I think that this:
Kw = [H+][OH-] = [H+]2
should be rewritten as:
and the Keq
value should be 1.8e-16
is 1.0e-14 at 25ºC (actually at 24ºC if i remember right, but 25ºC it's the standard temperature, so as it's almost equal with a change of only 1º we use the same value) and increases with temperature as the autoprotolysis of water is an endergonic reaction so it's favored by the rise of temperature.
Moreover we omit water only when we work with reactions in which this value is big enough that we can forget it, but removing water here makes the whole expression senseless (we have ions produced from what?) so we need to find out what's the concentration of the acid and basic ions in standard conditions in a neutral solution (1.0e-7) and that's just what Kw
tells us if [H+
] the solution is acidic, while if [OH-
] it's basic, but the value of Kw
is always the same.
Just another note... being more precise (nay correct) H+
should be written as H3
as you won't find protons alone in a watery solution but only in this form