Question

In 3rd B group why H2S gas is passed through NH4Cl and NH4OH

Answer 1

Common Ion Effect

Explanation:

• In alkaline medium or $NH_4OH$, $H_2S$ gas is passed the $OH^{+}$ ions from the dissociation of $H_2S$ gas combine with hydroxyl ions ($OH^{-}$) from the dissociation of $NH_4OH$ to create nearly non ionized water.
• Ammonium chloride is and ammonium hydroxide is added before passing $H_2S$ gas due to common ion effect.
• Common ion effect : it's the reduction within the ionization of a weak acid/ base because of the presence of a standard ion within the solution. which further suppresses the ionization of $NH_4OH$.

Thus, the $H_2S$ gas is passed due to the common ion effect of weak acid or base.