Question

Which acid dissociation constant (ka) indicates the weakest acid answers?

Answer 1

The weakest acid is indicated by the smallest Ka value. A lower Ka means the acid is less ionized in solution, reflecting weaker acidity.

Step-by-step explanation:

The acid dissociation constant (Ka) indicates the strength of an acid in solution. The smaller the Ka value, the weaker the acid. For a series of acids with given Ka values, the weakest acid is the one with the smallest Ka number. This indicates that the acid is less ionized in solution compared to acids with larger Ka values. In other words, acids with lower Ka values are weaker because there is a lower concentration of hydronium ions in solution.

For example, consider the following Ka values: A. 6.6 × 10-4 B. 4.6 × 10-4 C. 9.1 × 10-8 D. 3.0 × 102. To rank these from the strongest to the weakest acid, we would list them as D, A, B, C, with acid C being the weakest due to its smallest Ka value.

Answer 2

The dissociation constant Kₐ for an acid [HA] is written as,

Kₐ = [H⁺] [A⁻] / [HA]

It is the ratio of dissociated Ions to undissociated acid. Means, Kₐ represents the extent of Ionization of an Acid. Greater the value of Kₐ, greater will be the dissociation, greater will be the production of H⁺ and greater will be the strength of an acid.

Examples:

Kₐ of Strong Acid HI = 3.2 × 10⁹

Kₐ of Weak Acid CH₃COOH = 1.8 × 10⁻⁵