Properties of Calcium Hydroxide

Steps:

• Recall solubility trend in Group 2: solubility of hydroxides increases down the group, so Ca(OH)₂ is less soluble than Sr(OH)₂.
• Identify chemical reaction: Ca(OH)₂ dissociates in water to Ca²⁺ and OH⁻ ions, raising pH above 7.
• Check agricultural use: Ca(OH)₂, or lime, raises soil pH, not lowers it.
• Note incomplete option D provides no evaluable statement.

Why B is correct:

• Calcium hydroxide is a base that reacts with water to produce hydroxide ions (Ca(OH)₂ → Ca²⁺ + 2OH⁻), forming an alkaline solution with pH > 7.

Why the others are wrong:

• A: Incorrect, as Group 2 hydroxide solubility increases down the group, making Ca(OH)₂ more soluble than Mg(OH)₂ but less than Sr(OH)₂.
• C: Incorrect, as it neutralizes acidic soils by increasing pH, not decreasing it.
• D: Not enough information, as the statement is missing.

Final answer: B