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ChemistryMediumMCQ2022 · 28 Jun Shift 2

Q35.A student needs to prepare a buffer solution of propanoic acid and its sodium salt with pH 4. The ratio of [CH3 CH2 COO−] required to make buffer is Given : Ka(CH3 CH2 COOH) = 1. 3 × 10−5 [CH3 CH2 COOH] (1) 0. 03 (2) 0. 13 (3) 0. 23 (4) 0. 33

What This Question Tests

This question applies the Henderson-Hasselbalch equation to calculate the required ratio of conjugate base to weak acid for a given pH and acid dissociation constant.

Concepts Tested

Henderson-Hasselbalch equationpH of buffer solutionAcid dissociation constant

Formulas Used

pH = pKa + log([Salt]/[Acid])

pKa = -log(Ka)

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