Consider the K_a values for the following acids:
Cyanic acid,HOCN,3.5 $\times$ 10^-4
Formic acid,HCHO₂,1.7 $\times$ 10^-4
Lactic acid,HC₃H₅O₃,1.3 $\times$ 10^-4
Propionic acid,HC₃H₅O₂,1.3 $\times$ 10^-5
Benzoic acid,HC₇H₅O₂,6.3 $\times$ 10^-5
Which has the strongest conjugate base?

Question

Consider the K_a values for the following acids:
Cyanic acid,HOCN,3.5

\times

10^-4
Formic acid,HCHO₂,1.7

\times

10^-4
Lactic acid,HC₃H₅O₃,1.3

\times

10^-4
Propionic acid,HC₃H₅O₂,1.3

\times

10^-5
Benzoic acid,HC₇H₅O₂,6.3

\times

10^-5
Which has the strongest conjugate base?

Quizplus · Accepted Answer

The strength of a conjugate base is determined by its ability to stabilize the negative charge. This is directly related to the acidity of the corresponding acid, with stronger acids having weaker (more stable) conjugate bases. Looking at the given acids, HOCN has a KS1 value of 3.5, which is lower than all the other acids, indicating it is the strongest acid and therefore has the weakest (most stable) conjugate base. Benzoic acid has a KS1 value of 6.3, which is the highest among the given acids, indicating it is the weakest acid and therefore has the strongest (least stable) conjugate base. Among the remaining acids, lactic acid and propionic acid have the same KS1 value of 1.3, but lactic acid has a larger and more complex molecular structure, which makes it less likely to stabilize the negative charge compared to propionic acid. Therefore, the strongest conjugate base is associated with the acid HC₃H₅O₂, which is option D.

Consider the Ka Values for the Following Acids: Cyanic Acid,HOCN,3 ×\times×

Consider the K_a Values for the Following Acids:
Cyanic Acid,HOCN,3 $\times$