The aqueous solution which has pH > 7 is

Step 1: Analyze the question We need the salt whose aqueous solution is basic (pH > 7). This depends on the acid and base that formed the salt, and on whether the salt hydrolyses in water.

Step 2: The concept

• Salt of a strong acid + strong base: neutral (pH = 7)
• Salt of a strong acid + weak base: acidic (pH < 7)
• Salt of a weak acid + strong base: basic (pH > 7)

Step 3: Examine each option

• A. FeCl₃: formed from HCl (strong acid) and Fe(OH)₃ (weak base). The Fe³⁺ ion hydrolyses and releases H⁺, so the solution is acidic. Fe³⁺ + 3H₂O ⇌ Fe(OH)₃ + 3H⁺

• B. CuSO₄: formed from H₂SO₄ (strong acid) and Cu(OH)₂ (weak base). The solution is acidic.

• C. KNO₃: formed from HNO₃ (strong acid) and KOH (strong base). The solution is neutral (pH ≈ 7).

• D. Na₂CO₃: formed from H₂CO₃ (weak acid) and NaOH (strong base). The carbonate ion hydrolyses and releases OH⁻, so the solution is basic. CO₃²⁻ + H₂O ⇌ HCO₃⁻ + OH⁻

Step 4: Answer Na₂CO₃ is the only salt that gives a pH greater than 7, so the answer is D.

Tip: Remember "the stronger parent wins." Look at the acid and base that made the salt. Whichever is strong decides whether the solution is acidic or basic. Transition metal salts such as Fe³⁺ and Cu²⁺ are almost always acidic, and carbonates are basic.