Question

In: Chemistry

Calculate the pH of a 0.340M NaO2CCO2H solution. pKa1 = 1.250 and pKa2 = 4.266. Apparently...

Calculate the pH of a 0.340M NaO2CCO2H solution. pKa1 = 1.250 and pKa2 = 4.266. Apparently the answer is 2.79 but can someone explain this?

a. -0.029

b. 3.38

c. 2.79

d. 4.89

e. 2.37

Solutions

Expert Solution

answer : e) 2.37

NaO2CCO2H <-----------------------> NaO2CCO2- + H+

0.34                                                             0                  0

0.34 - x                                                         x                   x

Ka2 = x^2 /0.34 - x

5.42 x 10^-5 = x^2 /0.34 - x

x = [H+] = 4.30 x 10^-3 M

pH = -log [H+] = -log (4.30 x 10^-3)

pH = 2.37


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