CHEM1116-01-F15 Extra Credit Assignment Due by: 12/14/15
This assignment is an optional assignment. Skipping this assignment will not hurt your grade in any way. Each student
must work on this assignment independently, no assistance of any kind is allowed. Successful completion of the
assignment, in its entirety, is worth up to 5 extra credit points applied to your final course average.
Your mission, should you choose to accept it, is to describe how you would prepare a buffer with a pH and volume equal
to specific values from your birthdate. Using the format MM/DD/YY, your pH value will be equal to MM.DD, and the
required volume is YY mL.
For example, my birthdate is December 11, 1989, or 12/11/89. I would need to create a buffer with a pH of
12.11, at a volume of 89 mL.
Please answer the following questions, showing all work and explaining all answers. I am grading this based on the work
and explanations you provide; merely giving me an answer will not suffice.
1.) What is your birthdate, in MM/DD/YY format? (No explanation necessary.)
2.) What conjugate acid/base pair (from those options below) will work best for your buffer? Explain.
3.) What is the necessary mass of conjugate base (assume a sodium cation if necessary) that must be added to a 1.0 M
solution of your acid? (Show calculations.)
4.) Describe the steps that would be taken to physically create your buffer. (Check the textbook for examples.)
5.) What would the pH of your buffer be upon adding 0.005 moles of HCl? What would it be after the addition of 0.005
moles of NaOH? (Show calculations.)
You must select an acid/base pair from the following table. Although other pairs exist that may be a better fit, you are
limiting to selecting from the following.
Acid (Formula) Base (Formula) pKa
EDTA (C10H16N2O8) NaC10H15N2O8 1.78
Hydrofluoric acid (HF) NaF 3.45
Malonic acid (C3H4O4) NaC3H3O4 5.69
Hydrogen sulfide (H2S) NaHS 7.04
Hydrocyanic acid (HCN) NaCN 9.31
Hydrogen peroxide (H2O2) NaHO2 11.62
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