pH comparison of weak vs. strong acids

Steps:

• Identify acid strength: strong acids fully ionize, weak acids partially ionize.
• Compare concentrations: both solutions are 0.1 mol/dm³, so same initial acid amount.
• Calculate H⁺ concentration: strong acid gives [H⁺] = 0.1 mol/dm³; weak acid gives lower [H⁺].
• Determine pH: pH = -log[H⁺], so lower [H⁺] yields higher pH for weak acid.

Why A is correct:

• Ethanoic acid is weak and partially dissociates (Ka ≈ 1.8 × 10⁻⁵), producing fewer H⁺ ions than fully dissociated HCl, resulting in higher pH by the pH formula.

Why the others are wrong:

• B: Some bases, like metal oxides, are insoluble in water and do not produce OH⁻.
• C: Bases react with ammonium salts (e.g., NH₄Cl), not nitrates, to produce ammonia.
• D: Metal oxides are basic, reacting with acids to form salts and water.

Final answer: A