An aqueous solution of Na2CO3 is

Step 1: Analyze the question We need to decide whether a solution of sodium carbonate (Na₂CO₃) in water is acidic, alkaline (basic), amphoteric or neutral.

Step 2: The concept: salt hydrolysis The pH of a salt solution depends on the acid and base that formed it:

• Strong acid + strong base gives a neutral salt.
• Strong acid + weak base gives an acidic salt.
• Weak acid + strong base gives a basic (alkaline) salt.

Step 3: Apply it to Na₂CO₃ Na₂CO₃ is formed from:

• NaOH, a strong base
• H₂CO₃ (carbonic acid), a weak acid

When it dissolves, it dissociates completely:

Na₂CO₃ → 2Na⁺ + CO₃²⁻

• Na⁺ does not react with water, since it comes from a strong base.
• CO₃²⁻ is the conjugate base of a weak acid, so it picks up H⁺ from water (hydrolysis):

CO₃²⁻ + H₂O ⇌ HCO₃⁻ + OH⁻

The extra OH⁻ ions make the solution alkaline, with a pH above 7 (about 11 for typical solutions).

Step 4: Answer The solution is alkaline, which is option B.

Why not the others?

• Acidic: this would need excess H⁺, but hydrolysis produces OH⁻.
• Amphoteric: this describes substances such as Al₂O₃ or ZnO that react with both acids and bases.
• Neutral: this applies to salts like NaCl, from a strong acid and a strong base.

Exam tip: Remember "the strong one wins." Na₂CO₃ has a strong base (NaOH) and a weak acid (H₂CO₃), so the base wins and the solution is alkaline. The same logic applies to NaHCO₃ (mildly alkaline) and CH₃COONa (alkaline). By contrast, NH₄Cl, from a weak base and a strong acid, is acidic.