Consider the following titrations and approximate the pH of the solution inside
ID: 994635 • Letter: C
Question
Consider the following titrations and approximate the pH of the solution inside the flask at the following points. Titration of a weak acid with a strong base. (ex: acetic acid and sodium hydroxide) The initial pH (before adding any base). The pH at the equivalence point. The pH at the half-equivalence point (after adding half the volume of base needed to reach the equivalence point) The pH after the equivalence point. Titration of a weak base with a strong acid. (ex: sodium acetate and hydrochloric acid) The initial pH (before adding any acid). The pH at the equivalence point. The pH at the half-equivalence point (after adding half the volume of acid needed to reach the equivalence point) The pH after the equivalence point. Titration of a strong acid with a strong base. (ex: hydrochloric acid and sodium hydroxide) The initial pH (before adding any base). The pH at the equivalence point. The pH at the half-equivalence point (after adding half the volume of base nExplanation / Answer
I will help you with the first one and the last one. The second one is pretty similar to the first one but with the inversed data cause we are titrating the opposite.
Titrating a weak acid with a strong base:
a) as we are not adding any base yet, the pH of the solution is only the pH of the acid dissociated. pH of acids goes from 0 to 7 and pH for base goes from 8 to 14, 7 is neutral (like water). So, in an acidic solution with no base added, the pH will be below 7.
b) In the equivalence point all the moles of acid has reacted completely with the moles of the base added, at this point and beyong the base will be in excess, so the pH would have to be above 7.
c) at the half equivalence point, the half of moles of the acid has reacted. This half moles would be the moles of the products, therefore the ratio of moles of reactants and products will be 1, and the pH would be the same as the pKa.
d) After the equivalence point, the moles of OH are in excess, so the pH would have to be above 7.
In the titration of a weak base and a strong acid occurs the opposite, try to answer this yourself.
For a titration of both a strong acid and base:
i) Same as a weak acid, only acid is in solution so pH would have be below of 7.
j) As we are having two strong compounds, both of them dissociates completely in solution, so ath the equivalence point, the pH would be neutral, approx. 7.
k) At the half equivalence point, a strong acid does not have pKa, but as we are still with an excess of acid, the pH would have to be below 7 yet.
l) After the equivalence point, the base is in excess and all the acid has been consumed, so pH would be above 7.
Hope this helps