So kw in this case, when we talk about autoionization, is called the ionization constant for H 20. And this depends on temperature. And at 25 degrees Celsius, you should know that kw is 1.0 times ten to negative 14. Now, notice that our exponents here are one and one. That's because we have 1 mol and 1 mol. So, since we know our kw, and from experiments, we know that at a PH of seven, our concentration of hydronium is 1.0
times ten to negative seven.