Answer. When caustic soda NaOH reacts with copper salt it gives blue precipitates of cupric hydroxide.
CuS04(aq) + 2NaOH(aq) Cu(OH)2(8)+ Na2SO4(aq)
Blue ppt.
When caustic soda reacts with zinc salt, it gives white precipitates of zinc hydroxide.
ZnCl2(aq) + 2NaOH(aq) Zn(OH)2 (s) + 2NaCl(aq)
White ppt.
When caustic soda reacts with ferric salt, it gives brown precipitates of ferric hydroxide.
FeCl3 (aq) + 3NaOH(aq) Fe(OH)3 (s) + 3NaCl(aq)
Brown ppt.