Question

Calculate the pH of a buffer that is 0.230M in NaHCO3 and 0.310M in Na2CO3

Express your answer using two decimal places

Answer 1

The K_a2 for carbonic acid is 5.62 x 10^-11

According to Henderson's Equation

Given [salt] = [Na₂CO₃]=0.310 M

        [acid]=[NaHCO₃]=0.230 M

       K_a of HCO₃^- is 5.62 x 10^-11

pK_a = -log K_a

      = - log (5.62 x 10^-11)

     = 11 - log 5.62

     = 10.25

Plug the values we get

                                pH = 10.38