Question

Using the K, values in the table below, calculate the pH of a buffer that contains the given concentrations of a weak acid and its conjugate base. 0.34 M NaHCO3 and 0.74 M Na2CO3 pH-

Answer 1

for a buffer

pH = log (ka) + log( [conjugate base / acid])

Ka for NaHCO3 = 5.6 x 10-11

given

[acid] = [NaHCO3] = 0.34 M

[conjugate base ] = [Na2CO3] = 0.74 M

so

pH = -log (5.6 x 10-11) + log ( 0.74 / 0.34)

pH = 10.59

so

pH of the buffer solution is 10.59