So we know if this is equal to this, then this is a neutral solution. But an acidic solution is a solution in which this concentration is greater than this concentration. Now for example, let's suppose we know that the concentration of the H plus ion of our solution is equal to 1.0 times ten to negative six. The question is what exactly is the PH of this solution? Well, to find the PH, we use equation A. So the PH is equal to the negative log of the concentration of that hydrogen ion which is ten to negative six.