Question

The energy of an electrostatic interaction between two charged atoms is dependent on the charges on the atoms, the distance between them, and the dielectric constant of the solvent. For example, the strength of a weak acid (Ka, acid dissociation constant) depends on the strength of the electrostatic interaction between a negatively charged carboxylic acid group and a proton. The solvent dielectric constant has a large influence on the pKa for weak acids. Select the statements that correctly explain the influence of two solvents, water and hexane, on the pKa of acetic acid.
1. In water, the association of CH3COO– and H will be favored because charge-charge interactions are stronger in water.
2. Nonpolar solvents like hexane will weaken charge-charge interactions resulting in more dissociation of H .
3. The pKa will be higher in hexane.
4. Hexane cannot affect the pKa of acetic acid since hexane cannot donate or accept H .
5. More H will dissociate in water because the dielectric con

Answer 1

Answer: More H will dissociate in water due to high dielectric constant of water

Hexane cannot affect the pKa of acetic acid since hexane cannot donate or accept H .

Explanation:

The dissociation of solute ions in a solvent depends on the ability of the solvent to stabilize the ions in solution by solvating them. This ability in turn depends on the dielectric constant of the solvent. Water has a high dielectric constant hence it is able to cause more dissociation in acetic acid than other solutions hence a lower PKa. PKa of a solution a!so has to do with its ability to donate or accept hydrogen ion.