This activity is a fast and safe microscale experiment which allows students to quickly determine the molariy of three weak acids (vinegar, soda, and citric acid). Since the process involves a monoprotic, diprotic, and a triprotic acid, students recieve good exposure to the stoichiometry involved in titration calculations. By determining the pH of each solution at the endpoint, students learn that a neutralized solution is not necessarily neutral.
Before the Activity
1. Prepare pipets by printing out labels (see attached file) cutting them out and then taping the labels onto plastic pipets.
2. Prepare the solutions.
0.1 M NaOH- Dissolve 1.0 g of NaOH into 250 mL of distilled water.
0.1 M citric acid- Dissolve 4.8 g of anhydrous citric acid into 250 mL of water (You may also use hydrated citric acid, but adjust the amount of solute accordingly).
Soda- Use any type of clear carbonated beverage
Vinegar- Use any type of clear, household vinegar
Phenolphthalein- Use a prepared solution or dissolve 0.1 g of powder into a mixture of 50 mL of water and 50 mL of ethanol.
During the Activity
Distribute the pages of the activity to students.
After the Activity
Go over the results of the experiment, including the calculations.