Chapter 21.2, Problem 8RQ

Interpretation Introduction

Interpretation:

The reason for grease to be dissolved in soap water but not in the simple water needs to be explained.

Concept introduction:

Soap dissolved in water reacted with greases and formation of micelle. Soap in the form of micelle cleans the greases which collected at the center of the micelle. This property of soap makes it an emulsifier and helps to dissolve the greases.

Answer to Problem 8RQ

The grease suspended in micelles formed in the soap water. It can easily dissolve and rinsed away. This is known as the cleaning action of soap. This action is not present in the simple water, so grease is not dissolved in the simple water.

Explanation of Solution

A molecule of soap has different polarities. It reduced the surface tension of the water. At one end of soap is attached with a long hydrocarbon chain that is non-polar and hydrophobic. This hydrophobic chain is insoluble in water but soluble in oil. At the other end a polar carboxylate ion is attached. This carboxylate ion is hydrophilic means that is soluble in water but insoluble in oil and grease.

When soap is dissolved in water with it shows the property of colloidal.

The cleaning action of soap is due to micelle formation and emulsion formation, the greases are dissolved the soap water.

Conclusion

Due to the micelle formation, the greases are dissolved in soap water, and cannot dissolve in simple water.