What we must do is convert from this guy to the exponent form because we have the base x, we have the y, the e to exponent. Now we have x to the e, plug that into the calculator and we get our y. And this is exactly what we do in part one. So in part one, let's first write down our formula for PH. We know PH is equal to the negative log of our hydronium concentration. But that's the same thing as saying negative log of the hydride ion concentration.