Question

Calculate the concentration of all species in a 0.130M solution of H2CO3. [H2CO3], [HCO3^-] , [CO3^2-], [H3O^+], [OH^-]

Please show work

Answer 1

Ka1   = 4.3*10^-7

Ka2   = 4.8*10^-11

         H2CO3 + H2O ---------------------> H3O^+ (aq) + HCO3^- (aq)

I        0.13                                                   0                        0

C      -x                                                       +x                       +x

E     0.13-x                                                  +x                       +x

                       Ka1   = [H3O^+][HCO3^-]/[H2CO3]

                        4.3*10^-7   =   x*x/0.13-x

                       4.3*10^-7*(0.13-x)   = x^2

                            x   = 0.00024

                   [H3O^+]   = x   = 0.00024M

                  [OH^-]     = Kw/[H3O^=]

                                  = 1*10^-14/0.00024    = 4.16*10^-11M

                  [HCO3^-]   = x = 0.00024M

              HCO3^- (aq) + H2O -------------------> CO3^2- (aq) + H3O^+ (aq)

                 Ka2    = [CO3^2-][H3O^+]/[HCO3^-]

                 4.8*10^-11   = [CO3^2-]*0.00024/0.00024

               [CO3^2-]      = 4.8*10^-11 M