Question

Part I
So in chemistry lab, we made soap. At some point we had to vacuum filter DI water out of the soap until it was pretty much dry. Why is it necessary to filter out all the DI water? Or if it's not necessary, then why is that?

Part II
Illustrate (draw) how soap interacts with grease and water. Identify each part of the soap molecule and describe why soap can remove grease from your hands.

Part III
Fe³⁺, Ca²⁺, and Mg²⁺ ions are present in hard water. Given this fact, can you propose an explanation for "soap scum" deposits that are common in sinks and bathtubs with hard water?

Answer 1

Part I: They hae a polar end which is hydrophilic (water loving) and a long nonpolar chain which is hydrophobic (watr hating).  As a consequence they can form emulsions by suspending oil in water when their nonpolar end is in the oil and their polar end is in the water.  The emulsification of kerosene in water by means of soap is just such a process

Part II:

Part III:

Hard water is water containing high amounts of mineral ions. The most common ions found in hard water are the metal cations calcium (Ca2+) and magnesium (Mg2+), though iron, aluminum, and manganese may also be found in certain areas.

Soap scum is an informal term for the white solid that results from the addition of soap to hard water. Hard water contains calcium or magnesium ions, which react with the fatty acid component of soap.