What happens when ?
(a)Copper sulphate is treated with excess of `NH_(4)OH`
(b)Bismuth chloride is treated with sodium stannite solution in presence of `NaOH`.
( c)Stannous chloride is treated with mercuric chloride.

Explanation

(a)`CuSO_(4)+2NH_(4)OH to Cu(OH)_(2)+(NH_(4))_(2)SO_(4)`
`Cu(OH)_(2)+(NH_(4))_(2)SO_(4)+2NH_(4)OH to Cu(NH_(3))_(4)SO_(4)+4H_(2)O`
(b)`2BiCl_(3)+3Na_(2)SnO_(2)+6NaOHto2Bi+3Na_(2)SnO_(3)+6NaCl+3H_(2)O`
( c)`2HgCl_(2)+SnCl_(2)toHg_(2)Cl_(2)+SnCl_(4)`
`Hg_(2)Cl_(2)+SnCl_(2) to 2Hg+SnCl_(4)`