Diapositive PPT
K2 = [CO32-] [H3O+] / [HCO3-]
[CO32-] + [HCO3-] + [H2CO3] = C
[H3O+] + 2 C = [OH-] + 2 [CO32-] + [HCO3-]
2 C = [OH-] + [CO32-] + [CO32-] + [HCO3-]
2 C = [OH-] + [CO32-] + C
[HCO3-] = C - [CO32-] = C - C + [OH-] = [OH-] = w
K2 = [CO32-] [H3O+] / [HCO3-]
K2 = ( c- w )( Ke / w ) / w
10-10,3 = ( 0,025 - w )( Ke / w ) / w
Après résolution on trouve bien : pH = 11,33
(Équation du second degré en w)