Diluting Acid and PH Value

Diluting an acid or an alkali would change the pH of the solution,because the action of dilution (adding water) would change the concentration ofhydrogen ions of the solution.

Example 1 : Diluting a 0.1 M HCl solution to 0.01 M
pH before dilution = -log(0.1) = 1
pH after dilution = -log(0.01) = 2
Obviously, the pH of the solution is changed.

Example 1 : Diluting a 0.01 M HCl solution to 0.001 M
pH before dilution = 14 + log(0.01) = 12
pH after dilution = 14 + log(0.001) = 11
Obviously, the pH of the solution is changed.