Reactivity of group 2 metal vs. non-metal with O2 and Cl2 determines solution acidity Steps: - Magnesium (metal) forms basic oxide MgO, which reacts with water to give Mg(OH)2 (pH >7); phosphorus (non-metal) forms acidic oxide P4O10, which reacts with water to give H3PO4 (pH <7), so Mg oxide has higher pH. - Magnesium chloride MgCl2 dissolves in water to give neutral solution (pH ≈7); phosphorus chloride (e.g., PCl5) hydrolyzes with water to give H3PO4 (pH <7), so Mg chloride has higher pH. - Compare pH values: higher for Mg oxide (basic vs. acidic) and higher for Mg chloride (neutral vs. acidic). - Select option matching both higher pH for magnesium. Why A is correct: - Group 2 metals form basic oxides and neutral chlorides; non-metals form acidic oxides and hydrolyzable chlorides producing acids, per periodic trends in reactivity. Why the others are wrong: - B: Phosphorus chloride produces acid, so lower pH than Mg. - C: Phosphorus oxide produces acid, so lower pH than Mg. - D: Both phosphorus compounds produce acids, so lower pH than Mg. Final answer: …