Thermodynamics Background

Question 1

Electrostatic force depends on what parameters?

Answer 1

Charges on the individual ions and the distance between them.

Question 2

In electrolytic solutions containing many ions, does the average distance between the ions increase or decrease exponentially with their increasing concentration?

Answer 2

Decrease

Question 3

In natural waters, an ions concentration almost always overestimates its activity versus conditions at infinite dilution. What analogy describes the relationship between ion activity and ion concentration?

Answer 3

Considering a classroom of students, the number of students is the concentration and the number of students that are awake is the activity.

Question 4

What is the general equation for the activity coefficient?

Answer 4

gamma(i) = activity(i) / concentration(i)

Question 5

What are molar units (molarity, M)?

Answer 5

moles of solute per kilogram solution.

Question 6

What is the ionic strength and when is it used?

Answer 6

A general measure of the effective total ion concentration of the bulk solution. It is used for dilute electrolyte solutions.

Question 7

What is the ionic strength of seawater?

Answer 7

~ 0.7

Question 8

When is the mean salt method used?

Answer 8

When you need to estimate single-ion activity coefficients at higher ionic strength, greater than 0.1M ionic strengths.

Question 9

What complications do the Mean Salt Method and “free” ion activity coefficient account for when calculating activity coefficients?

Answer 9

ion pairing, and complex ion and dipole interactions.