Action of Ammonium Hydroxide on Salts

Ammonium hydroxide is an important compound in Chemistry. Let us first know about it.

Ammonium Hydroxide is the solution of ammonia in water.

It is a colourless, aqueous solution.

$N H_{4} O H$ acts as a weak base as it dissociates in water to yield a low amount of hydroxyl ions.

Let's look at chemical reactions of ammonium hydroxide on important salts.

Ammonium hydroxide reacts with different salts to form different coloured precipitates. Looking at the colour of the ppt, we can identify the salts very easily.

Some precipitates dissolve in excess of ammonium hydroxide, whereas some may not.This also helps to identify the salts. Let us see the examples one by one.

Copper sulphate reacts with ammonium hydroxide to form a pale blue ppt of Copper hydroxide and ammonium sulphate.

The pale blue ppt of $C u (O H)_{2}$ dissolves in excess of $N H_{4} O H$ .

Zinc sulphate reacts with ammonium hydroxide to form a white gelatinous precipitate of $Z n (O H)_{2}$ and ammonium sulphate.

$Z n S O_{4}$ + $2 N H_{4} O H$ ⟶ $(N H_{4})_{2} S O_{4}$ + $Z n (O H)_{2}$ ↓ (white gelatinous ppt)

White gelatinous ppt of $Z n (O H)_{2}$ dissolves in excess of $N H_{4} O H$ to form colourless solution.

Similar to zinc sulphate, zinc chloride also reacts with ammonium hydroxide to form a white gelatinous ppt of $Z n (O H)_{2}$ and ammonium chloride.

$Z n C l_{2}$ + $2 N H_{4} O H$ ⟶ $2 N H_{4} C l$ + $Z n (O H)_{2}$ ↓ (white gelatinous ppt)

White gelatinous ppt of $Z n (O H)_{2}$ dissolves in excess of $N H_{4} O H$ to form colourless solution.

Ferric chloride reacts with ammonium hydroxide to form a ppt of $F e (O H)_{3}$ which is reddish brown in colour and also ammonium chloride.

$F e C l_{3}$ + $3 N H_{4} O H$ ⟶ $3 N H_{4} C l$ + $F e (O H)_{3}$ ↓(reddish brown ppt.)

With excess of NH4OH the reddish brown ppt of FeCl3 is insoluble.

Ferrous sulphate on reacting with ammonium hydroxide produces a dirty green ppt of $F e (O H)_{2}$ . Ammonium sulphate is also formed.

$F e S O_{4}$ + $2 N H_{4} O H$ ⟶ $(N H_{4})_{2} S O_{4}$ + $F e (O H)_{2}$ ↓ (dirty green colour ppt)

With excess of $N H_{4} O H$ the dirty green ppt of $F e (O H)_{2}$ is insoluble.

Lead nitrate reacts with ammonium hydroxide to form a chalky white ppt of $P b (O H)_{2}$ .

Pb(NO3)2 + 2NH4OH ⟶ (NH4)2NO3 + Pb(OH)2 ↓ (chalky white colour ppt)

With excess of NH4OH the chalky white ppt of Pb(OH)2 is insoluble.

Revision.

Ammonium hydroxide reacts with different salts to form different coloured precipitates. Looking at the colour of the ppt, we can identify the salts very easily.

Copper sulphate reacts with ammonium hydroxide to form a pale blue ppt of Copper hydroxide and ammonium sulphate.

Zinc sulphate reacts with ammonium hydroxide to form a white gelatinous precipitate of $Z n (O H)_{2}$ and ammonium sulphate.

Similar to zinc sulphate, zinc chloride also reacts with ammonium hydroxide to form a white gelatinous ppt of $Z n (O H)_{2}$ and ammonium chloride.

Ferric chloride reacts with ammonium hydroxide to form a ppt of $F e (O H)_{3}$ which is reddish brown in colour and also ammonium chloride.

Ferrous sulphate on reacting with ammonium hydroxide produces a dirty green ppt of $F e (O H)_{2}$ . Ammonium sulphate is also formed.

Lead nitrate reacts with ammonium hydroxide to form a chalky white ppt of $P b (O H)_{2}$ .

End