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。

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。