We know that
pH = -log[H+]
the pH value falls in between 0- 7 for acids
As the pH value increases the concentration of [H+] increases.
similarly as the value of pH approaches 0, the concentration of H+ increases
The solution said to become more acidic
Also
[H+] X [OH-] = 10^-14
Thus pH + pOH = 14
hence the concentration of OH- decreases as the pH approaches zero
