Question

A certain weak acid, HA, has a Ka value of 7.4×10−7. Part A Calculate the percent ionization of HA in a 0.10 M solution. Express your answer to two significant figures and include the appropriate units. Part B Calculate the percent ionization of HA in a 0.010 M solution. Express your answer to two significant figures, and include the appropriate units.

Answer 1

part A)

Ka = 7.4 x 10^-7

   C = 0.10 M

x = [H+] = sqrt (Ka x C)

x = sqrt (7.4×10^−7 x 0.1)

x = 2.72 x 10^-4

percent ionization of HA   = (2.72 x 10^-4 ) x 100 / 0.1

                                       = 0.27%

part B)

x = sqrt (7.4×10^−7 x 0.01)

x = 8.60 x 10^-5

percent ionization   = 8.60 x 10^-5 x 100 / 0.01

                               = 0.86 %