Question

Part A Calculate the pH in 0.020 M H2CO3 (Ka1=4.3×10−7; Ka2=5.6×10−11). Express your answer using two decimal places. pH = SubmitMy AnswersGive Up Part B Calculate the concentrations of all species present (H2CO3, HCO−3, CO2−3, H3O+ and OH−) in 0.020 M H2CO3. Express your answers using two significant figures. Enter your answers numerically separated by commas. [H2CO3], [HCO−3], [CO2−3], [H3O+] and [OH−] = M

Answer 1

part A)

H2CO3    -------------------> HCO3-   +   H+

0.020                                      0             0

0.02 - x                                   x              x

Ka1 = x^2 / 0.02 - x

4.3 x 10^-7 = x^2 / 0.02 - x

x = 9.25 x 10^-5

[H+] = 9.25 x 10^-5 M

pH = -log [H+] =-log (9.25 x 10^-5 )

pH = 4.03

Part B)

[H2CO3] = 0.020 M

[HCO3-] = 9.2 x 10^-5 M

[CO32-] = 5.6 x 10^-11 M

[H3O+] = 9.2 x 10^-5 M

[OH-] = 1.1 x 10^-10 M