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In this lab, you will be making an acid buffer. The buffer will be composed of 0.10M acetic acid solution and salt of its conjugate base (sodium acetate).
Pre-lab directions
1. On a separate sheet of paper (either in your lab notebook or an piece that you will put in your lab notebook), determine how many grams of sodium acetate you need to obtain a 0.10M sodium acetate solution.
2. Write the chemical reaction of acetic acid and water including the products.
Directions
1. Get a pH probe system and make sure it has been calibrated by your teacher.
2. Place 100mL of DI water into a 250.mL beaker.
3. Using the pH probe, determine the DI water pH. Record.
4. Before entering lab, you determine the mass of sodium acetate you needed to add the 100.mL of DI water to get a 0.10M sodium acetate solution. You will weigh out that amount of the salt and add it to the solution. Stir until all salt is dissolved. (Note: you used the 0.10M acetic acid solution to dissolve the salt instead of using DI water).
5. Use the pH probe to determine the pH of the new solution. (Note: This is the acid buffer so if a strong base is added, the pH would not change significantly.)
6. Using the 0.10M sodium hydroxide solution, add 2 drops of this solution into the buffer solution. Record new solutions pH. Repeat 2 more times. If the pH has not change significantly (i.e. from pH =4.32 to pH=9.05), then keep on adding drops of strong base until it does. Record total number of drops of strong base added and the final pH of the solution.
7. Using DI water, rinse off pH probe and put back into storage solution.
8. Dispose of all solutions into sink except for the 0.10M sodium hydroxide solution. Rinse all glassware and put into drying rack/bucket.