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Match List-I with List-II.
Column I
- A. $\text{Co}^{2+}$
- B. $\text{Mg}^{2+}$
- C. $\text{Pb}^{2+}$
- D. $\text{Al}^{3+}$
Column II
- I. Group-I
- II. Group-III
- III. Group-IV
- IV. Group-VI
Correct answer: A → III, B → IV, C → I, D → II
Explanation
In qualitative salt analysis: $\text{Pb}^{2+}$ is in Group-I, $\text{Al}^{3+}$ is in Group-III, $\text{Co}^{2+}$ is in Group-IV, and $\text{Mg}^{2+}$ is in Group-VI.
Detailed Solution
According to the systematic qualitative cation analysis scheme: Group-I includes $\text{Pb}^{2+}$ (precipitated as chloride with dil. $\text{HCl}$); Group-III includes $\text{Al}^{3+}, \text{Fe}^{3+}$ (precipitated as hydroxides with $\text{NH}_4\text{OH}$ in presence of $\text{NH}_4\text{Cl}$); Group-IV includes $\text{Co}^{2+}, \text{Ni}^{2+}, \text{Mn}^{2+}, \text{Zn}^{2+}$ (precipitated as sulphides with $\text{H}_2\text{S}$ in basic medium); Group-VI includes $\text{Mg}^{2+}$. Thus, A-III, B-IV, C-I, D-II.