Today on our JAMB Free Tutorial, we will focus on CHEMISTRY. We will treat Esters, Fats, and Oil. We will also ask 10 objective questions.
Our topics are ESTERS, FATS and Oil. You can check the table of content (content in post) below to scan through the sub-topics we will teach.
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They are organic compound which possess the functional group COOR. Their general formula is RCOOR. Ester are the main constituent of natural occurring fat and oil with pleasant smell / odour.
It is a reaction between Alkanols and Alkanoic acids to produce salt and water.
RCOOH + ROH ⟶ RCOOR + H2O
|IUPAC Name||Structural Formula||Flavour|
Esters with long carbon chain are present in vegetable oil and animal fat. Fat and oil esters or propan -1, 2, 3 – triol are long chain fatty acids such as hexadecanoic acid or palmitric acid.
Lab. Prep. Of CH3COOC2H5 (Ethyl Ethanoate)
CH3COOC2H5 is prepared by the esterification between ethanol and CH3COOH (ethanoic acid) in the presence of conc. H2SO4.
The following is carried out to purify the distillates;
- Shake the distillate in a separating funnel with conc. Na2CO3 solution to remove the acidic impurities.
- Discard the lower aqueous layer and shake the upper layer with a concentrated solution of CaCl2 to remove the C2H5
- Discard the lower layer again and containing anhydrous CaCl2 and leave it to stand for a day to remove any water present in the mixture.
- Filter the mixture, distil it over a water bath and collect the fraction which distils between 74oc to 79o The fraction contains pine of ethyl ethanoate which is almost free of ethoxy ethane.
Physical properties Of Esters
- Lower and intermediate esters are colourless, volatile liquids with pleasant smell while high molar mass esters are colourless wax-like solid.
- Low molecular mass esters are fairly soluble in water. However, the solubility of esters in water decreases with increase in molecular mass.
NB: All esters are soluble in organic solvents.
- The boiling points are much lower than those of alkanols and alkanoic acid of comparable masses. This is due to the absence of hydrogen bond in esters.
Differences between neutralization and esterification
|1||The reactions are covalent||The reaction are ionic or electrovalent.|
|2||Heat and catalyst are required.||No heat or catalyst required.|
|3||It is a reversible reaction||It is not a reversible reaction.|
|4||Main products is ester which is covalent||Main product is salt which is ionic or electrovalent.|
Test for Ester
To a small amount of the substance, dissolve the C2H5OH, add 2 to 3 drops of phenopthaline with 2 to 3 drops of NaOH solution. The solution becomes pink. However on warming, the pink colour disappears showing the presence of ester.
- Used in making artificial perfumes because it has sweet smell.
- Used in making artificial flavours and essence in cold drink, ice-cream and sweet.
- Used in preparation of many organic compound.
- They are used as solvents for oil, fat, paints and vitamins.
- They are used as softening agent for plastics and resins.
Before we proceed, let’s show your 7 fun facts about Chemistry:
Did you know
- It’s possible to die from drinking too much water.
- By the time you feel thirsty, you’ve already lost about 1% of your body’s water.
- Sometimes, hot water freezes more quickly than cold water. A high school student documented the effect, which bears his name (the Mpemba effect).
- Hot peppers get their heat from a molecule called capsaicin. While the molecule acts as an irritant to mammals, including humans, birds lack the receptor responsible for the effect and are immune to the burning sensation from exposure.
- One bucket full of water contains more atoms than there are buckets of water in the Atlantic ocean.
- Hydrogen is the most abundant element in the universe, while oxygen is the most abundant element in the Earth’s atmosphere, crust, and oceans (about 49.5%).
- Did you know that our JAMB CBT App has Chemistry tutorial for JAMB Candidates? It also has over 10,000 past questions and answers. You can get the App HERE.
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FATS AND OIL
They belongs to a group of compound known as lipids. Fats are from animals while oil are from plants. Both fat and oil are esters of trihydric alkanol (glycerol).
Fatty acids are naturally occurring monocarboxylic acids in fats and oil.
They are divided into two
- Saturated and
- Unsaturated fatty acids
Saturated Fatty Acids
Is one with a carbon chain in which all carbon-carbon bond are single bond. E.g.: palm oil and coconut oil.
Palmitric acid (palm oil) >> CH3(CH2)14COOH – hexadecanoic acid
Stearic acid >> CH3(CH2)16COOH – octadecanoic acid
Unsaturated Fatty Acids
This contains one or more double bond in their molecules. E.g.: olive oil/peanut oil and vegetable oils.
CH3(CH2)7 = CH(CH2)7COOH – octadec-9-enoic acid (oleric acid) which is gotten from olive oil.
Fats have higher melting point than oil because they are composed of higher proportion of ester of saturated fatty acids.
While oil have lower melting point than fats because they are composed of higher proportion of ester of unsaturated fatty acids.
Hydrogenation of Oils
Oil are changed into fat by hydrogenation. This process is carried out by using oil, like palm oil, groundnut oil or soya bean oil which is heated to about 100oc in the presence of finely divided Nickel catalyst at about 5atm. The hydrogen is added across the double bond of the unsaturated carbon chain in the oil.
It is the alkaline hydrolysis of fats and oil to produce soap and glycerol.
- Fats or oil + caustic soda ⟶ soap + glycerol
It is any substance that has the ability to clean an object.
Types of Detergents
These are sodium salts of fatty acids. They are saponification product of fats and oil. In the commercial manufacturing of soap, concentrated NaCl solution is added decrease the solubility of the soap, so that it separate out as a hard cake on the surface on cooling. This process is called salting out.
Each molecule of soap possesses a long hydrocarbon chain R attached to an ionic head which is either COO–Na+ or COO–K+. The hydrocarbon tail is hydrophobic (insoluble in water but soluble in oil and organic solvent) while the ionic head is hydrophilic i.e. it is soluble in water.
NB: When soap dissolves in water, the soap molecules forms spherical clusters called micelles.
Advantages and Disadvantages of Soapy Detergent
- It is a good cleansing agent in soft water.
- In hard water, it forms scum.
- In acidic water, it reacts with the excess hydrogen ion to form unionized fatty acids which lowers the cleansing effects of the soap.
- Soap is biodegradable i.e. it can be easily decomposed by bacteria into simple inorganic substances. Hence, it doesn’t cause water pollution.
Soapless Or Synthetic Detergent:
The detergent molecules has a hydrophobic tail and hydrophilic head. The hydrophobic tail is either a long chain hydrocarbon between 12 to 18 or a benzene ring with a long alkyl group attached. The hydrophilic head can be positively, negatively charged or even neutral.
NB: The high solubility of soapless detergent in water is due to the SO3–Na+ that is presence in the molecule.
Advantages And Disadvantages of Soapless Detergent
- It doesn’t form scum or react with hydrogen ion.
- It retains its cleansing properties irrespective of the type of water used.
- In aqueous solution detergent are neutral, however soap hydrolysis to give a slightly alkaline solution.
- It can also be tailor made for specific purpose as it breaks up the oil slick.
- Soapless are non-biodegradable hence they cause water pollution as they clog water ways.
THE END OF TODAY’S TUTORIAL
Credit: This BIOLOGY tutorial was prepared by Ejimgini, Ozioma Promise a Biology/Chemistry Tutor.
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- The alkanol obtained from the production of soap is?
- An organic compound with a pleasant smell is likely to be
- Reaction between ethanoic acid and pentanol will give you?
A. Ethyl propanoate
B. Propyl ethanoate
C. Ethyl pentanoate
D. Pentyl ethanoate
- Salt formers are referred to as
- The poor solubility of esters in water is due to
A. Absenceof hydrogen bonding.
B. Presence of hydrogen bonding
C. Presence of oxygen hydrogen bonding
D. Absence of oxygen hydrogen bond
- The saponification of an alkanoate to produce soap and alkanol involves
- In manufacturing of soap, sodium hydroxide is used for
A. Increase solubility
B remove impurities
C. Decrease solubility
D. Make soap more cheap.
- Esters can be reduced by
A. Oxidizing agents
B. Reducing agents
- Sodium trioxocarbonate(v) is used to remove ____in the preparation of ethyl ethanoate
A. Basic impurities
B. Acidic impurities
C. The distillates
- Laundry soap can be prepared by the use of
A. Sodium salts
B. Calcium salts
C. Carbonates salt
D. Dicarbonates salts
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