Properties of Calcium Oxide

Steps:

• Recall calcium oxide (CaO) is a basic oxide formed by heating limestone (CaCO3).
• Evaluate A: Check if CaO reduces with Mg, using reactivity series where Mg is above Ca.
• Evaluate B: Analyze thermal decomposition of Ca(NO3)2, which yields CaO, NO2, and O2.
• Evaluate C: Test CaO's reaction with water, forming Ca(OH)2.
• Note D lacks a statement, preventing evaluation.

Why C is correct:

• Calcium oxide reacts vigorously with cold water to form calcium hydroxide: CaO + H2O → Ca(OH)2, as basic oxides neutralize water.

Why the others are wrong:

• A: Calcium oxide cannot be reduced by magnesium, as both are in group 2; reduction requires a stronger reducing agent like electrolysis.
• B: Heating calcium nitrate produces calcium oxide but also nitrogen dioxide and oxygen: 2Ca(NO3)2 → 2CaO + 4NO2 + O2; statement is incomplete.
• D: Not enough information, as no statement provided.

Final answer: C