re: HSC Chemistry Marathon Archive
Explain how the differences in the structure and composition of soaps and detergents determine their uses and their impacts on the environment. 7 Marks
There's so much things I could say but the hard part is structuring my answer to relate to the question, anyways, let's do this.
(If there's anything I should add please tell me)
Soaps and detergents both act as surfactants - they reduce surface tension of the water to improve its wetting ability. They also both act as emulsifiers - they have a polar head which is hydrophilic (able to dissolve into water forming hydrogen bonds) and a non polar hydrocarbon chain which is hydrophobic (does not dissolve in water, but dissolves in grease). This allows the grease to stay suspended as an emulsion in water. Soap is made from fatty acids in animal and vegetable oils while detergents are made from hydrocarbon chains from petroleum.
They both have similar structures however detergents may be anionic, cationic or non ionic. Most soaps are composed of sodium hence why most soaps are sodium stearate, detergents are usually hydrocarbons with a sulfate, sulfonate or other hydrophilic group on the end.
Soaps manufactured in saponification, or precipitation with sodium chloride. Alkanol from petroleum is reacted with H2SO4 to form sulfonic acid at the polar end of detergents, this then reacts with NaOH to form sodium sulfonate.
Soap has very little environmental impact because it is very easily broken down into carbon dioxide and water due to the action of bacteria.
There are two types of anionic detergents: detergents with branched chains and detergents with unbranched (linear) chains. Branched chain anionic detergents were the first detergents formed. They were not biodegradable and led to considerable environmental problems such as a build up of detergents in waterways, blocking sunlight for plants and affecting photosynthesis. Linear detergents were then created; these are much more biodegradable than the branched detergents and solved the foam problem.
If i add an acid would the equilibrium shift to the the right or left abit confused because carbonic acid is acidic so shouldnt the equilibrium shift to the the right ?
