Diapositive PPT
2) Si pK1 + pK2 < 14 : la solution est trop acide pour pouvoir négliger [H3O+]
E.N : [OH-] + [AH-] + 2 [A2-] = [H3O+ ] + C0
C.M.1 : [AH2] + [AH-] + [A2-] = C0
E.N - CM1 : [AH-] + 2 [A2-] - [AH2] - [AH-] - [A2-] = [H3O+]
soit : [A2-] - [AH2]= [H3O+]
K1 = [AH-] [H3O+] / [AH2]
K2 = [A2-] [H3O+] / [AH-]
[AH2] = [AH-] [H3O+] / K1
[A2-] = K2 [AH-] / [H3O+]
K2 [AH-] / h - [AH-] h / K1= h
AH- reste néanmoins dans la plupart des cas très largement majoritaire et on peut donc poser [AH-] = C