P Soup

Objective: This activity will involve measuring the pH of a set of buffered solutions. Once the pH is determined, the concentration of the hydronium ion can be calculated.

Time required: 1 day.

• Measure the pH of five different solutions.
• Manipulate the data to determine the amount of hydronium ion in each solution, [H₃O⁺¹].

Group Size: 2 students

Materials Needed Per Group:

• A set of five different buffer solutions
• 5 plastic cups for buffers
• pH probe
• wash bottle
• one cup to serve as a waste receptacle

Prior Knowledge: The student should be able to exponentiate a number using the formula

          [H₃O⁺¹] = 10^-pH

1. Obtain 5 cups, labeled A, B, C, D, E. Each cup contains approximately 10 mL of buffer. Each of the five buffers has a different pH.




2. Using the pH probe, students will 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.
   
   

   Raw Data Table
   
   

   Solution	A	B	C	D	E
   pH

3. The set of buffers 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 buffers.

Processed Data Table

Solution	A	B	C	D	E
pH of Solution
[H3O+1] Decimal Form
[H3O+1] Scientific Notation

What is the relationship between the amount of [H3O+1 ] in a solution and the acidity of the solution?