Question

3.

a. What concentration of acetic acid will have a pH of 2.50? pKa = 4.76

b. What concentration of oxalic acid, shown below, will have a pH of 2.50? pKa1 = 1.25, pKa2 = 4.14

c. One way oxalic acid can be produced in fungi is by hydrolysis of oxaloacetate, an intermediate in the Kreb’s citric acid cycle, to produce oxalic acid and acetic acid. This reaction, shown below, is catalyzed by oxaloacetase.

[O2CC(O)CH2CO2] 2− + H2O → C2O2− 4 + CH3CO− 2 + H+

In a 1-ml reaction mixture containing 50 mM NaCl, 50 mM HEPES, pH 7.8, 5 mM oxaloacetate and 5 pmol oxaloacetase, complete hydrolysis of the oxaloacetate was achieved in 10 minutes of incubation at 30°C. What was the pH of the reaction mixture at the end of the reaction?

Answer 1

Note: For 3(c) without calculation one can say that due to use of buffer, pH of the solution will remain equal to pH of within + 0.01 or -0.01 unit. But only for understanding I have done all the calculation.

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