The acid dissociation constant, Ka, for this reaction is given by the following formula (this is also in your book):
Ka=[H3O+][A−][HA]
The acid concentration, [HA] is given in the introductory information of this problem. Using this information and your answers from the previous two questions, calculate Ka for this acid.
I suggest you read these things before you post them. You provided absolutely no information other than it is in the introductory information. But I don't see any introductory information.
To calculate the acid dissociation constant (Ka) for the given reaction, you need the concentration of the hydronium ion ([H3O+]), the concentration of the conjugate base ([A-]), and the concentration of the acid ([HA]).
Given that the acid concentration ([HA]) is provided in the introductory information, you can use it directly in the Ka formula. However, if the concentrations of [H3O+] and [A-] are not given, you will need additional information to calculate them.
To determine the concentrations of [H3O+] and [A-], you need to understand the nature of the acid and its dissociation process. If the acid is monoprotic (donates only one proton), then the concentration of [H3O+] and [A-] will be the same as the concentration of [HA].
However, if the acid is polyprotic (donates multiple protons), or if the acid dissociation reaction is not complete, then you may need additional information, such as the pH of the solution, or the percentage dissociation of the acid, to determine the concentrations of [H3O+] and [A-].
Once you have the concentrations of [H3O+], [A-], and [HA], you can substitute them into the Ka formula and calculate the acid dissociation constant (Ka).