Question

what happens when Ammonia solution is added dropwise and in excess to Al2(SO4)3​

Answer 1

On adding little ammonia solution on copper sulphate solution, we get a pale blue precipitate of copper hydroxide.

CuSO4 + NH4OH -------> Cu(OH)2 + (NH4)2SO4

Now when we add excess ammonia solution, the precipitate dissolves, forming a deep azure blue solution.

Cu(OH)2 + NH4OH + (NH4)2SO4 ------> Cu[(NH3)4]SO4 + H2O

The above complex salt is called copper tetrammene sulphate, which is a deep blue solution.

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