Question

1. Establish the differences between concentration and activity.

2. Discuss the advantages and limitations of using an ISE for quantitative applications.

Answer 1

1.Concentration - It is the defined as the amount of a chemical species dissolved in the total volume of the mixture.

Also, the chemical potential of the ideal solution would depend on the concentration.

Acitivity - It is defined as the effective concentration of a chemical species in the solution.

The Chemical potential of the species in a real solution depends on the activity.

2.Advantages of ISE

• ISE are simple and inexpensive with wide range of applications and wide range of concentration ranges.
• It is useful in applications where only an order of the magnitude concentration is required.
• It is an invaluable method for continuous monitoring of changes in concentration.
• It is one of the very few techniques used for the measurement of both the positive and the negative ions.
• It is unaffected by the color and turbidity.

Limitations of ISE

• The  problem of ion interference and the ion selectivity is often experienced in the use of this method.
• The problem due to the other ions present in the solution than the one measured causing the ionic strength of the samples be significantly higher than that of standards leading to incompatibilty between the calibration line and the measured samples resulting in the errors in the interpolated results.