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.
So would you say that B is the correct answer.
yes
B. HCN Ka = 6.2 * 10^-10
just took the test
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.
To determine which acid has the strongest conjugate base among the given options, we need to compare their acid-dissociation constants (Ka) values. The higher the Ka value, the stronger the acid, and the weaker the conjugate base.
In this case, we are looking for the acid with the smallest Ka value since a smaller Ka indicates a weaker acid, which in turn means a stronger conjugate base.
Let's examine each option:
A. CH3COOH with Ka = 1.8 * 10^-5
B. HCN with Ka = 6.2 * 10^-10
C. HOCl with Ka = 3.0 * 10^-8
D. HIO3 with Ka = 0.17
Comparing these values, we can see that the Ka values become smaller in the order: HIO3 > CH3COOH > HOCl > HCN.
Therefore, option B (HCN) has the smallest Ka value, indicating that it is the weakest acid and, consequently, has the strongest conjugate base among the given options.