Question

Which one of the following statements is NOT correct about the compounds of alkaline earth metals?

• A. Basic nature increases from Mg(OH)₂ to Ba(OH)₂
• B. Thermal stability decreases from BeCO₃ to BaCO₃
• C. Solubility of sulphates in water decreases from BeSO₄ to BaSO₄
• D. Nitrates of these on heating give oxides

Hint:

Thermal stability of carbonates \textbf{increases} down the group due to the larger cation stabilizing the carbonate ion.

Answer 1

The Correct Option is B

Step 1: Analyze Each Statement Statement 1: Basic Nature of Hydroxides - The basicity of hydroxides increases down the group due to decreasing ionization energy and increasing lattice solubility.
- The correct order: \[ \text{Mg(OH)}_2 < \text{Ca(OH)}_2 < \text{Sr(OH)}_2 < \text{Ba(OH)}_2 \] - This statement is correct. Statement 2: Thermal Stability of Carbonates
- Incorrect because the thermal stability of carbonates increases down the group.
- BeCO₃ is the least thermally stable, while BaCO₃ is the most stable.
- Correct order: \[ \text{BeCO}_3 < \text{MgCO}_3 < \text{CaCO}_3 < \text{SrCO}_3 < \text{BaCO}_3 \] - This statement is incorrect, making it the correct answer to the question. Statement 3: Solubility of Sulphates
- Solubility decreases down the group as hydration energy decreases.
- Correct order: \[ \text{BeSO}_4 > \text{MgSO}_4 > \text{CaSO}_4 > \text{SrSO}_4 > \text{BaSO}_4 \] - This statement is correct. Statement 4: Nitrate Decomposition - All alkaline earth metal nitrates decompose on heating to form metal oxides, NO₂, and O₂.
- Example reaction: \[ \text{Ca(NO}_3)_2 \rightarrow \text{CaO} + 2\text{NO}_2 + \frac{1}{2} O_2 \] - This statement is correct. Final Answer: Statement 2 is incorrect. \bigskip