JAMB Chemistry 2023 Paper

Concept:Diluting an acidic solution lowers the concentration of hydrogen ions in the solution.Explanation:An acid produces hydrogen ions, written as $\mathrm{H^+}$, when dissolved in water.The pH of a solution measures its acidity using the formula $\mathrm{pH} = -\log[\mathrm{H^+}]$.When extra water is added during dilution, the amount of $\mathrm{H^+}$ stays constant.However, the total volume of the solution increases, so the concentration $[\mathrm{H^+}]$ decreases.Because pH is inversely related to $[\mathrm{H^+}]$, a smaller hydrogen ion concentration gives a larger pH value.For instance, if $[\mathrm{H^+}]$ drops from $10^{-3}$ to $10^{-4}$, the pH rises from 3 to 4.Therefore, the solution becomes less acidic and its pH moves closer to 7.Answer:It increases, so the correct option is D.