Iodide and bromide

Method 1:

Separately add the mixture of bromine water and hexane to the solutions of iodide and bromide. Then shake well the solutions:

Iodide solution: The hexane layer (upper layer) changes from colourless to purple. This is because bromine reacts with iodide to give iodine, which dissolves in the hexane layer to give a purple solution.
Br2(aq) + 2I-(aq) → 2Br-(aq) + I2(aq)

Bromine solution. The hexane layer (upper layer) changes from colourless to orange. This is because there is no reaction, and the unreacted bromine dissolves in the hexane layer to give an orange solution.



Method 2:

Separately added silver nitrate solutions to iodide and bromide. Then add concentrated ammonia solution.

Iodide solution: A yellow precipitate is formed when silver nitrate solution is added, but there is no observable change when concentrated ammonia solution is added.
Ag+(aq) + I-(aq) → AgI(s)

Bromide solution: A creamy precipitate is formed when silver nitrate solution is added, and the precipitate dissolves in concentrated ammonia solution to give a colourless solutions.
Ag+(aq) + Br-(aq) → AgBr(s)
AgBr(s) + 2NH3(aq) → [Ag(NH3)2]+(aq) + Br-(aq)



Method 3:

Separately added silver nitrate solutions to iodide and bromide. Then put the reaction mixture under sunlight.

Iodide solution: A yellow precipitate is formed when silver nitrate solution is added, but there is no observable change when the precipitate is put under sunlight.
Ag+(aq) + I-(aq) → AgI(s)

Bromide solution: A creamy precipitate is formed when silver nitrate solution is added, and the precipitate slightly turn grey (purple) when put under sunlight.
Ag+(aq) + Br-(aq) → AgBr(s)
2AgBr(s) → Ag(s) + Br2(aq)
=