Multiple Choice
What is the pH of a 0.150 M solution of CH3COOH, given that the Ka of CH3COOH is 1.8 × 10⁻⁵?
17. Acid and Base Equilibrium
pH of Weak Acids
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What is the pH of a mixture of 200 mL of a 0.39 M solution of the weak acid hydronium ion (H₃O⁺) and 250 mL of a 0.62 M solution of hypoiodous acid (HIO, Kₐ = 2.3 × 10⁻¹¹)?
A
pH = 6.30
B
pH = 4.75
C
pH = 5.85
D
pH = 5.10
Verified step by step guidance1
Calculate the moles of H₃O⁺ in the 200 mL solution using the formula: moles = concentration × volume. Convert the volume from mL to L by dividing by 1000.
Calculate the moles of HIO in the 250 mL solution using the formula: moles = concentration × volume. Again, convert the volume from mL to L.
Determine the total volume of the mixture by adding the volumes of the two solutions (200 mL + 250 mL) and convert this total volume to liters.
Calculate the concentration of H₃O⁺ in the mixture by dividing the moles of H₃O⁺ by the total volume of the mixture in liters.
Use the Henderson-Hasselbalch equation to find the pH of the solution: pH = pKa + log([A⁻]/[HA]), where [A⁻] is the concentration of the conjugate base and [HA] is the concentration of the weak acid. Use the given Kₐ to find pKa: pKa = -log(Kₐ).
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