aqueous solution of sodium hydroxides used to test for the presence of
metal ions. Sodium hydroxide, also known as caustic soda, is a strong alkaline solution that reacts with metal cations to form insoluble hydroxides. This reaction results in the precipitation of a colored solid or a colored solution, which can help identify the presence of specific metal ions in a solution.
For example, when sodium hydroxide is added to a solution containing copper ions, a bluish-green precipitate of copper hydroxide forms. This can be used as a qualitative test for the presence of copper ions in the solution. Similarly, the formation of a white precipitate when sodium hydroxide is added to a solution containing calcium ions can indicate the presence of calcium ions.
Overall, the use of sodium hydroxide as a reagent in qualitative analysis helps in identifying the presence of various metal ions in a solution based on the specific reactions they undergo with the alkaline solution.