[lha08]

i was wondering if anyone knows why water is ignored when applying Kc? Thanks.
H2O+H2O=H+OH
Kc=[H][OH]

[ARGOS++]

Dear lha08;

It is not ignored but contain in K_c for practical use, because [H₂O ] is very constant ( = 55.55 molar), in the following sense:
        [H⁺] [OH^-] / [H₂O ] = K’_c    ===>  [H⁺] [OH^-]  = K’_c  * [H₂O ]   =  K_c

[edit]:  You may also read:   http://www.chembuddy.com/?left=pH-calculation&right=water-ion-product

Good Luck!
                    ARGOS⁺⁺