Give examples and explain with equations:
(a)Two colourless solution give a black precipitate on mixing.
(b)Two colourless solutions give a red precipitate on mixing, soluble in excess of one of them.
( c)Two colourless solutions give a white precipitate on mixing, soluble in ammonium hydroxide.
(d)Two colourless solutions give a yellow precipitate on mixing.

Explanation

(a)Lead salt+sodium sulphide.
`Pb(CH_(3)COO)_(2)+Na_(2)Stounerset("Black")(PbS)+2CH_(3)COONa`
(b)`HgCl_(2)+2Kl to underset("Read")(Hgl_(2))+2KCl`
`Hgl_(2)+2Kl to K_(2)Hgl_(4)`
( c)`AgNO_(3)+NaCl to underset("White ppt.")(AgCl)+NaNO_(3)`
`AgCl+2NH_(4)OH to underset("soluble")(Ag(NH_(3))_(2)) Cl+2H_(2)O`
(d)`Pb(NO_(3))_(2)+2Kl to underset("Yellow ppt.")(Pbl_(2)+2KNO_(3))`