Question

1.) Chlorofluorocarbons (CFCs) were introduced as refrigerants in the 1930s, replacing other gases that were toxic and corrosive. How do the molecular shape and polarity of CFCs contribute to the many desirable qualities they have as refrigerants? Given that they are such desirable refrigerants, why are they banned? What chemistry is involved? How has their molecular shape and polarity had harmful effects on the atmosphere?

2. Chemically, how does soap work to remove grease? Give some other related examples.

Answer 1

1.Carbon in CFCs are arranged in tetrahedral symmetry.because of large difference in atomic size between hydrogen and flurine it deviate from perfect tetrahedral symmetry. they are volatile compounds,but less than their parent alkanes. the decreased polarity attributed to the molecular polarity induced by the halides. the CFCs have high boiling point because chloride is more polarizable than fluoride. because of good polarity CFCs are good solvents and their boiling point make them suitable as refrigerant.  

Eventhough they are suitable refrigerant they are banned because they harmful to ozone in the atmosphere. the most important chemistry behind this is CFCs cause the photo induced splitting of c-cl bond.

CCl3CCl2+Cl-

the chlorine atom behaves different from ordinary chlorine molecule. it has long lived in upper atmosphere and catalyses the splitting of ozone in to o2. the depletion of ozone causes the arrival more solar radiation towards earth surface. so that the temperature on the earth increases this leads to green house effect.this is the reason for CFCs considered as a harmful substance and it is banned.

2.The working principle of cleansing action of soap is as follows. soap is made up of an emulsifier. it containes at one end hydrophilic part[water loving] and at the another end hydrophobic part[oil loving part]. the hydrophobic part attached to the grease or oil part in the cloths and the hydrophilic part attached to the water part. while we rubbing the cloths by friction the water grabs the oil loving end along with the grease its attached to, and carried off.

another examples of this types are detergent , shampoos, shaving creams etc.