2015 AP Chemistry free response 3a | Chemistry | Khan Academy

TL;DR

This content explains how to write the net ionic equation for the reaction between potassium sorbate and hydrochloric acid.

Transcript

• [Voiceover] Potassium sorbate, and they give us its formula right over here, has a molar mass of 150 grams per mole. They put this decimal here to show us that these are actually three significant figures. Even the zero is a significant digit here. Is commonly added to diet soft drinks as a preservative. A stock solution of potassium sorbate, dis... Read More

Key Insights

• 🍦 Potassium sorbate is commonly used as a preservative in diet soft drinks.
• ❓ The concentration of a stock solution can be determined by titration.
• 😑 The net ionic equation only includes the ions that participate in the reaction.

Questions & Answers

Q: What is the purpose of potassium sorbate in diet soft drinks?

Potassium sorbate is added to diet soft drinks as a preservative to prevent the growth of bacteria, yeast, and molds, thus extending the shelf life of the product.

Q: How is the concentration of the stock solution of potassium sorbate determined?

The concentration of the stock solution is determined by titrating a known volume of the solution with a solution of known concentration, in this case, 1.25 molar hydrochloric acid, until the endpoint is reached.

Q: What is the difference between an ionic equation and a net ionic equation?

An ionic equation shows all the ions present in the reaction, both as reactants and products, whereas a net ionic equation only shows the ions that participate in the reaction.

Q: How is the net ionic equation for the reaction between potassium sorbate and hydrochloric acid written?

In the net ionic equation, only the ions that are involved in the reaction are shown. In this case, the C6H7O2- ion reacts with the hydrogen proton to form sorbic acid: HC6H7O2.

Summary & Key Takeaways

• Potassium sorbate is a compound used as a preservative in diet soft drinks.

• To prepare a known concentration of potassium sorbate, a student titrates 45 milliliters of the stock solution with 1.25 molar hydrochloric acid.

• The net ionic equation for the reaction between potassium sorbate and hydrochloric acid can be written as the C6H7O2- ion reacting with the hydrogen proton to form sorbic acid: HC6H7O2.