What are the tests for halide ions using silver nitrate?

Halide ions can be tested using silver nitrate, where different halides produce distinct coloured precipitates.

In a typical test for halide ions using silver nitrate, an aqueous solution of the halide is added to a solution of silver nitrate. This results in the formation of a precipitate as the silver ions react with the halide ions to form silver halides. The colour of the precipitate can be used to identify the specific halide ion present.

If the halide is a chloride ion (Cl-), the precipitate formed is white and is silver chloride (AgCl). This precipitate will dissolve in dilute ammonia. If the halide is a bromide ion (Br-), the precipitate is cream and is silver bromide (AgBr). This precipitate will not dissolve in dilute ammonia but will dissolve in concentrated ammonia. If the halide is an iodide ion (I-), the precipitate is yellow and is silver iodide (AgI). This precipitate will not dissolve in either dilute or concentrated ammonia.

It's important to note that the colours of the precipitates can be difficult to distinguish, especially in small quantities or under poor lighting conditions. Therefore, the ammonia test is crucial to confirm the identity of the halide.

In summary, the test for halide ions using silver nitrate involves observing the colour of the precipitate formed and its solubility in ammonia. This simple yet effective test is a fundamental part of IGCSE Chemistry, helping you to identify and understand the properties of different halide ions.