Question

Distinguish by adding:
(a) sodium hydroxide solution and
(b) Ammonium hydroxide solution to
(i) Calcium salt solution and lead salt solution
(ii) Lead salt solution and ferrous salt solution
(iii) copper salt solution and ferrous salt solution
(iv) Fe (II) salt solution and Fe (III) Salt solution
(v) Ferrous nitrate and lead nitrate

Answer 1

		adding sodium hydroxide solution to	adding ammonium hydroxide solution to
1	Calcium salt solution	`Ca(NO_3)_2 + 2NaOHCa(OH)_2 + 2NaNO_3`On adding excess of NaOH, ppt. of Ca `(OH)_2` is sparingly soluble	On addition of NH4OH to calcium salts no precipitation of Ca `(OH)_2`occurs even with addition of excess of `NH_4OH` because the concentration of OH-ions from ionization of NH4OH is so low that it cannot precipitate the hydroxide of calcium.
2	lead salt solution	`Pb(NO_3)_2 + 2NaOHPb(OH)_2 + 2NaNO_3`On adding excess of NaOH, ppt of Pb`(OH)_2` is soluble.	`Pb(NO_3)_2 + 2 NH4OHPb(OH)_2 + 2NH_4NO_3`On adding excess of `NH_4OH`, chalky white ppt. of Pb `(OH)_2` is insoluble.
3	Lead salt solution	`Pb(NO_3)_2 + 2NaOHPb(OH)_2 + 2NaNO_3`On adding excess of NaOH, ppt of Pb`(OH)_2`is soluble.	`Pb(NO_3)_2 + 2 NH_4OHPb(OH)_2 + 2NH4_NO_3`On adding excess of NH4OH, chalky white ppt. of `Pb(OH)_2` is insoluble.
4	ferrous salt solution	`ZnSO_4 + 2NaOHZn(OH)_2 + Na_2SO_4`With excess of NaOH, white gelatinous ppt. of Zn`(OH)_2` is soluble. So, these two cannot be distinguished by NaOH alone. However white ppt. of Pb `(OH)_2`is readily soluble in acetic acid also	`ZnSO_4 + 2NH_4OHZn(OH)_2 + (NH_4)_2SO_4`With excess of NH4OH, white gelatinous ppt. of Zn `(OH)_2` is soluble.
5	copper salt solution	`CuSO_4 + 2NaOH        Cu(OH)_2 + Na_2SO_4`With excess of NaOH, alkali pale blue ppt of Cu `(OH)_2` is insoluble.	`CuSO_4 + 2NH_4OHCu(OH)_2 + (NH_4)_2SO_4`With excess of NH4OH, pale blue ppt. of Cu `(OH)_2` is soluble.
6	ferrous salt solution	`FeSO_4 + 2NaOHFe(OH)_2 + Na_2SO_4`With excess of NaOH, dirty green ppt. of Fe`(OH)_2` is insoluble.	`FeSO_4 + 2NH_4OHFe(OH)_2 + (NH_4)_2SO_4`With excess of NH4OH, dirty green ppt. of Fe `(OH)_2` is insoluble.
7	Fe (II) salt solution	`CuSO_4 + 2NaOHCu(OH)_2 + Na_2SO_4`With excess of NaOH, alkali pale blue ppt of Cu `(OH)_2` is insoluble.	`FeSO_4 + 2NH_4OHFe(OH)_2 + (NH_4)_2SO_4`With excess of NH4OH, dirty green ppt. of Fe `(OH)_2` is insoluble.
8	Fe (III) Salt solution	`FeCl_3 + 3NaOHFe(OH)_3 + 3NaCl`With excess of NaOH, reddish brown ppt of Fe `(OH)_3` is insoluble.	`FeCl_3 + 3NH_4OHFe(OH)_3 + 3NH_4Cl` With excess of NH4OH, reddish brown ppt of Fe `(OH)3` is insoluble.