How much more acid is a solution of pH 6 from a solution oh pH 9?

A solution with a pH of 6 is ten times more acidic than a solution with a pH of 7, and a solution with a pH of 9 is ten times less acidic than a solution with a pH of 8. Therefore, the difference between pH 6 and pH 9 is three pH units, indicating that the pH 6 solution is 1,000 times more acidic than the pH 9 solution. This is because each pH unit represents a tenfold change in hydrogen ion concentration.