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.

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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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Problem Details

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.

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Equivalence Point concept. If you need more Equivalence Point practice, you can also practice Equivalence Point practice problems.

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