Step-by-step explanation:
We know that the relation between pH and concentration of hydrogen ions is as follows.
pH =
![-log [H^(+)]](https://img.qammunity.org/2020/formulas/chemistry/high-school/gopcqwordys161r0cdra5oyonsnub5hpxq.png)
or, pH =
![log (1)/([H^(+)])](https://img.qammunity.org/2020/formulas/chemistry/high-school/bjt3orjpnmrbeqld44jlb29ozjpln71e96.png)
As, pH is inversely proportional to the concentration of hydrogen ion. So, a decrease in the pH value will lead to an increase in tenfold (10X) compared to what it was at pH 9.
Thus, we can conclude that if the pH of a solution is decreased from 9 to 8, it means that the concentration of H has increased tenfold (10X) compared to what it was at pH 9.