The Chemistry texts I have present the ion-product constant as:
$$K_\mathrm w= 1.0 \times 10^{-14} = [\ce{H+}][\ce{OH-}]$$
Additionally I'm told that this constant at (25 °C) is an equilibrium. As one concentration rises, the other declines.
It seems easy to imagine a constant as a sum which the $[\ce{H+}]$ and the $[\ce{OH-}]$ concentrations add up to in a mixture but it's very difficult for me to grasp the idea that they are a product of multiplication.
What am I missing here?
