Question

IV. Comparing Buffering Capacity

A. pH of Pure Water

i. Measure out 30.0 mL DI H2O into a beaker.

1. Calculate the expected pH of pure water. pH ________

2. Measured pH of pure water. pH ___3.88______

3. What is the percent error between the calculated and measured value? What are some of the possible sources of this error?

% error __________

B. pH of Water and Strong Acid

i. Measure out 30.0 mL DI H2O and 2.0 mL of 1.0 M HCl into a beaker.

1. Calculate the expected pH of this solution. pH _________

2. Measured pH of this solution. pH ___1.64______

3. What is the percent error between the calculated and measured value? What are some of the possible sources of this error?

% error ____

C. pH of Water and Strong Base

i. Measure out 30.0 mL DI H2O and 2.0 mL of 1.0 M NaOH into a beaker.

1. Calculate the expected pH of this solution. pH _________

2. Measured pH of this solution. pH __12.03_______

3. What is the percent error between the calculated and measured value? What are some of the possible sources of this error?

% error ____

D. pH of Buffer solution

i. Measure out 50.0 mL 1.0 M CH3COOH and 50.0 mL of 1.0 M NaCH3COO into a beaker.

1. Calculate the total volume. (include units) Vol __________

2. What is the concentration of acetic acid in this solution after mixing. (include units)

[CH3COOH] _________

3. What is the concentration of acetate ion in this solution after mixing. (include units)

[CH3COO-] ___________

4. Calculate the expected pH of this buffer solution. pH __________

5. Measured pH of this buffer solution. pH __4.56________

6. What is the percent error between the calculated and measured value? What are some of the possible sources of this error?

% error __________

E. pH of Buffer after the addition of the Strong Acid

Measure out 50.0 mL the buffer in part D and add 2.0 mL of 1.0 M HCl into a clean beaker.

1. Calculate the expected pH of this solution. pH _________

2. Measured pH of this solution. pH ____5.30_____

3. What is the percent error between the calculated and measured value? What are some of the possible sources of this error?

% error ____

F. pH of Buffer after the addition of the Strong Base

Measure out 50.0 mL the buffer in part D and 2.0 mL of 1.0 M NaOH into a clean beaker.

1. Calculate the expected pH of this solution. pH _________

2. Measured pH of this solution. pH _4.57________

3. What is the percent error between the calculated and measured value? What are some of the possible sources of this error?

% error ____