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Lab Report(Soap Preparation)
Abstract
Soaps are generally prepared by saponification, this is the alkaline hydrolysis of oils and natural fats.
Soaps are however not effective in hard water and instead a detergent is advised. The detergents
are prepared using organic Phosphate and Sulfonate acids. The saponification process also provides
a commercial source of glycerol which is given off from the trygliceride fatty acids that make up the
oils used in the process. The aim of this experiment was to prepare soaps using an alkaline solution
of Sodium Hydroxide and a fat and to compare its properties with other detergents.
Materials and reagents
Vegetable oil, 6M NaOH solution, 20g NaCl, 125ml Erlenmeyer flask, 95% Ethanol, 100ml beaker,
Filter paper and a filtration apparatus.
Procedure
1. Put 2.0ml of the vegetable oil and 3.0ml 6M Sodium Hydroxide solution into the 100ml
beaker.
2. Cover the contents of the beaker and carefully bring the mixture to boil on a Bunsen Burner.
3. Heat the contents until most of the water has evaporated and a thick content is visible. The
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heating should take approximately five minutes.
4. After heating, turn off the heat source and allow the contents to cool off for 15 minutes
before removing the watch glass cover.
5. As the contents cool, prepare a concentrated Sodium Chloride solution by dissolving the 20g
into 60ml distilled water.
6. After the heated mixture cools, add 20ml of the Sodium Chloride solution made in step five
into the beaker. Use a spatula to loosen the solid in the beaker. Stir the mixture well.
Decant the liquid. Use a wire to prevent the soap falling from the beaker.
7. Add the last 20cc sodium chloride solution as you repeat step six. Stir the solution and filter
through a filter funnel lined with layers of filter paper and allow the soap to collect in the
paper.
8. Wash the collected soap to remove any traces of NaCl.
Conclusion
The soap formed from this experiment is a soapy detergent and can be in powder form or solid form.
The quantity of the soap formed depends on the amount of reagents used. This procedure is
applicable even in industrial set ups. The sodium chloride is used for the purposes of salting out and
helps in the crystallization of the soap.
Questions
1.Why do long chain fatty acids melt higher than short chain acids?
Long chain fatty acids posses more carbon atoms. The carbon atoms are bonded together thereby
resulting more bonds. Melting is as a result of breaking these bonds. The longer the carbon chains
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the higher the molecular weight of t6he fatty acids hence more energy that comes from a higher
temperature.
2.Why may you use the same weight of fat in your soap preparation regardless of the type of fatsaturated or unsaturated- employed?
The determining factor in soap preparation is the alkali used, the hydrolysis process depends on the
alkali and stops once the the alkali is depleted regardless of the available fats.
3.Why are vegetables fats (oils) liquid, while animal fats are solid?
The levels of saturation determines the molecular state of organic molecules. Fats are hydrogenated
and are thus more saturated and tend to be solid at room temperature while oils have fewer double
and are unsaturated hence liquids at room temperature.
4.Why are naturally occurring fatty acids even-chained?
This is due to their synthesis which involves Acetyl Co-enzyme A which carries a two carbon atom
group.
5.Why do waxes, Vaseline and mineral oil all feel greasy like fats, even though they are not
triglycerides?
Wax is branched chain acid and alcohol . When dehydrated, an ester forms resulting in a long chain
non polar compound.
6.What is soda ash? How does it form? Why is it useful in water softening?
This sodium carbonate which usually crystalline highly hygroscopic and soluble in water. It is formed
from roasting trona which is Sodium Hydrogen Carbonate. The CO2 is driven off and the ash
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remains.
It is used in water softening since it competes with Calcium and Magnesium ions preventing their
binding with the soap used.
7.Using the same weights of fat and alkali, would you get more or less soap by using KOH instead of
NaOH?
Depending on the basis used, using equal moles result into more Potassium soap grams. Using equal
grams will result into more Na soap since there are more moles of Na.
8.Why can you unclog a kitchen-sink drain by pouring lye down into it?
Kitchen clogs are fat therefore using Lye unclogs the sink. Lye hydrolyzes fats and breaks the fats
into soap and forms glycerol as residue.