if you want to prepare a buffer at pH = 5.2 which buffer would
you choose?
a) MES --> Ka = 7.9 x 10^-7
b) CHES --> Ka = 5.0 x 10^-7
c) Tris --> Ka = 6.3 x 10^-9
d) acetic aid --> Ka = 1.8 x 10^-5
Which equation can be used to find the pH of a buffer. Then
calculate the pH of a buffer containing 0.20 M CH3COOH and 0.20 M
CH3COONa. What is the pH after adding 10.0 mL of 0.10 M HCl to 65.0
mL of the buffer?
A common buffer used in biochemistry is a pH 7.4 phosphate
buffer. Such a buffer costs $53.00 for 100.00 mL from a common
chemical supply house. Therefore, it is useful to know how to
prepare such a buffer yourself! Imagine that you have available 0.1
M KH2PO4 and solid K2HPO4. Describe in detail how you would prepare
100.00 mL of a pH 7.4 phosphate buffer using these two reagents.
**Hint: You need to identify what is your acid and what...
You have the following solutions at your disposal to prepare a
buffer solution with a pH greater than 7.0:
(1) 50.0 mL of 0.35 M NH3 Kb = 1.8×10-5 (2) 55.0 mL
of 0.35 M NaOH
(3) 50.0 mL of 0.35 M HCl (4) 16.5 mL of 0.35 M NaCl NaOH
(5) 16.5 mL of 0.35 M HNO3 (6) 16.5 mL of 0.35 M KOH
(a) Assuming that you are going to mix the entire quantity of
the listed solutions to...
9)
You wish to prepare a buffer which has a pH of 4.9. Choosing among
benzoic acid/benzoate (Ka for benzoic acid is 6.28 × 10−5),
chlorous acid/chlorite (Ka for chlorous acid is 1.12 × 10−2), and
hypobromous acid/hypobromite (Ka for hypobromous acid is 2.3 ×
10−9), and assuming you want to prepare 1 L of this buffer and you
wish to have the buffer 0.25
M
with respect to the acid, what mass of the sodium salt of its
conjugate...
8) You wish to prepare a buffer which has a pH of 4.9.
Choosing among benzoic acid/benzoate (Ka for benzoic acid is 6.28 ×
10−5), chlorous acid/chlorite (Ka for chlorous acid is 1.12 ×
10−2), and hypobromous acid/hypobromite (Ka for hypobromous acid is
2.3 × 10−9), and assuming you want to prepare 2 L of this buffer
and you wish to have the buffer 0.3
M
with respect to the acid, what mass of the acid will be
necessary to...
Describe how you would prepare each of the following:
100.0 mL of a buffer with pH 7.4 using species from the
ionizations of phosphoric acid.
100.0 mL of a buffer with pH 7.4 using species from the ionizations
of carbonic acid.
Will these buffers be more effective against added acid or added
base?
You wish to make a buffer with a pH of 11.
A) Which of the following amino acids would you use to make your
buffer: glutamine, aspartate, histidine, or tyrosine?
B) Why would your chosen amino acid be better than the
others?
C) Start with 0.02M of the base form of your amino acid and
calculate the concentration of the acidic form needed to have your
buffer at the desire pH of 11. Show your work.
This is the third...
You wish to make a buffer with a pH of 11.
A) Which of the following amino acids would you use to make your
buffer: glutamine, aspartate, histidine, or tyrosine?
B) Why would your chosen amino acid be better than the
others?
C) Start with 0.02M of the base form of your amino acid and
calculate the concentration of the acidic form needed to have your
buffer at the desire pH of 11. Show your work.
PART I – Prepare a buffer and check the final pH using a pH
meter Material notes:
Sodium phosphate, monobasic, NaH2PO4·H2O (Mw = 138)
Sodium phosphate, dibasic-pentahydrate, Na2HPO4·7H2O (Mw = 268) pH
meter – calibrated using pH 4, 10, 7 reference buffers (done by
TA’s)
Special safety notes:
Wear your personal protective equipment (PPE).
Procedure
1. Calculate the amounts of weak acid and conjugate base
required to make 50 ml of 0.25 M solutions of each.
2. Prepare 0.25 M...