Kw (Ionic Product Of Water Constant) Flashcards
What is the ionic product of water constant?
A type of equilibrium constant used for the dissociation of H2O molecules into H3O+ and OH-
How do we obtain the expression of Kw?
Kc =[H+] [OH-] / [H2O]
Multiply both sides by H2O
Kc x H2O = [OH-] [H+]
Kw is Kc x H2O
So Kw = [OH-] [H+]
What reaction do we use to find Kw?
H2O <——> OH- + H+
How does dissociation of water like this occur?
Anywhere where water is because water can act as a base or acid
1 water molecule acts as base and accepts H+ to form H3O+
1 water molecule acts as acid and donates H+ to leave behind OH-
Why is [H2O] not included in expression for Kw?
Such little water is actually dissociated so it remains same: forms part of the constant because it remains constant
Kw is constant at…
1 temperature
Units of Kw
Mol² dm⁻⁶
Pure water means…
[H+] = [OH-]