Metal ions that form soluble carbonates in presence of
NH4Cl
ABa
BCa
CMg
DSr
Answer:
C. Mg
Read Explanation:
Group Separation in Qualitative Analysis
- In systematic salt analysis, metal ions are classified into groups based on the solubility of their precipitates.
- Group V cations consist of Barium (Ba²⁺), Strontium (Sr²⁺), and Calcium (Ca²⁺).
- These ions are precipitated as carbonates by adding ammonium carbonate in the presence of Ammonium Chloride (NH₄Cl) and Ammonia (NH₃).
Role of Reagents
- Ammonium Chloride (NH₄Cl): Its primary function is to suppress the dissociation of ammonium carbonate and prevent the premature precipitation of ions from other groups (like Group III and IV).
- pH Regulation: It lowers the concentration of carbonate ions (CO₃²⁻) through the common ion effect, ensuring that the solubility products (Ksp) of Group V carbonates are exceeded while preventing the precipitation of magnesium or other impurities.
Solubility Characteristics
- In the presence of NH₄Cl and NH₃, the cations of Group I, II, III, and IV do not form carbonates, whereas the Group V metals (Ba, Sr, Ca) precipitate as insoluble carbonates.
- Metal ions that form soluble carbonates under these conditions are primarily the Alkali metals (Group 1), such as Sodium (Na⁺) and Potassium (K⁺), as all common alkali metal carbonates are highly soluble in water.
- Magnesium (Mg²⁺) ions remain in the filtrate (solution) in the presence of NH₄Cl, as the formation of magnesium carbonate is inhibited, making them effectively 'soluble' in this specific analytical scheme.