Question

List the factors on which the \(K_{\mathrm{a}}\) of a weak acid depends.

Short answer

The factors influencing the \(K_{\mathrm{a}}\) of a weak acid include temperature, inherent strength of the acid, and type of solvent used.

Step-by-step solution

Factor 1: Temperature

Temperature is a significant factor affecting the \(K_{\mathrm{a}}\) of a weak acid. Factors affecting chemical equilibrium, such as the \(K_{\mathrm{a}}\) value, are themselves influenced by temperature. Generally, a rise in temperature will cause an increase in the \(K_{\mathrm{a}}\) value of a weak acid, thus enhancing the ionization of the acid.

Factor 2: Strength of the Acid

The second factor to consider is the inherent strength of the acid. A stronger acid will have a larger \(K_{\mathrm{a}}\) value, signifying that it produces more ions when it dissociates in solution. The strength of the acid depends on its molecular structure, particularly the stability of the ion formed when the acid molecule loses a proton (H+). The more stable the ion, the stronger the acid and the larger the \(K_{\mathrm{a}}\) value.

Factor 3: Type of Solvent

The third factor is the type of solvent in which the acid is dissolved. \(K_{\mathrm{a}}\) values are typically measured in water, but if another solvent is used, the \(K_{\mathrm{a}}\) value and so the degree of dissociation of the weak acid could change. The dielectric constant of the solvent, which is a measure of its ability to reduce the force between charged particles, influences the \(K_{\mathrm{a}}\) value of the weak acid in solution.