So the formula for Kw becomes simply the hydronium ion concentration times the hydroxide concentration.

水分子既可以释放氢离子，也可以接收氢离子。

If you paid attention, you learned how pure water ionizes to form hydronium and hydroxide ions in reversible reactions.

也会出现0以下或是14以上的时候但那只会出现在一些极端条件下。

But we can also use the Kw and the hydronium ion concentration to do a very simple division problem and find the hydroxide concentration.

当氢离子浓度上升时pH值会降低举个例子，一种弱酸比方说醋酸，被加到水中时。