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 {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: \[ {Mg(OH)}_2<{Ca(OH)}_2<{Sr(OH)}_2<{Ba(OH)}_2 \] - 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: \[ {BeCO}_3<{MgCO}_3<{CaCO}_3<{SrCO}_3<{BaCO}_3 \] - 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: \[ {BeSO}_4>{MgSO}_4>{CaSO}_4>{SrSO}_4>{BaSO}_4 \] - 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: \[ {Ca(NO}_3)_2 \rightarrow {CaO} + 2{NO}_2 + \frac{1}{2} O_2 \] - This statement is correct. Final Answer: Statement 2 is incorrect.