Question

Indicate in which solvent the electrostatic force between oppositely charged ions would be the strongest, given the same separation distance, r, for the ions. The dielectric constants of the solvents are: water (80.4), methyl alcohol (32.6), ethyl alcohol (24.3), and acetone (6.5)

please explain how to get the answer!!

Answer 1

Dielectric constant is a measure of the ability of a liquid to keep charged species separate. Higher the dielectric constant of a liquid, higher is its ability to keep the charges of a solute separate. In other words, dielectric constant is the ability of the solvent to insulate the charges from each other. Higher is the insulation, the electrostatic force between the oppositely charged ions of the solute will be lesser. So, higher is the dielectric constant of the solvent, lesser is the electrostatic force between the ions of the solute in the solution. On the corollary then, lower is the dielectric constant of the solvent, more is the electrostatic force between the ions of the solute in the solution.

For the given solvents, acetone has the lowest dielectric constant value and hence the electrostatic force between ions of a solute in acetone will be the highest. The implication is that the ions will come closer and may form a neutral salt, i.e., compounds which are ionic in nature do not dissociate in low dielectric constant solvents like acetone.