Question

In the group analysis of cations, Ba$^{2+}$ & Ca$^{2+}$ are precipitated respectively as 
 

• A. hydroxide & carbonate
• B. sulphide & sulphide
• C. chromate & sulphide
• D. carbonate & carbonate

Hint:

Carbonate precipitation is a key step in identifying alkaline earth metal ions like Ba$^{2+}$ and Ca$^{2+}$ during qualitative inorganic analysis.

Answer 1

The Correct Option is D

Step 1: Understanding group analysis of cations.
In qualitative inorganic analysis, cations are separated into different groups based on selective precipitation using specific group reagents. Barium (Ba$^{2+}$) and Calcium (Ca$^{2+}$) belong to the alkaline earth metals and show similar chemical behavior.
Step 2: Precipitation of Ba$^{2+}$.
Ba$^{2+}$ ions are precipitated as barium carbonate (BaCO$_3$) when ammonium carbonate is added in the presence of ammonium chloride and ammonium hydroxide. Barium carbonate is insoluble and forms a white precipitate.
Step 3: Precipitation of Ca$^{2+}$.
Ca$^{2+}$ ions are also precipitated as calcium carbonate (CaCO$_3$) under the same group analysis conditions. Calcium carbonate is insoluble in water and separates as a white precipitate.
Step 4: Analysis of options.
(A) Hydroxides of Ba$^{2+}$ and Ca$^{2+}$ are soluble, so this option is incorrect.
(B) Sulphides of Ba$^{2+}$ and Ca$^{2+}$ are soluble, hence incorrect.
(C) Chromate precipitation is not used for Ca$^{2+}$ in group analysis, so this option is incorrect.
(D) Both Ba$^{2+}$ and Ca$^{2+}$ form insoluble carbonates, which precipitate during analysis.
Step 5: Conclusion.
Therefore, both Ba$^{2+}$ and Ca$^{2+}$ are precipitated as carbonates in qualitative group analysis.