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# Calculating pH, Ka, grams, and amounts of an acid for making a buffer

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1. Calculate the pH of a solution which is 0.428 M in oxalic acid and 1.44 M in oxalate.

2. What is the pH of a solution that is 45.5 mM in acetic acid and 1.11 M in acetate?

3. A solution which is 3.19X10 to the -3 M in an acid (HA) and 6.78x10 to the -3 M in its conjugate base (A-) is found to have a pH of 8.65. What is the Ka of the acid?

4. Calculate the number of grams of NaH2PO4 (MW=120.0) and the number of grams of Na2HPO4 (MW=142.0) that should be weighed out and dissolved to 1 L to give a 100 mM solution in total phosphate at pH=7.50.

5. Calculate the amounts of formic acid and formate that must be used to make 1 L of buffer at pH= 3.80 and that is 250 mM in total formic acid / formate.

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#### Solution Summary

This solution is provided in 805 words in an attached .doc file. It describes buffers and buffer systems, as well as pKa and the Hendersen-Hasselbalch equation.

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