“The following pairs of compounds can be distinguished by simple test−tube reactions. For each pair of compounds, give a reagent (or combination of reagents) that, when added separately to each compound, could be used to distinguish between them. State what is observed in each case. Aqueous magnesium chloride and aqueous barium chloride”
The Correct Answer and Explanation is :
To distinguish between aqueous magnesium chloride (MgCl₂) and aqueous barium chloride (BaCl₂), you can use sodium sulfate (Na₂SO₄) as the reagent.
Test:
- Add sodium sulfate (Na₂SO₄) solution to both aqueous magnesium chloride and aqueous barium chloride separately.
Observations:
- Magnesium chloride (MgCl₂): When sodium sulfate is added to magnesium chloride, no precipitate forms. This is because magnesium sulfate (MgSO₄) is highly soluble in water and does not form a precipitate under normal conditions.
- Barium chloride (BaCl₂): When sodium sulfate is added to barium chloride, a white precipitate of barium sulfate (BaSO₄) forms. Barium sulfate is insoluble in water, so it will precipitate out of the solution.
Explanation:
The key to distinguishing between magnesium chloride and barium chloride lies in the solubility of their sulfate salts. Both magnesium sulfate (MgSO₄) and barium sulfate (BaSO₄) are formed when sodium sulfate is added to magnesium chloride and barium chloride, respectively. However, the solubility properties of these salts are different:
- Magnesium sulfate (MgSO₄) is soluble in water, so no precipitate forms when sodium sulfate is added to magnesium chloride.
- Barium sulfate (BaSO₄) is insoluble in water, and thus, it forms a white precipitate when sodium sulfate is added to barium chloride.
This difference in solubility is the basis for distinguishing between the two compounds in solution. The formation of a white precipitate in the case of barium chloride provides a clear visual indication that the compound in question is barium chloride, while no precipitate indicates the presence of magnesium chloride.
In summary, sodium sulfate acts as an effective reagent to distinguish between magnesium chloride and barium chloride based on the solubility of their respective sulfate salts.