General Grading Items| 25 Points|
Attendance at Pre-lab Meeting| /10|
Copies of lab pages attached; labeled with name and date, complete information, readable, data recorded matches results given in report| /5| Waste was properly disposed of and lab area was cleaned| /5| Evaluation of student performance overall (student was on time, followed safety rules, performed the lab correctly and within the time allowed, etc)| /5| Total for General Grading Items| /25|
Data Analysis and Interpretation Part | 75 Points|
Titration Curves| /25|
Question 1| /15|
Question 2 | /15|
Question 3| /20|
Total for Data Analysis and Interpretation| /75|
| Buffer A| Buffer B|
Mass of NaC2H3O2 used to prepare buffer (grams)| | |
Volume of buffer prepared (mL)| 100.0| 100.0|
Molar concentration of HC2H3O2 in buffer (M)| 0.1| 1.0|
Initial pH of buffer| | |
Volume of 0.5 M NaOH to raise pH by 2 units (mL)| | |
Volume of 0.5 M HCl to lower pH by 2 units (mL)| | |
Volume of 0.5 M NaOH at equivalence point (mL)| | |
1. Write reaction equations to explain how your acetic acid-acetate buffer reacts with an acid and reacts with a base.
2. Buffer capacity has a rather loose definition, yet it is an important property of buffers. A commonly seen definition of buffer capacity is: “The amount of H+ or OH– that can be neutralized before the pH changes to a significant degree.” Use your data to determine the buffer capacity of Buffer A and Buffer B. (Graphically, we can identify buffer capacity by the sudden change to a very steep slope.)
3. Say, for example, that you had prepared a Buffer C, in which you mixed 8.203 g of sodium acetate, NaC2H3O2, with 100.0 mL of 1.0 M acetic acid.
a. What would be the initial pH of Buffer C?
b. If you add 5.0 mL of 0.5 M NaOH solution to 20.0 mL each of Buffer B and Buffer C, which buffer’s pH would change less? Explain.