Answer :
Final answer:
In the presence of 0.01 M HCl, the degree of dissociation of 0.01 M acetic acid is markedly suppressed due to the common ion effect, making option A (1.69 x 10⁻⁷) the most appropriate answer from the choices provided.
Explanation:
The degree of dissociation of 0.01 M acetic acid in the presence of 0.01 M HCl can be found by considering the dissociation constant (Ka) of acetic acid and the fact that HCl is a strong acid that will dissociate completely in solution.
Given that the Ka of acetic acid is 1.75 x 10-5, which is very small, this indicates there will be much more acetic acid undissociated in solution than dissociated.
However, because HCl completely dissociates, adding 0.01 M HCl to the solution will suppress the dissociation of acetic acid by the common ion effect, and therefore, the degree of dissociation of acetic acid will be even less than if it were alone.
The presence of a common ion (H+ from HCl) will significantly decrease the dissociation of acetic acid because the reaction is shifted to the left according to Le Chatelier’s principle.
With a smaller degree of dissociation, will be significantly lower than if acetic acid were alone in solution. Hence, option A (1.69 x 10-7) is the most suitable answer given the choice of answers provided.
