation reactions.
