Question

In the Debye-Huckel equation describing the true activity of ions in solution, name and describe 6 terms contained therein that affect the activity, and explain how they do affect it.

Answer 1

SOLUTION:

The Debye- Huckel model is the basic model of the electrolytic. To evaluate the activity coefficient, osmotic coefficient and excess Gibbs have been studied for more than a century in ionic solutions. mobility would explain the mechanism of ion motion in terms of, the ion solvent.

The model Gibbs free energies of ion hydration, ΔG_i^hyd, give the same trends as the experiments:

(1) Smaller ions have the most favorable insertion free energies.

(2) The free energies are dominated by the enthalpies.

(3) Comparing anions to cations, lithium is approximately equivalent to fluoride.

For all ions, computed ion hydration enthalpies are negative and increase with ion size, in agreement with experiments. To make a more quantitative comparison between our 2-D model and 3-D experiments, we divided the experimental enthalpies by their ion hydration numbers and divided our theoretical results by the number of water molecules in the first hydration shell. Ion–water enthalpies grow more positive with increasing ion size because the electrostatic interaction with water weakens for larger ions.

A digital potentiometer (Equiptronics EQ-602, India) was used for the potential measurements at 25±0.1 °C. Activities were calculated according to Debye-Huckel equation. Test solutions of Sm3+ were obtained by gradual dilution of 0.1 M Sm3+solution and their potential measurements were made in unbuffered solution.