Chemistry Practice Problems Equivalence Point Practice Problems Solution: A 0.552-g sample of ascorbic acid (vitamin C) was ...

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Solution: A 0.552-g sample of ascorbic acid (vitamin C) was dissolved in water to a total volume of 20.0 mL and titrated with 0.1103 M KOH, and the equivalence point occurred at 28.42 mL. The pH of the solution at 10.0 mL of added base was 3.72.Determine Ka for vitamin C.

Problem

A 0.552-g sample of ascorbic acid (vitamin C) was dissolved in water to a total volume of 20.0 mL and titrated with 0.1103 M KOH, and the equivalence point occurred at 28.42 mL. The pH of the solution at 10.0 mL of added base was 3.72.

Determine Ka for vitamin C.

Solution

We are being asked to calculate the Ka at the equivalence point in the titration ascorbic acid (Vitamin C) with KOH.


We will calculate the pH of the solution at the equivalence point using the following steps:

Step 1. Calculate the initial amounts of ascorbic acid and KOH in moles before the reaction happens.
Step 2. Calculate the concentration of ascorbic acid and KOH in moles at pH 3.72.
Step 3. Calculate Ka.


Step 1. Calculate the initial amounts of ascorbic acid and KOH in moles before the reaction happens.

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