Bases yield the highest pH in aqueous solutions

Steps:

• pH = -log[H⁺]; highest pH corresponds to lowest [H⁺] or highest [OH⁻].
• Classify solutions: acids increase [H⁺] (low pH), bases increase [OH⁻] (high pH), salts may be neutral.
• For 1M concentrations, strong acids/bases fully dissociate; HCl and H₂SO₄ are strong acids, NaOH is strong base, NaCl is neutral.
• Compare: NaOH produces 1M OH⁻ (pH ≈ 14), exceeding neutral pH 7 and acidic pH < 7.

Why C is correct:

• NaOH, a strong base, fully dissociates: NaOH → Na⁺ + OH⁻, yielding [OH⁻] = 1M, so pH = 14 (from pH + pOH = 14).

Why the others are wrong:

• A: HCl is a strong acid, fully dissociates to [H⁺] = 1M, pH = 0.
• B: NaCl is a neutral salt from strong acid/base, no H⁺/OH⁻ change, pH = 7.
• D: H₂SO₄ is a strong diprotic acid, dissociates to [H⁺] ≈ 2M, pH < 0.

Final answer: C