WAEC Chemistry 2016 Paper

Concept:Acidic solutions have $\mathrm{pH} < 7$. When an acidic solution is diluted, $[\mathrm{H}^+]$ decreases, so the $\mathrm{pH}$ increases toward neutrality.Explanation:M has $\mathrm{pH} = 2$ and N has $\mathrm{pH} = 6$, so both are acidic.Q has $\mathrm{pH} = 8$ and R has $\mathrm{pH} = 11$, so both are alkaline.M is the most acidic solution, while R is the most alkaline solution.Therefore, options C and D are incorrect.Since N is acidic, diluting its solution reduces $[\mathrm{H}^+]$.A lower $[\mathrm{H}^+]$ results in a higher $\mathrm{pH}$.So the $\mathrm{pH}$ of N is increased when the solution is diluted.Option B cannot be safely concluded from the given information alone.Answer:A. The $\mathrm{pH}$ of N is increased when the solution is diluted