Distinguish by adding: Sodium hydroxide solution or ammonium hydroxide solution to

(a) Calcium salt solution and lead salt solution

(b) Lead nitrate solution and zinc nitrate solution

(c) Copper salt solution and ferrous salt solution

(d) Fe(II) salt solution and Fe(III) salt solution

(e) Ferrous nitrate and lead nitrate

(a) Sodium hydroxide on reaction with ferrous salt solution gives a dirty green precipitate of Fe(OH)₂ which is insoluble in excess NaOH.

$\underset{\text{colourless/light green}}{{\text{FeSO}$4}} + 2\text{NaOH} \longrightarrow \underset{\text{dirty green ppt}}{\text{Fe(OH)}2 \downarrow} + \text{Na}2\text{SO}4

Sodium hydroxide on reaction with lead salt solution gives a white precipitate of Pb(OH)₂.

$\underset{\text{colourless}}{{\text{Pb(NO}$3)2}} + 2\text{NaOH} \longrightarrow \underset{\text{chalky white ppt}}{\text{Pb(OH)}2 \downarrow} + 2\text{NaNO}3

(b) When ammonium hydroxide solution is added to each of the compounds, lead nitrate forms a chalky white precipitate of lead hydroxide [Pb(OH)₂] which is insoluble in excess of ammonium hydroxide.

$\underset{\text{colourless}}{{\text{Pb(NO}$3)2}} + 2\text{NH}4\text{OH} \longrightarrow \underset{\text{white ppt}}{\text{Pb(OH)}2} ↓ + 2\text{NH}4\text{NO}3

Whereas a gelatinous white precipitate of zinc hydroxide [Zn(OH)₂] is formed in case of zinc nitrate, which is soluble in excess of ammonium hydroxide.

Zn(NO₃)₂ + 2NH₄OH ⟶ 2NH₄NO₃ + Zn(OH)₂ ↓

(c) On adding Sodium hydroxide to Copper salt pale blue coloured precipitate is obtained which is insoluble in excess of Sodium hydroxide. Ferrous salt solution gives a dirty green coloured precipitate with Sodium hydroxide which is insoluble in excess of NaOH.

$\underset{\text{blue}}{{\text{CuSO}$4}} + \underset{\text{colourless}}{2\text{NaOH}} \longrightarrow \underset{\text{pale blue ppt}}{\text{Cu(OH)}2↓} + \underset{\text{colourless}}{\text{ Na}2\text{SO}4}

$\underset{\text{pale green}}{{\text{FeSO}$4}} + \underset{\text{colourless}}{2\text{NaOH}} \longrightarrow \underset{\text{dirty green ppt}}{\text{Fe(OH)}2↓} + \underset{\text{colourless}}{\text{Na}2\text{SO}4}

(d) Sodium hydroxide on reaction with Fe(II) salt gives dirty green coloured precipitate, while with Fe(III) salt solution it forms reddish brown precipitate. Both precipitates are insoluble in excess NaOH.

Fe(II) salt:

$\underset{\text{pale green solution}}{{\text{FeSO}$4}} + 2\text{NaOH} \longrightarrow \underset{\text{dirty green ppt}}{\text{Fe(OH)}2↓} + \underset{\text{colourless in solution}}{\text{Na}2\text{SO}4}

Fe(III) salt :

$\underset{\text{yellow}}{{\text{FeCl}$3}} + \underset{\text{colourless}}{3\text{NaOH}} \longrightarrow \underset{\text{reddish brown ppt}}{\text{Fe(OH)}3↓} + \underset{\text{colourless}}{3\text{NaCl}}

(e) Ammonium hydroxide on reaction with lead nitrate gives a chalky white insoluble precipitate, and with ferrous nitrate forms a dirty green ppt.

$\underset{\text{colourless}}{{\text{Pb(NO}$3)2}} + 2\text{NH}4\text{OH} \longrightarrow \underset{\text{white ppt}}{\text{Pb(OH)}2↓} + 2\text{NH}4\text{NO}3

$\underset{\text{colourless}}{{\text{Fe(NO}$3)2}} + 2\text{NH}4\text{OH} \longrightarrow \underset{\text{dirty green ppt}}{\text{Fe(OH)}2↓} + \underset{\text{ colourless}}{2\text{NH}4\text{NO}3}