The pH of a solution is 5. To this solution, acid was added so that its pH value becomes 2.0. The increase in H⁺ concentration is:

$\mathrm{pH}=-{\log }_{10}\left[{\mathrm{H}}^{+}\right]$

original pH = 5
Original [H⁺] = 10 − pH = 10⁻⁵ M
 New p^H= 2
 New [H⁺] = 10 − pH =10⁻² M
The increase in [H+] =10⁻² M−10⁻⁵ M​=9.99×10²≃1000 times