Alfred Ajibola
- 13th October, 2026 @ 11:47 AM
Topics in Chemistry
Chemistry Scheme of Work, SS1 Third Term Chemical Industries: Petrochemicals, Biodegradable, Non-biodegradable Wastes and Pollutants Chemical Industries: Types, Advantages, Disadvantages and Factors affecting Chemical Industries Hydrocarbons: Fractional Distillation of Crude oil and Uses of its Fractions Hydrocarbons: Sources, Classification and Test for Saturated and Unsaturated Hydrocarbons Trioxocarbonates: Preparation, Physical and Chemical Properties, Tests and Uses of Trioxocarbonates Carbon and its Compounds: Oxides of Carbon, Carbon(IV) oxide Carbon and its Compounds: Oxides of Carbon Amorphous Allotropes of Carbon Carbon: Structure and Allotropes of Carbon Salts in Chemistry: Types, Properties, and Uses of Salts Salts in Chemistry, their Classifications, Solubility, Preparations and Colors pH Indicators, Types of Indicators and Importance of pH and pOH Relative Acidity and Alkalinity (pH Scale), and Calculations on pH Bases and Alkalis: Definitions, Classification, Physical and Chemical Properties Bases: Preparation of Bases and Alkalis, Test and Uses Physical and Chemical Properties of Acids, Preparation, Test and Uses of Acids. Acid: Definition, Basicity, and Types of Acid Families of elements in the periodic table Periodic table and Classification of ElementsAcademic Questions in Chemistry
With regards to redox reactions, which of the following statement is wrong?
A. Redox reaction are examples of chemical change
B. Reduction is the gain of electron
C. Substances that donates election during chemical reaction are termed reductants
D. Oxidizing agents are always reduced in chemical reactions
E. Oxidation occurs at the cathode in electrolysis
F. Hydrogen is a reducing agent
In chemistry, physical change is associated only with the rearrangement of molecules while the internal composition of the substance remains the same.
A. True
B. False
_____ electron(s) is a term that describes the number of electron(s) in the outermost shell of an atom.
A. Outer
B. Excess
C. Valence
D. Positive
E. Negative
F. Last
_____ is the negative electrode in electrolysis.
A. Anode
B. Anion
C. Cathode
D. Cation
E. Ion
F. Electrolyte
The above diagram shows the _____ type of bond.
A. Covalent
B. Polar covalent
C. Coordinate covalent
D. Metallic
E. Van dear walls
F. Ionic
Metals are referred to as _____ in their impure state.
A. Diluted
B. Consecrated
C. Coloured
D. Ores
E. Stained
F. Strained
Metals generally have the quality to shine, glow, sparkle, glitter, reflect light and be polished. This characteristic of metals is termed _____.
A. State
B. Ductility
C. Luster
D. Malleability
E. Hardness
F. Inflorescence
The _____ spectrometry experiment conducted on isotopic elements gave a confirmation for the existence of isotopes.
A. Mole
B. Volume
C. Weight
D. Number of moles
E. Mass
F. Amount of substance
Crude oil (petroleum) is a mixture of many hydrocarbons with different boiling points. This mixture of hydrocarbons can be separated into useful groups of hydrocarbons called "fractions" by a separation technique termed fractional distillation, based on differences in boiling point (which itself depends mainly on molecular size and chain length).
Please read on various separation techniques of mixtures here.
With regards to molecular size and chain length of Hydrocarbons, larger molecules always have stronger Van Der Waals forces and higher boiling points.
Fractional distillation is defined as a chemical and physical separation technique used to split a liquid mixture into individual components (called fractions) based on their different boiling points.
It is used primarily when the components in a mixture have boiling points that are very close to one another, typically less than 25°C to 70°C apart
Note: Hydrocarbons are organic chemical compounds made up exclusively of carbon (C) and hydrogen (H) atoms only; with the carbon atoms forming its structural backbone, and hydrogen atoms attached to them via different configurations.
Below are the step by step procedure involved in the fractional distillation of petroleum (or crude oil).
Crude oil is first heated strongly in a furnace until most of it vaporizes.
The hot vapor mixture is fed into the bottom of a tall fractionating column (tower), which is hotter at the bottom and progressively cooler toward the top.
As the vapors rise up the column, they cool down. Each fraction condenses back to liquid at the height in the column where the temperature matches its boiling point range, and is drawn off on a collecting tray at that level.
Hydrocarbons with the highest boiling points (largest molecules and longest chains) condense first and are drawn off near the bottom of the column. Hydrocarbons with the lowest boiling points (smallest molecules, shortest chains) rise to the top before condensing (or remain as gas, leaving at the very top).
Any residue that doesn't vaporize even at the highest furnace temperature is drawn off at the very bottom as bitumen or residue.
The image below show the fractionating column and fractional distillation of crude oil (into its fractions), and their respective uses.
Please read on carbon, its structure and allotropes here.
The table below shows the various fractions of petroleum (or crude oil), their approximate carbon chain length, approximate boiling point range and respective uses.
| Fraction | Approx. carbon chain length | Approx. boiling range | Main uses |
| Refinery gas (LPG) | C₁–C₄ | Below 25°C | Cooking gas, fuel |
| Gasoline (petrol) | C₅–C₁₀ | 25–75°C (up to ~200°C) | Fuel for cars (petrol engines) |
| Naphtha | C₈–C₁₂ | ~75–150°C | Petrochemical feedstock (making plastics and chemicals) |
| Kerosene (paraffin) | C₁₀–C₁₆ | ~150–240°C | Jet fuel, lamp/stove fuel |
| Diesel oil (gas oil) | C₁₄–C₂₀ | ~240–300°C | Fuel for diesel engines, heating |
| Lubricating oil | C₂₀–C₅₀ | ~300–350°C | Lubricants, waxes |
| Fuel oil | C₂₀+ | Above 350°C | Fuel for ships, power stations |
| Bitumen (residue) | >C₅₀ | Does not vaporize; residue | Road surfacing (asphalt), roofing |
Note: During external examination, the exact carbon ranges and names may vary slightly. However, the trend of increasing chain length and boiling point from top to bottom of the column remains the key concept.
The trend below will help us understand various fractions of crude oil (from top to bottom) within the fractionating column.
Boiling point increases.
Molecular size (chain length) increases.
Viscosity (thickness) increases.
Volatility (ease of evaporation) decreases.
Flammability (ease of ignition) decreases.
Color becomes darker.
Please read on amorphous allotropes of carbon here.
Refinery gas / LPG (Liquefied Petroleum Gas): They are used as domestic cooking gas, and industrial heating fuel.
Petrol (Gasoline): They are used as fuel for cars, light vehicles (spark-ignition engines) and light generators.
Naphtha: It serves as a primary feedstock for the petrochemical industry, accounting for roughly 50% to 60% of global petrochemical feedstock demand. It is used to manufactire plastics (polymers), synthetic rubber, detergents, and other organic chemicals via processes like cracking.
Kerosene: It serves as fuel for jet aircraft (aviation fuel), domestic lighting and cooking (in some regions) through stoves.
Diesel oil: It serves as fuel for diesel engines (trucks, buses, generators and some cars). It is also used for heating.
Lubricating oil: It is used to lubricate machinery and engine parts in order to reduce friction and wear. It can also be processed into greases and waxes (e.g. candle wax and polish).
Fuel oil: It is used as fuel for ships (marine fuel), industrial furnaces, and power stations.
Bitumen (asphalt): It is used for surfacing and paving roads. It is also used as roofing and waterproofing materials.
Please read on bases and alkalis, their preparation, test and uses here.
Cracking is defined as the thermal or catalytic chemical process of breaking large and heavy hydrocarbon molecules into smaller, more valuable short-chain molecules (such as lighter alkanes and alkenes) by splitting the carbon–carbon bonds.
The cracking of petroleum can be achieved through the use of high temperatures and pressures (thermal cracking) or through the use of catalyst such as zeolites or silica-alumina (catalytic cracking).
The cracking of petroleum results to an added economic value of petroleum (as a result of its fractions) since there is more demand for smaller hydrocarbons (like petrol) than larger, less useful fractions (e.g heavy oils) and even the crude oil itself. As a result, the larger fractions are broken down into smaller, more useful molecules by cracking (thermal or catalytic breaking of long-chain hydrocarbons into shorter alkanes and alkenes).
The equation below show the cracking process:
This process of cracking increases the yield of valuable products like petrol, and also produces alkenes (e.g. ethene), which are essential starting materials for the plastics/polymer industry.
Below are the general economic importance of petroleum (and its fractions):
They serve as a major source of energy (fuel) for transportation, industrial and domestic use worldwide.
They serve as a crucial raw material for the petrochemical industry, providing feedstock for plastics, synthetic fibers, detergents, solvents, fertilizers, and pharmaceuticals.
They serve as a major source of national revenue for oil-producing countries through export. For.example, they are the major source of national revenue in Nigerian and Saudi Arabia.
Petroleum provides employment in exploration, drilling, refining, transportation, and marketing of its fractions.
It supports petroleum industries: shipping, road construction (via bitumen) and power generation.
They may influence inflation since fuel costs significantly affect the movement of goods and manufacturing. As a result, an increase in global oil prices may translate into general inflation in consumer prices worldwide.
Over-reliance on crude exports exposes the economy to global price volatility, exchange-rate pressures, and fiscal instability when international oil prices fluctuate.
Please read on the next topic (Chemical industries, ethical, legal and social issues) here
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Amazing facts in Chemistry
Plastic and Glass can decompose, but not in our lifetimes. It takes an average time of 450 years for plastics to decompose. As for the decomposition of glasses, it takes about 4,000 years
The only letters that failed to appear on the periodic table are letters:
Gold and copper are the only two non-silvery colored metals.
Copper is the only metal that is naturally antibacterial. For this reason, some children utilize 'copper water bottles' in schools
Water freezes faster when it’s warm than when it’s cold
Most element in their pure state exists physically in different forms. For instance, pure carbon can exist as both diamond and graphite. This phenomenon is called allotropy
If you pour a handful of salt into a full glass of water, the water level will go down rather than overflowing the glass.
Similarly, if you mix half liter of water and half litre of alcohol, the total volume of the liquid will be les than one litre
Notable points in Chemistry
Below are the physical properties of metals:
They exist in solid state.
The have high densities.
They are good conductors of heat and electricity.
The have the ability to be polished, to glow, sparkle and reflect light.
They can be bent, flattened and made into sheets called foils.
They can be drawn into wires.
Iron undergoes magnetism while most metals are poorly magnetized.
They typical have high melting point.
They generally have high boiling point.
With the exception of lithium, sodium and potassium, most metals are generally hard.
They have the ability to make sound when in contact with other objects or metals.
Please read details on the physical properties of metals here
John Dalton is an English chemist who brought clarity into the composition of matter and the basis for their chemical reactions.
Below are Dalton's Atomic Theory:
All matter consists of tiny indivisible particles called atoms.
Atoms of the same element are identical to each other in every aspect because they have the same shape and mass, while atoms of different elements are different in all respect.
Atoms are indestructible and can neither be created nor destroyed.
Atoms of different elements can combine with each other in simple whole number ratios to form compounds.
Atoms of the same element share similar physical and chemical properties. They can also combine in more than one ratio to form two or more compounds.
Meanwhile, understand that the above theories of John Dalton had been modified.
Please read on Dalton's atomic theory and its modifications here
The periodic table, also called periodic table of elements or Mendeleev's table, is a table that shows an organized arrangement of the 118 chemical elements according to their atomic number.
Out of the 118 elements; elements 1 - 94 are present in nature while elements 95 - 118 are synthesized artificially.
The manner at which elements are arranged on this table reveals some similarities in their electronic configurations and chemical properties.
A compound composed of iron (Fe) and oxygen (O) was analyzed and found to contain 69.94% iron and 30.06% oxygen. Find the empirical formula of the compound. (Molar mass of Fe=55.85, O=16)
Step 1: Identify the given parameter from the question.
Fe = 69.94%, O = 30.06%.
Empirical formula = Fe?O?
Step 2: Convert the percentages to gram. (just attribute grams to the %).
Step 3: To get the mole ratio of each element, convert the gram to moles using the formula (mole = mass/molarmass). Please merorize this formula because we always work with moles in emperical formula.
Mole of Fe: 69.94/55.85 = 1.252mol
Mole of O: 30.06/16 = 1.879mol
Step 4: Divide both sides by the smallest mole ratio.
Iron has the smallest mole ratio in our case, therefore: 1.252/1.252 = 1, 1.879/1.252 = 1.5
We now have the formula = Fe1O1.5
Step 5: Multiply each of the moles by the smallest whole number that will convert each into a whole number. (In our case, the number '2' is the smallest whole number that will make '1.5' and '1' whole numbers when multiplied by it.
For iron (Fe), we will have 1 x 2 = 2
For oxygen (O), we will have 1.5 x 2 = 3
Step 6: Write the empirical formula.
The empirical formula= Fe2O3
Iron(III)tetraoxosulphate(VI)
In chemistry, hydrocarbons can be classified as either aliphatic or aromatic. Recently, both classifications of hydrocarbon were based on their structure rather than their origin.
Aliphatic hydrocarbons are put into three main groups according to the types of bonds they possess. These are:
Alkanes
Alkenes
Alkynes
They are shown in the image below:
It's important to note the followings:
Alkanes have single bonds (only) in their structures.
Alkenes always have a carbon-carbon double bond present in their structure.
Alkynes always have a carbon-carbon triple bond present in their structure.
Aromatic hydrocarbons are classified into:
