 | Sample Lab Questions Investigation #23:
"The NH3/NH4Cl Buffer System"
|
Click HERE for an overview of Investigation 23, compliments of Mr. Alex Redd.
These questions have been taken from lab quizzes given in previous years.
Some of the answers are listed at the end.
Note: The subscripts and superscripts may not appear as such. It depends upon your web browser.
- 1.
- a. (1pt) Of what does a buffer consist?
- b. (2pts) What are two characteristics of a buffer?
- 2.
- (1pt) Give an example of a buffer solution in the acidic region.
- 3.
- Given an ammonia buffer solution A that is 0.005 M in NH4+ and 0.001 M in NH3 and another ammonia buffer solution B that is 0.0005 M in NH4+ and 0.0001 M in NH3, answer the following:
- a. (1pt) Is the pH for both solutions the same or different? Why?
- b. (1pt) Is the buffer capacity the same for both solutions? Why or why not?
- 4.
- a.(3pts) A buffer solution was made by mixing 10.0 mL of 0.20 M NH3, 4.0 mL of 0.20 M HCl, and 6.0 mL of H2O. Calculate the concentrations of NH3 and NH4+ in this solution.
- b. (1pt) Determine the pH of this buffer solution. The Kb for ammonia is 1.8 x 10-5.
- 5.
- (2pts) A buffer undergoes a pH change from 4.5 to 5.1 when 32.0 mL of 0.15 M NaOH is added to it. Calculate the buffer capacity.
Answers
| 4. | a. | [NH4+] = 0.040 M
[NH3] = 0.060 M |
| b. | pH = 9.44 |
| 5. | | BC = 0.008 mol/ pH |
To report any corrections, please e-mail Dr. Wendy Keeney-Kennicutt.