soap

Theory

• animal fats and vegetable oils are esters made of long chain carboxylic acids and the alcohol propane 1-2-3 triol (glycerol)

• hydrolisis of these substances under alkaline conditions produce glycerol

• and the salt of the acid present

what does the fact that soap is a long chained carbon with an ion group at the end

The fact that soap is a long chained carbon suggests that soap has both polar and non polat [rpperties hence giving its cleaning properties

Procedure of soap

• 5 g of lard was placed in a pear shaped flask

• 4g of potassium hydroxide excess and 30 cm of ethabol was added the ethanol acts as a solvent for the lard

• anti bumping granules are added to the mixture

What is the apparatus set up for: reflux

The apparatus is set up for refulx

• ensuring the complete reaction without losing any volatile material

• the material is refluxed for 30 mins

• the flask was swirled from time to time to wash materials from the side into the mixture

• after 30 mins the heat was removed and it was allowed to coolm

distillation process

• the apparatus was rearranged for distillation and the ethanol solvent was distilled off

• 20cm cubed of the ethanol was collected

• the ethanol was removed to isolate the soap as some soap may be dissolved in the ethanol and the soap would not precipitate fully to get a maximum yield

what happened with the hot solution

The hot solution was decanted quickly into a concentrated salt solution (brine)

The soap is insoluble in the salt solution so precipiatets out the solution

Using a buchner funnel the soap was filtered through a previously weighrd filter paper

Why was the soap washed

• the soap was washed to several more times with ice cold water to remove any sodium hydroxide solution clinging to the soap this is imprtant so the soap doesnt burn the skin

• the soap was allowed to dry on a piece of filter paper reweighed and subtracted to get the avtual yield

how to test the soap for its lathering qualities

• shaking a small sample of it with water

• wash hands after to remove any potassium hydroxide

explain the cleansing of soap

• soap molecules constain a long non polar carbon chain which will dissolve oils

• the oposite end of the molecule contains a polar coo na which will dissolve salts from sweat and will also dissolve in water

• This allows soap to pick up oils amd salts and then be washed down the drain

• the ionic part of the soap molecule is water soluble whole the non polar hydrocarbon part is soluble in oil and grease

• Thereofre soap allows otherwise insoluble materials to become soluble in water

why is reflux apparatus used

To ensure the hydrolisis of the fat is as complete as possible

if the mixture was boiled in an open vess;e the ethanol would be lost from the mixture

glycerol is a by product of the reaction in which soap is made

this does not distill with ethanol after the reaction is complete and remains dissolved in the hot water when added to brine to precipitate the soap

• glycerol has a much higher boiling point than ethanol and water

• hydroxyl group means there is significant hydrogen bonding

• hydrogen bonding accounts for it remaining in the sol