Alfred Ajibola
- 22nd September, 2026 @ 05:12 PM
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
A base is defined as a substance that produces hydroxide ions (OH-) as the only negative ion when dissolved in water. Bases that are soluble in water are termed alkalis.
A base can be prepared in a variety of ways. These include the following:
1. Direct combination of a metal with oxygen, followed by reaction with water. This method applies to reactive metals, e.g sodium and potassium. The equations below shows this reaction.
Na2O(s) + H2O(l) → 2NaOH(aq)
K2O(s) + H2O(l) → 2NaOH(aq)
2. Reaction of a reactive metal directly with water. Reactive metals like Na, K and Ca reacts directly with water to form soluble bases (alkalis). Hydrogen gas is liberated in this reaction. This is shown via the equations below:
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
Ca(s) + 2H2O(l) -> Ca(OH)2 + H2(g)
3. Reaction of a metal oxide with water (for soluble oxides) gives the corresponding alkali. The equation below shows the slaking of quicklime (to slaked lime)
4. Reaction of a soluble metal salt solution with a soluble alkali. This reaction produces an insoluble metal hydroxide precipitate, which is filtered, washed, and dried: This is the precipitation method (for the production of insoluble bases). It is shown via the equations below:
CuSO4(aq) + 2NaOH(aq) -> Cu(OH)2(s) + Na2SO4(aq)
FeCl2(aq) + 2NaOH(aq) → Fe(OH)2(s) + 2NaCl(aq)
5. By electrolysis. The alkali NaOH can be prepared industrially by the electrolysis of brine (concentrated NaCl solution) in the chlor-alkali process, producing NaOH, chlorine gas, and hydrogen gas as products.
6. By heating an ammonium salt with a base (e.g. slaked lime) in the laboratory. The reaction of an ammonium salt and slaked lime or Ca(OH)2 will result in the formation ammonia, a gaseous base (alongside salt and water). This is shown via the equation below:
Note: Industrially, ammonia (a base) is prepared via the Haber process (that is, the combination of nitrogen and hydrogen gases under high pressure and temperature in the presence of iron as catalyst). This is shown via the equation below:
Please read the introduction to acids, basicity of acids and types of acids here.
1. Litmus paper test
Test: Dip red litmus paper into the substance or solution.
Observation: The red litmus paper turns blue in the presence of a base/alkali.
2. Universal indicator / pH test
Test: Add universal indicator (solution or paper) to the sample of the base or alkaline solution.
Observation: The color change corresponds to a pH greater than 7 (which is typically blue/purple for strong alkalis on the standard color chart), with pH 14 being the strongest.
3. Reaction with ammonium salts (heat test)
Test: Warm the suspected alkali with a solid ammonium salt, e.g. ammonium chloride (NH4Cl).
Observation: A gas with a sharp, pungent, and suffocating odor (ammonia, NH3) is released, which turns moist red litmus paper blue, and produces dense white fumes when a glass rod dipped in concentrated HCl is held near the gas.
Below is a chemical reaction between ammonium chloride (a soluble base) and Ca(OH)2 (slaked lime).
Note: The above test is specific for alkalis (soluble bases).
You can read on families of elements in the periodic table here.
4. Other indicators (color summary)
The color change of various indicators when added to a base or alkaline sample is summarized via the table below:
| Indicator | Color in Base/Alkali |
| Red litmus | Turns blue |
| Blue litmus | Stays blue (no change) |
| Methyl orange | Yellow |
| Phenolphthalein | Pink/magenta |
| Universal indicator | Blue to purple (pH > 7) |
The table below shows a comparison summary between an acid and a base/alkali.
| Property | Acid | Base/Alkali |
| Litmus test | Blue to Red | Red to Blue |
| pH | Less than 7 | Greater than 7 |
| Ion produced in water | H+ (H3O+) | OH- |
| Taste (Don't taste directly in the lab) | Sour | Bitter |
| Feel (Do not touch in the lab) | Watery and sour | Soapy/slippery |
| Neutralization reaction to form salt and water only | Acid + Base | Base + Acid |
You can read on the physical and chemical properties of acids, test and uses of acids here.
1. Sodium hydroxide (NaOH / caustic soda)
It is used in the manufacture of soap and detergents through saponification of fats/oils.
It is used in the production of paper and pulp (processing wood fibers).
It is the primary chemical used in in the mercerization of cotton (in the textile industry).
It is used in the manufacture of rayon and other chemicals.
It is used as a strong drain/oven cleaner.
It is used in neutralizing acidic industrial waste before disposal.
2. Calcium hydroxide (Ca(OH)2 / slaked lime
It is used in agriculture to neutralize acidic soils (liming).
It is used to make mortar and plaster (used in building and construction industry); and lime water.
It is used in water treatment (softening water and adjusting pH).
It is used to test for carbon(IV)oxide (CO2) gas (lime water test). CO2 gas turns lime water milky
It is used for the manufacture of bleaching powder.
3. Ammonia gas (NH3) / ammonium hydroxide
Manufacture of nitrogenous fertilizers (e.g. ammonium sulfate, ammonium nitrate, urea).
Manufacture of nitric acid (via the Ostwald process).
It is used as a household cleaning agent (for glass and other surfaces).
It is used as a refrigerant gas in industrial refrigeration systems.
It is used in the manufacture of explosives and synthetic fibers (e.g. nylon).
You can read on the concept of elements in chemistry here.
4. Magnesium hydroxide - Mg(OH)2
In medicine, it is used as an antacid (called 'milk of magnesia') to relieve constipation, indigestion and neutralize excess stomach acid (HCl)
It is used as a laxative.
5. Potassium hydroxide (KOH)
Manufacture of soft soaps and liquid soaps.
It is used as an electrolyte in some types of batteries (alkaline batteries).
It is used in the manufacture of potash-based fertilizers.
You can read on salts in chemistry here.
6. Other miscellaneous uses
This will include:
In titrations and analytical chemistry to determine acid concentrations.
It is used to neutralize acidic industrial effluents before safe disposal, thus consequently reducing pollution.
It is used in water and sewage treatment processes.
Bile is a weak base (produced by the liver). It aids fat digestion and neutralizes excess acid in food.
The human blood is maintained at a slightly alkaline pH (~7.4) for normal body physiology through natural buffer systems.
Although limestone/chalk (CaCO3) is a salt, they can react as mild bases with acids; found naturally in rocks and soils.
You can attempt various questions and answers in chemistry here.
Soils in some regions are naturally alkaline due to the presence of calcium and magnesium carbonates. Crops like lavender, lilac, and asparagus prefers alkaline conditions for optimum growth.
Toothpaste often contains mild alkaline substances to neutralize acids in the mouth (which cause tooth decay).
Baking soda, that is, sodium hydrogentrioxocarbonate(IV) (or NaHCO3) is mildly alkaline. It is used in baking, and as an antacid.
Household ammonia solution can act as a bleach, and is used as cleaning agents.
Caustic soda (NaOH) is a common and active ingredient found in many commercial chemical drain cleaners.
Slaked lime 'CaOH2' is used in agriculture to treat acidic soils. It is also used in the construction of buildings (as mortar, plaster, whitewash).
Note: In humans, ammonia is a base produced as a waste product of protein metabolism (converted to urea for excretion).
During decomposition or natural decay of organic (nitrogenous) matter., ammonia gas (NH3) is released into soil and atmosphere. They can be further converted to nitrites and nitrates, which are useful to plants.
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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:
