Determine the pH of a KOH solution made by mixing 0.251 g KOH with enough water to make 1.0 × 10² mL of solution. A)1.35 B)2.35 C)7.00 D)11.65 E)12.65

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Quizplus · Accepted Answer

KOH is a strong base and dissociates completely in water. First, calculate the molarity of the KOH solution:  Molar mass of KOH = 39.10 (K) + 16.00 (O) + 1.01 (H) = 56.11 g/mol.  Moles of KOH = 0.251 g / 56.11 g/mol = 0.00447 mol.  Volume of solution = 100 mL = 0.1 L.  Molarity (M) = 0.00447 mol / 0.1 L = 0.0447 M.  Since KOH is a strong base, [OH⁻] = 0.0447 M.  pOH = -log(0.0447) ≈ 1.35.  pH = 14 - pOH = 14 - 1.35 = 12.65.

Determine the PH of a KOH Solution Made by Mixing