Question

This is in regards to a titration lab and how dilution would affect certain aspects of it. I know that the initial unknown acid solution which has been diluted would have a higher pH, but a little confused about the remaining parts. Thanks for your help!

Consider if the initial unknown acid solution used in this experiment started out more dilute. Predict any differences you would expect to see in the titration curve ‐ clearly identify what changes, if any, are expected for:  

a. initial pH

b. pH at the half‐equivalence point

c. NaOH volume needed to reach the equivalence point

d. pH at the equivalence point  

Answer 1

(a) If the solution is more dilute the initial pH will be more. Because as the concentration is lowered the H+ concentration will decrease.

(b) pH at the half equivalenc point will also be more.

(c) The volume of NaOH needed to reach the equivalence point will be less. Because there are less H+ ions in dilute solution hence less OH- ions will be required for neutralisation.

(d) There will be NO effect on pH at the equivalence point. Because there will be equal amount of H+ and OH- ions at equivalence point irrepective of whether the solution is dilute or concentrated.