Problem: Potassium sorbate, KC6H7O2 (molar mass 150 g/mol) is commonly added to diet soft drinks as a preservative. A stock solution of KC6H7O2(aq) of known concentration must be prepared. A student titrates 45.00 mL of the stock solution with 1.25 M HCl(aq) using both an indicator and a pH meter. The value of Ka for sorbic acid, HC6H7O2, is 1.7 x 10-5.(a) Write the net ionic equation for the reaction between KC 6H7O2(aq) and HCl(aq).(b) A total of 29.95 mL of 1.25 M HCl(aq) is required to reach the equivalence point. Calculate [KC6H7O2] in the stock solution.

FREE Expert Solution

We are asked to determine the concentration of a stock solution of sorbic acid HC6H7O2 by first writing its net ionic reaction with HCl


Part A: Writing the net ionic equation

• Potassium sorbate, KC6H7O2 is an ionic compound which will dissociate into ions when in a solution:

          • Potassium K is from group 1A and will have +1 charge → K+

          • Sorbate is the deprotonated form of sorbic acid → C6H7O2-

• The dissociation of KC6H7O2 is:

          KC6H7O2(aq) → K+(aq) + C6H7O2-(aq)

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Problem Details

Potassium sorbate, KC6H7O2 (molar mass 150 g/mol) is commonly added to diet soft drinks as a preservative. A stock solution of KC6H7O2(aq) of known concentration must be prepared. A student titrates 45.00 mL of the stock solution with 1.25 M HCl(aq) using both an indicator and a pH meter. The value of Ka for sorbic acid, HC6H7O2, is 1.7 x 10-5.

(a) Write the net ionic equation for the reaction between KC 6H7O2(aq) and HCl(aq).

(b) A total of 29.95 mL of 1.25 M HCl(aq) is required to reach the equivalence point. Calculate [KC6H7O2] in the stock solution.

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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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