2. a) Give definition of soap and some examples of soap.
Soap is a salt that is formed from the reaction between an alkali and a fatty acid,
RCOOH.
* Soap is a sodium salt if the alkali used is sodium hydroxide.
* Soap is a potassium salt if the alkali used is potassium hydroxide.
1) General formula of soup is RCOONa or RCOOK .
2) Example of soup :
Sodium palmitate , 𝐶𝐻3 (𝐶𝐻2 )14 𝐶𝑂𝑂𝐻−
𝑁𝑎+
Sodium palmitate is a sodium salt of palmitic acid that is derived from palm oil.
Sodium stearate , 𝐶𝐻3 (𝐶𝐻2 )16 𝐶𝑂𝑂𝐻−
𝑁𝑎+
Sodium laurate , 𝐶𝐻3 (𝐶𝐻2 )10 𝐶𝑂𝑂𝐻−
𝑁𝑎+
b) Briefly explain the history of soup manufacturing in a flowchart.
2200 B.C.
Although it is believed by many that soap's history actually began around 2800 B.C. in
Babylonia (where historians found a barrel containing a soap-like substance) unarguable
proof of soaps existence was first provided by a 2200 B.C. Mesopotamian clay tablet with an
actual soap recipe inscribed on it. This ancient soap making technique described mixing
potash and oils to form a cleaning agent.
1500 B.C.
Egyptian manuscripts describe a matter created by combining animal fats and vegetable oils
to create a soap-like substance. The ancient documents go on to explain another type of soap
that is used in the production of wool.
200 A.D.
The very first allusion to soap making in literature occurred by a famous Greek physician
named Galen.
3. 600 A.D.
Soap making guilds were formed and the modern formula for soap that we use today was
created.
Currently
Soap is being produced in the same way as it was centuries ago after the industrial revolution.
As almost all people in this modern age purchase and use commercially manufactured soaps,
the history of soap making is at somewhat of a standstill.
c) Soap can be prepared through saponification. Use a flow chart to show soap preparation
process in the laboratory, starting with the raw materials. Include any relevant chemical
process.
Saponification process is a hydrolysis process of ester ( oil or fat ) by alkali.
Manufacturing of soap can be divided into 2 stage
Stage 1
I. The two parts of the oil or fat molecule are separated by heating the oil with alkaline
solution through hydrolysis process.
II. In this process, the ester molecule is broken up into fatty acid and glycerol by water
in the presence of alkali which act as catalysts.
900 A.D.
Soap started to be produced commercially and sold for .3 Dinars per bar.
1700-1800 A.D.
During the industrial revolution, soap began its production in factories and stopped being
produced in the home kitchen.
4. Stage 2
I. Fatty acid that is released in stage 1 reacts with alkali to form sodium salt of fatty
acid which is soap
Fatty acid + sodium hydroxide ( alkali ) Sodium salt of fatty acid (soap) + water
Example:
Vegetable oil + sodium hydroxide sodium salt of fatty acid + glycerol
Preparing soap in laboratory
Aim : To prepare soap through the saponification process.
Material : Palm oil , 5 mol dm−3
concentrated sodium hydroxide solution , sodium chloride
powder , red litmus paper and distilled water.
Apparatus : 250 cm3
beaker , glass rod , tripod stand , wire gauze , Bunsen burner , spatula ,
10 cm3
and 100 cm3
measuring cylinder , filter funnel , filter paper and test tube
Ester + Water fatty acid+ glycerol
Hydrolysis
Alkali actas catalysts
( ester) ( alkali ) ( soap)
5. Procedure :
1. Approximately 5 cm3
of palm oil is poured into the beaker.
2. Approximately 30 cm3
of concentrated sodium hydroxide solution is added into
the same beaker.
3. The mixture is then boiled slowly while being stirred with a glass rod for 10
minutes. The mixture is prevented from bubbling.
4. 50 cm3
of distilled water and two spatulas of sodium chloride are added.
5. The mixture is boiled and stirred for s few minutes.
6. The mixture in the beaker is left to cool down and the resulting white solid is
filtered.
7. The white solid that is produced is washed with a little distilled water and dried
with filter paper.
8. The following test are carried out on the white solid :
a) Touched with fingers
b) Some of the white solid is shaken together with some water in a test tube
c) Tested with red litmus paper
9. The observation are recorded in the table provided.
Observation :
Test on the white solid Observation
Touch with fingers Smooth
Shake with water Many bubble is produced
Red litmus paper Change to blue
Analysis :
The white solid produced is an alkaline soap.
Table salt is added to lower the solubility of soap in water so that the soap can
precipitated out.
When sodium hydroxide solution is added , the process of saponification occurs to
produce sodium salt fatty acid which is soap.
Conclusion :
Soap can be prepared through the saponification process.
6. d) Give definition of detergent and some examples of detergent.
Detergent is a salt that is produced from the reaction between an alkali and a
sulphonic acid.
A detergent is the sodium salt of sulphonic acid.
Example of detergent:
a) Sodium alkyl sulphate
Synthetic detergent are made from hydrocarbons that are obtained as by-products
of the petroleum industry, for example propene gas, 𝐶3 𝐻6
Detergent may contain many other substances in addition to the substances that
does cleaning and make it more effective which is called addictives.
e) Use a flow chart to summarize the steps in preparation of detergent.Include any
relevant chemical equation.
A synthetic detergent, a sodium alkyl sulfate called sodium dodecylsulfate, will be
prepared by reacting dodecyl alcohol (dodecanol) with sulfuric acid.
Dodecanol + Sulfuric acid Dodecylsulfate
The resulting dodecylsulfate is converted to the sodium salt by a reaction with
sodium hydroxide.
Dodecylsulfate + Sodium Hydroxide Sodium dodecylsulfate
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7. f) Both soap and detergent so much better than water alone. Use a flow chart and colourful
diagram to summarize the cleansing action of soap and detergent.
When added into water, soap molecule will dissociate into sodium or potassium ions
and soap ions.
Soap ions can be divided into two part :
tail
Soap molecule can reduce the surface tension of water to allow it to wet a material’s
surface better.
Cleansing action of soap
I. The soap molecule dissolves in water and reduces the surface tension of
water. Water wets the dirty surface.
II. The hydrophilic region dissolve in water.
III. The hydrophobic region dissolve in dirt.
head
Consists of the anion region
Is ionic
Called the hydrophilic region
Dissolve in water
Consists of the hydrocarbon
region
Molecule that has covalent
characteristics
Called the hydrophobic region
Dissolve in grease or oil (dirt )
8. IV. The dirt is lifted off the surface of the material upon shaken and
suspended in water.
V. The tail region emulsifies and breaks up the grease into small drops.
VI. When shaken, the water molecules will attract the soap ions and cause
the dirt to detach from the surface of the material.
VII. The soap bubbles help to float the dirt emulsion in the water. When
rinsed, the dirt will be removed together with water.
The cleansing action of detergent and soap is fundamentally same.
When a detergent dissolves in water, its molecule will dissociate to form sodium or
potassium ion and detergent ion ( detergent anion ).
The detergent ion such as R-O- SO3
−
can be represented in a simplified form by
structure below.
Cleansing action of detergents
I. Detergent molecule dissociate to form sodium or potassium ions and detergent ions.
II. Hydrophilic region dissolve in water. Hydrophobic dissolve in grease and emulsifies
the grease.
III. When the water is shaken, the detergent ion will remove the dirt.
O- SO3
−
Ionic head
Hydrophilic head
Dissolve in water
Hydrocarbon tail
Hydrophobic head
Dissolve in grease(dirt)
9. g) Compare and contrast the effectiveness of cleansing action of soap and detergent in hard
water by using mid map or table.
Hard water contains a great amount of calcium and magnesium ions.
Soap cannot be used in hard water because the magnesium and calcium ions wil
react with soap ions to form a non-soluble precipitate in water that is called a soap
film or scum. Soap cannot produce bubble in hard water.
Soap scum is not easily cleaned. It will leave a clear sediment that can be seen on
the clothes and cause the clothes to feel hard.
Properties Soap Detergent
Cleaning power Less powerfull More powerfull
Ease of rinsing It is difficult to wash away all soap
on clothes. The soap that remains
leave and odour and spoils the
fabrics
Rinse out well from clothes
pH Slightly alkaline Can be controlled to suit the
cleaning task
Molecular structure Determined by the fatty acids found
in the oil or fat used to produce
soap
Can be modified to suit the
cleaning task. For example, a
detergent can be made
specially for cleaning toilet
bowls
Formation of scum Form scum with hard water Does not form scum with
hard water
10. h) Detergent consists of various addictives. What is the purpose of adding detergent
addictives ? Construct a mind map to show the addictives in detergents and its functions.
Addictives Example Function
Biological enzyme Amylases, proteases,
cellulases
To remove protein
stains such as blood
Whitening agent Sodium perborate To convert stains into
colourless substances
Optical whitener Fluorescent dyes To add brightness and
whiteness to white
fabrics
Builder Sodium tripolyphosphate To enhance the cleaning
efficiency of detergent
by softening the water
Suspension agent carboxymethylcellulose To prevent the dirt
particles removed from
redepositing onto
cleaned fabrics.
Filler Sodium sulphate, sodium
silicate
To add to tha bulk of
the detergents and
enable it to be poured
easily
Foam control agents Silicones To control foaming in
detergent
Fragrance - To add fragrance to
both detergent and
fabrics
