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Buffer Activity
Purpose: The purpose of this activity is to introduce the concept of a buffer. Students will learn that a buffer is a system that resists a change in pH. 
 
Calculator skills: In doing this activity, students will learn to collect data as selected events, use the store run option under file, and learn that they can display two plots simultaneously (L2 and L3 versus L1) using EasyData.
 
Materials:
 
  • CBL2 system
  • TI-84
  • pH probe
  • 2 beakers (100 mL)
  • magnetic stirrer
  • wash bottle
  • tonic water
  • 1 M NaHCO3 solution
  • water
  • 1 M HCl in a labeled pipet
 
Overview: 
 
In this experiment, the pH will be monitored as five drops of 1M HCl are added drop by drop to a beaker of water. EasyData will be used to collect the data in the selected events format. After storing this run, the same procedure will repeated using 50 mL of a buffered solution (25 mL of tonic water and 25 mL of 1M NaHCO3). The plots will be compared to illustrate how a buffered solution resists a change in pH.
 
As an extension, students could be asked to repeat the process, substituting 1 M NaOH for the 1 M HCl.
 
Note: This activity serves to introduce the topic of buffers by allowing students to graphically visualize how resistant buffers are to changes in pH.  Students actually create a two component buffer consisting of H2CO3 and NaHCO3. With this knowledge, the teacher can build the concept of buffer consisting of a weak acid and weak base containing a common ion. This buffer system is of particular relevance since it is responsible for maintaining  pH stability in the blood.



E Saylor

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