The pH of a solution is 4.0. What should be the change in the hydrogen ion concentration of the solution, if its pH is to be increased to 5.0.
As the pH value increases from 0 to 7, it represents a decrease in hydrogen ion concentration in the solution, that is, decrease in the strength of acid. Hence, when the pH = 4.0 is increased to 5.0, there is a decrease to 1/10 of its original concentration.