Question

Consider the following statements:

I. Thermal stabilities of carbonates of alkaline earth metals increases down the group.

II. Except LiOH, hydroxides of all other alkali metals are thermally stable.

III. Li$_2$CO$_3$ is thermally stable whereas, other carbonates of the group are thermally unstable.

IV. Solubilities of hydroxides of alkaline earth metals increases down the group.

Pick out the correct of the following:

• A. I, II, III
• B. II, III, IV
• C. I, II, IV
• D. All

Answer 1

Answer: (C)

I, II, IV

Answer 2

1. Statement I: For alkaline earth metal carbonates, thermal stability increases down the group (e.g., MgCO₃ decomposes easier than CaCO₃, SrCO₃, and BaCO₃). → True.

2. Statement II: Among alkali metal hydroxides, LiOH is known to decompose on heating, while the hydroxides of other alkali metals (NaOH, KOH, etc.) are thermally stable. → True.

3. Statement III: Lithium carbonate (Li₂CO₃) is thermally stable, but so are the other alkali metal carbonates; the statement claiming that only Li₂CO₃ is stable and the others are unstable is incorrect. → False.

4. Statement IV: For alkaline earth metal hydroxides, solubility increases down the group (e.g., Mg(OH)₂ is less soluble than Ca(OH)₂ and Ba(OH)₂). → True.

Thus, the correct statements are I, II, and IV.