Question

Which will not be precipitated after addition of \( \left( NH _{4}\right)_{2} CO _{3} \) in presence of \( NH _{4} Cl :- \) (1) \( Mg \) (2) \( Ba \) [AIMS-20 (3) \( Ca \) (4) \( Sr \)

Answer 1

NH₄Cl is strong electrolyte, it decomposes completely while the NH₄OH is weak base it does not ionises completely. Thus due to presence of common ion \(NH_4^+\) in NH₄Cl it supresses the ionisation of weak NH₄OH in order to decrease the OH^- concentration so that higher group cations will not get precipitated.

NH₄Cl → NH₄ + Cl^-

NH₄OH ↔ NH₄ + OH^-

Mg will not be precipitated after addition of (NH₄)₂ CO₃.