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.

In water, the association of CH3COO– and H will be favored because charge-charge interactions are stronger in water.

Nonpolar solvents like hexane will weaken charge-charge interactions resulting in more dissociation of H .

The pKa will be higher in hexane.

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

More H will dissociate in water because the dielectric constant is higher.

Answer 1

The pKa will be higher in hexane.

More H will dissociate in water because the dielectric constant is higher.

Step-by-step explanation:

In water, the ionisation of ionic compound increases because of higher value of dielectric constant of water. Higher value of dielectric constant of medium between two charges reduces the force between two charges. That is why ionisation of CH₃COOH will be higher in water.

In hexane the ionisation will be low so
`K_a` will be low , hence

`pK_a` will be high.