So if we know what the PH is, then we can easily calculate what the concentration of the hydrogen ion in solution is. For example, if you know that the PH is equal to seven at room temperature. Then you can use this and a bit of algebra to calculate what the concentration is. So if the PH is equal to seven, we set the left side of the equation equal to seven. And then we solve for the hydrogen ion concentration. So we essentially take the negative side.