Which of the following has the strongest conjugate base? A. O cyanic acid, K = 3.510^4 B. O chlorous acid, K = 1.110^-1 C. O hypobromous acid, K = 2.810^-9 D. O acetic acid, K = 1.810^-5
The Correct Answer and Explanation is:
The strongest conjugate base is associated with the acid that has the smallest acid dissociation constant (Kₐ), because the weaker the acid, the stronger its conjugate base.
Let’s analyze the options based on the given Kₐ values:
A. Cyanic acid (Kₐ = 3.5 × 10⁴)
This is a strong acid with a very high Kₐ value. A stronger acid has a weaker conjugate base, so cyanate (the conjugate base of cyanic acid) would be weaker.
B. Chlorous acid (Kₐ = 1.1 × 10⁻¹)
This has a moderate Kₐ value. While it is weaker than cyanic acid, the conjugate base here (chlorite) is still not the strongest.
C. Hypobromous acid (Kₐ = 2.8 × 10⁻⁹)
Hypobromous acid is a weak acid with a very low Kₐ value, indicating it does not dissociate much in solution. This means the conjugate base (hypobromite) will be stronger.
D. Acetic acid (Kₐ = 1.8 × 10⁻⁵)
Acetic acid is also a weak acid, with a relatively higher Kₐ compared to hypobromous acid. Its conjugate base (acetate) is stronger than that of cyanic or chlorous acid but weaker than hypobromite.
Correct answer:
C. Hypobromous acid
Because it has the smallest Kₐ, hypobromous acid is the weakest acid in this list, and its conjugate base (hypobromite) is the strongest. In general, the stronger the acid, the weaker the conjugate base, and the weaker the acid, the stronger the conjugate base.
