4. During a practical exercise, you find out that you need to adjust the pH of a strong acidic solution of volume 5.6 litres from 4.52 to 5.25

Question

(i) What would you add, OH- or H3O+ to adjust the pH? Explain your answer.
(ii) Assuming that there is a negligible volume change, how many moles of OH- or H3O+ must be added to bring about the adjustment.

Answer 1

i. From 4.52 to 5.25 is going to more basic solution so you will need to add >>>>>>>?
ii. Convert pH 4.52 to H^+. Convert pH 5.25 to H^+. Subtract to find the difference (which will be in units of moles/L) and multiply that difference by 5.6 L (that's the volume you have to work with). That will give you moles of what must be added.

Answer 2

1.4 * 10^-4 moles OH-