Question
Given the following acid-dissociation constants, which acid has the strongest conjugate base?
A. CH3COOH Ka = 1.8 * 10^-5
B. HCN Ka = 6.2 * 10^-10
C. HOCl Ka = 3.0 * 10^-8
D. HIO3 Ka = 0.17
I'm not really sure how to approach this problem. Can someone please help me out.
A. CH3COOH Ka = 1.8 * 10^-5
B. HCN Ka = 6.2 * 10^-10
C. HOCl Ka = 3.0 * 10^-8
D. HIO3 Ka = 0.17
I'm not really sure how to approach this problem. Can someone please help me out.
Answers
DrBob222
The bottom line is that the strongest acid has the weakest conjugate base or the weakest acid will have the strongest conjugate base. The weakest acid must be HCN so CN^- should be the strongest base.
If you go another route, you can calculate Kb.
Kb = Kw/Ka. You can calculate Kb for each of the acids listed. You see that plugging in the smallest value for Ka gives you the largest base.
If you go another route, you can calculate Kb.
Kb = Kw/Ka. You can calculate Kb for each of the acids listed. You see that plugging in the smallest value for Ka gives you the largest base.
Edward
So would you say that B is the correct answer.
DrBob222
yes
Kattrina
B. HCN Ka = 6.2 * 10^-10
just took the test
just took the test