Question

In the analysis of III group basic radicals of salts, the purpose of adding NH₄CI_(s), to NH₄OH is:

• A. To increase the concentration of OH^- ions.
• B. To precipitate the radicals of group IV and V.
• C. To suppress the dissociation of NH₄OH.
• D. To introduce Cl^- ions.

Answer 1

The Correct Option is C

• In the analysis of III group basic radicals of salts (which typically involves the analysis of ammonium and alkali metal ions), NH₄Cl (ammonium chloride) is added to NH₄OH (ammonium hydroxide) to suppress the dissociation of NH₄OH.
• The addition of NH₄Cl helps to maintain the solution's pH at a lower level by increasing the concentration of NH₄⁺ ions, which shifts the dissociation equilibrium of NH₄OH to the left, thus reducing the concentration of OH⁻ ions.

This helps to prevent the precipitation of certain hydroxides of the basic radicals in the III group, ensuring they remain in solution and are selectively analyzed.

Thus, the correct answer is (C) To suppress the dissociation of NH₄OH.

Answer 2

NH₄Cl is added to the solution of NH₄OH to suppress the dissociation of NH₄OH and maintain a constant concentration of OH⁻ ions. This helps in controlling the pH of the solution, preventing unwanted precipitation of hydroxides.