In: Chemistry
From the equilibrium concentrations given, calculate Ka for each of the weak acids and Kb for each of the weak bases.
c) HCO2H
[HCO2H]= 0.524 M
[H3O+]= 9.8 x 10^-3 M
[HCO2-] 9.8 x 10^-3
d) C6H5NH3+
[C6H5NH3+]= 0.233
[C6H5NH2]= 2.3 x 10^-3
[H3O+]= 2.3 x 10^-3
c) HCO2H
[HCO2H]= 0.524 M
[H3O+]= 9.8 x 10^-3 M
[HCO2-] 9.8 x 10^-3
Solution :-
HCO2H + H2O ----- > H3O+ + HCOO-
0.524 0 0
-x +x +x
0.524-x 9.8 x 10^-3 9.8 x 10^-3
Ka= [H3O+][HCOO-]/[HCOOH]
= [9.8*10^-3][9.8*10^-3]/[0.524-9.8*10^-3]
= 1.87*10^-4
d) C6H5NH3+
[C6H5NH3+]= 0.233
[C6H5NH2]= 2.3 x 10^-3
[H3O+]= 2.3 x 10^-3
C6H5NH3+ + H2O ------- > C6H5NH2 + H3O+
0.233 0 0
-x +x +x
0.233-x 2.3*10^-3 2.3*10^-3
Ka = [C6H5NH2][H3O+] /[C6H5NH3+]
= [2.3*10^-3][2.3*10^-3]/[0.233-2.03*10^-3]
= 2.29*10^-5
Kb= kw/ka
= 1*10^-14/2.29*10^-5
= 4.37*10^-10