A 25.0 mL sample of 0.723 M HClO₄ is titrated with a 0.27 M KOH solution. The H₃O⁺ concentration after the addition of 80.0 mL of KOH is ________ M. A)0.4 B)1 × 10^-7 C)0.7 D)3 × 10^-13 E)4 × 10^-2

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Quizplus · Accepted Answer

The moles of HClO₄ initially present are 0.018075 mol. The moles of KOH added are 0.0216 mol. KOH neutralizes HClO₄, leaving an excess of 0.003525 mol of OH⁻. The concentration of OH⁻ is 0.03525 M, and the concentration of H₃O⁺ is 1 × 10⁻¹⁴ / 0.03525 = 2.84 × 10⁻¹³ M, which is approximately 3 × 10⁻¹³ M.

A 250 ML Sample of 0