Question

Every change in one pH unit represents a change in [H+] and [-OH] by a factor of 10.

If the initial pH of a solution is 4.5, what will be the final pH after enough water is added to dilute the original concentration to 1% of its initial value?

Answer 1

Diluting a solution to 1% of its initial concentration reduces the hydrogen ion concentration by a factor of 100, corresponding to a two-unit increase in pH. If the initial pH is 4.5, the final pH after such a dilution will be 6.5.

Step-by-step explanation:

The question is focused on understanding how diluting a solution affects its pH level. To calculate the final pH after dilution, we need to recognize that each pH unit represents a tenfold change in hydrogen ion concentration [H⁺].

If the initial concentration of a solution is reduced to 1% of its value, this implies that the hydrogen ion concentration is also reduced to 1%, which is the same as saying that the [H⁺] has been reduced by a factor of 100, or 102.

Since a change of one unit on the pH scale corresponds to a change in the concentration of hydrogen ions by a factor of 10, reducing the hydrogen ion concentration by a factor of 100 will increase the pH by 2 units.

Hence, if the initial pH of the solution is 4.5, after dilution to 1% of its initial concentration, the final pH will be 4.5 + 2 = 6.5.