Purpose: This activity will involve measuring the pH of a set of juices in order to determine the concentration of hydronium ion in each. Measure the pH of five different solutions of juices. Manipulate the data to determine the amount of hydronium ion in each solution, [H₃O⁺¹].

Time required:  1 day.

Materials needed  per group:

• A set of five different juice solutions- cranberry, pineapple, grape juice, orange, apple
• 5 plastic cups for the solutions
• pH probe
• wash bottle
• one cup to serve as a waste receptacle

Prior knowledge: The student should be able to exponentiate a pH value using the following formula:

[H₃O⁺¹] = 10^-pH

Students should understand that a greater concentration of hydronium ion is associated with greater acidity. 

Procedure:

1. Students should work in groups of 2.
2. Obtain 5 cups, each containing approximately 10 mL of juice.
3. Using the pH probe, determine the pH of each solution. The pH of each solution will be recorded in the data table. The probe must be rinsed over the waste receptacle between measurements, using a wash bottle.
   
   

   type of juice
   pH of juice




4. The set of juices will be returned to the lab table to be used again by the next lab group.

Analysis: Using the pH, calculate the [H₃O⁺¹] in each of the juices.

type of juice
pH of juice
[H3O+1] Decimal form
[H3O+1] Scientific Notation

1. What is the relationship between the amount of [H₃O⁺¹] in a solution and the acidity of the juice?
2. What do all the juices have in common?
3. Create a graph with pH as the independent variable and concentration of H₃O⁺¹ as the dependent variable and use the statistics capabilities of a graphing utility to graph the data and find the best fitting exponential function.