Sample WAEC-style Practice Questions (Original Content)
WAEC Style
Question 1
Which of the following elements has the electronic configuration 1s2 2s2 2p6 3s2 3p3?
A. Nitrogen
B. Phosphorus
C. Sulfur
D. Chlorine
Answer: B. Phosphorus
Explanation: The total number of electrons is 2+2+6+2+3 = 15. The element with atomic number 15 is Phosphorus.
Question 2
The isotope of Hydrogen that contains no neutrons in its nucleus is:
A. Deuterium
B. Tritium
C. Protium
D. Helium
Answer: C. Protium
Explanation: Protium (1H1) has 1 proton and 0 neutrons. Deuterium has 1, and Tritium has 2.
Question 3
Which of the following forces is responsible for the low boiling points of noble gases?
A. Covalent bonds
B. Ionic bonds
C. Van der Waals forces
D. Hydrogen bonds
Answer: C. Van der Waals forces
Explanation: Noble gases are monoatomic and are held together by very weak induced dipole-dipole attractions (Van der Waals forces).
Question 4
The geometric shape of the Carbon (IV) oxide molecule is:
A. V-shaped
B. Linear
C. Tetrahedral
D. Trigonal planar
Answer: B. Linear
Explanation: CO2 has two double bonds and no lone pairs on the carbon atom, resulting in a 180-degree bond angle.
Question 5
As we move from left to right across a period in the periodic table, the atomic radius:
A. Increases
B. Decreases
C. Remains constant
D. Increases then decreases
Answer: B. Decreases
Explanation: Increased nuclear charge pulls the electron shells closer to the nucleus, reducing the radius.
Question 6
Which of the following is most suitable for separating the components of ink?
A. Filtration
B. Distillation
C. Paper Chromatography
D. Crystallization
Answer: C. Paper Chromatography
Explanation: Chromatography separates mixtures based on the different rates at which components travel through a stationary phase.
Question 7
A sample of a substance is considered pure if it has a:
A. Variable boiling point
B. Fixed melting point
C. High density
D. Different color after heating
Answer: B. Fixed melting point
Explanation: Pure substances have sharp, constant melting and boiling points, unlike mixtures.
Question 8
The equation PV = nRT represents the:
A. Boyle's Law
B. Charles's Law
C. Ideal Gas Law
D. Dalton's Law
Answer: C. Ideal Gas Law
Explanation: This equation combines Boyle's, Charles's, and Avogadro's laws into a single relationship.
Question 9
Compare the rates of diffusion of Hydrogen (H2) and Oxygen (O2). (H=1, O=16)
A. Hydrogen diffuses 4 times faster
B. Oxygen diffuses 4 times faster
C. Hydrogen diffuses 16 times faster
D. They diffuse at the same rate
Answer: A. Hydrogen diffuses 4 times faster
Explanation: Rate is inversely proportional to the square root of the molar mass. sqrt(32/2) = sqrt(16) = 4.
Question 10
Ammonium chloride can be separated from Sodium chloride by:
A. Decantation
B. Evaporation
C. Sublimation
D. Magnetism
Answer: C. Sublimation
Explanation: Ammonium chloride changes directly from solid to gas when heated, leaving the salt behind.
Question 11
Which of the following is an example of a chemical change?
A. Dissolving sugar in water
B. Magnetizing an iron nail
C. Burning magnesium ribbon
D. Melting ice
Answer: C. Burning magnesium ribbon
Explanation: Burning magnesium creates a new substance, Magnesium oxide, through a non-reversible reaction.
Question 12
The maximum number of electrons that can occupy the 3p subshell is:
A. 2
B. 6
C. 10
D. 14
Answer: B. 6
Explanation: The p subshell always contains 3 orbitals, each holding 2 electrons, for a total of 6.
Question 13
Which of the following is a physical property of Chlorine gas?
A. It bleaches moist litmus paper
B. It reacts with metals
C. It is a greenish-yellow gas
D. It supports combustion
Answer: C. It is a greenish-yellow gas
Explanation: Color is a physical property. The other options describe chemical reactions (bleaching and reacting).
Question 14
What is the oxidation number of Nitrogen in the NH4+ ion?
A. -3
B. +3
C. -5
D. +1
Answer: A. -3
Explanation: N + 4(+1) = +1. N + 4 = 1. N = -3.
Question 15
The standard molar volume of a gas is measured at 0 degrees Celsius and ______ pressure.
A. 1.0 atm
B. 2.0 atm
C. 10.0 atm
D. 0.5 atm
Answer: A. 1.0 atm
Explanation: Standard pressure is 1 atmosphere (or 760 mmHg).
Question 16
The solubility of KNO3 in water ______ as the temperature increases.
A. Decreases
B. Remains constant
C. Increases
D. Becomes zero
Answer: C. Increases
Explanation: For most solid salts like Potassium nitrate, solubility is directly proportional to temperature.
Question 17
Which of the following is a neutral oxide?
A. Carbon (IV) oxide
B. Nitrogen (I) oxide
C. Sulfur (IV) oxide
D. Calcium oxide
Answer: B. Nitrogen (I) oxide
Explanation: N2O (laughing gas), NO, and CO are neutral oxides that do not react with acids or bases.
Question 18
A basic solution has a pH value:
A. Equal to 7
B. Less than 7
C. Greater than 7
D. Equal to 0
Answer: C. Greater than 7
Explanation: Acids are below 7, neutral is 7, and bases (alkalis) are above 7.
Question 19
The term "water of crystallization" refers to water that is:
A. Used to dissolve a salt
B. Found in the atmosphere
C. Chemically combined in the crystal structure of a salt
D. Produced during a neutralization reaction
Answer: C. Chemically combined in the crystal structure of a salt
Explanation: Example: CuSO4.5H2O, where the 5H2O is the water of crystallization.
Question 20
The process of adding Chlorine to water during treatment is to:
A. Remove dirt
B. Make the water clear
C. Kill harmful bacteria
D. Soften the water
Answer: C. Kill harmful bacteria
Explanation: Chlorination is the sterilization step in water purification.
Question 21
Which of the following is the most reactive halogen?
A. Fluorine
B. Chlorine
C. Bromine
D. Iodine
Answer: A. Fluorine
Explanation: Reactivity of halogens decreases down the group. Fluorine is the most electronegative and reactive.
Question 22
The energy required to remove the most loosely bound electron from a gaseous atom is:
A. Electron affinity
B. Electronegativity
C. Ionization energy
D. Activation energy
Answer: C. Ionization energy
Explanation: This is the formal definition of first ionization energy.
Question 23
Which of the following elements is a transition metal?
A. Calcium
B. Aluminum
C. Copper
D. Sodium
Answer: C. Copper
Explanation: Copper belongs to the d-block elements, which are the transition metals.
Question 24
During the electrolysis of Copper (II) tetraoxosulfate (VI) using copper electrodes, the mass of the anode:
A. Increases
B. Decreases
C. Remains constant
D. Doubles
Answer: B. Decreases
Explanation: The copper anode dissolves into the solution as Cu2+ ions.
Question 25
A catalyst increases the rate of reaction by:
A. Increasing the temperature
B. Increasing the collision frequency
C. Lowering the activation energy
D. Increasing the pressure
Answer: C. Lowering the activation energy
Explanation: A catalyst provides an alternative reaction pathway with a lower energy barrier.
Question 26
The functional group of the Alkanoic acid series is:
A. -OH
B. -CHO
C. -COOH
D. -CO-
Answer: C. -COOH
Explanation: This is the carboxyl group characteristic of organic acids like ethanoic acid.
Question 27
Which of the following is an unsaturated hydrocarbon?
A. CH4
B. C2H6
C. C2H4
D. C3H8
Answer: C. C2H4
Explanation: Ethene (C2H4) contains a double bond, making it unsaturated. The others are alkanes.
Question 28
The process by which large molecules are broken down into smaller ones by heat is:
A. Polymerization
B. Cracking
C. Saponification
D. Esterification
Answer: B. Cracking
Explanation: Cracking is used in petroleum refining to produce petrol from heavier fractions.
Question 29
Which gas is used in the manufacture of margarine from vegetable oils?
A. Oxygen
B. Nitrogen
C. Hydrogen
D. Chlorine
Answer: C. Hydrogen
Explanation: The process is called hydrogenation, which hardens the oil into a solid fat.
Question 30
What is the IUPAC name of the compound CH3CH(CH3)CH2CH3?
A. Pentane
B. 2-methylbutane
C. 3-methylbutane
D. Isopentane
Answer: B. 2-methylbutane
Explanation: The longest chain has 4 carbons (butane) with a methyl group on the second carbon.
Question 31
Which of the following is a synthetic polymer?
A. Starch
B. Cellulose
C. Nylon
D. Proteins
Answer: C. Nylon
Explanation: Nylon is man-made; starch, cellulose, and proteins are natural polymers.
Question 32
The reaction between an organic acid and an alcohol to produce an ester is called:
Which of the following is a use of Carbon (IV) oxide?
A. Filling weather balloons
B. As a fuel in engines
C. In fire extinguishers
D. For respiration in animals
Answer: C. In fire extinguishers
Explanation: CO2 is denser than air and does not support combustion, making it ideal for smothering fires.
Question 34
The temporary hardness of water is caused by the presence of:
A. Calcium tetraoxosulfate (VI)
B. Magnesium trioxocarbonate (IV)
C. Calcium hydrogen trioxocarbonate (IV)
D. Sodium chloride
Answer: C. Calcium hydrogen trioxocarbonate (IV)
Explanation: This salt can be removed by boiling, which is why it is called "temporary" hardness.
Question 35
The method used to extract Aluminum from Bauxite is:
A. Reduction with carbon
B. Thermal decomposition
C. Electrolysis of molten Alumina
D. Displacement by Iron
Answer: C. Electrolysis of molten Alumina
Explanation: Aluminum is too reactive to be reduced by carbon, so the Hall-Heroult electrolytic process is used.
Question 36
Which of the following gases is produced when coal burns in a limited supply of air?
A. Carbon (IV) oxide
B. Carbon (II) oxide
C. Sulfur (IV) oxide
D. Methane
Answer: B. Carbon (II) oxide
Explanation: Incomplete combustion produces CO (Carbon monoxide), which is highly poisonous.
Question 37
The percentage by mass of Carbon in Ethanol (C2H5OH) is: (C=12, H=1, O=16)
A. 52.2 percent
B. 26.1 percent
C. 13.0 percent
D. 46.0 percent
Answer: A. 52.2 percent
Explanation: Molar mass = 46. Carbon mass = 24. (24/46) * 100 = 52.17.
Question 38
Which of the following is a property of graphite?
A. It is extremely hard
B. It is used as an abrasive
C. It conducts electricity
D. It has a tetrahedral structure
Answer: C. It conducts electricity
Explanation: Graphite has delocalized electrons between its hexagonal layers.
Question 39
The catalyst used in the manufacture of Sulfuric acid by the Contact process is:
A. Finely divided Iron
B. Vanadium (V) oxide
C. Manganese (IV) oxide
D. Nickel
Answer: B. Vanadium (V) oxide
Explanation: V2O5 is used to catalyze the oxidation of SO2 to SO3.
Question 40
Hydrocarbons that undergo only substitution reactions are:
A. Alkanes
B. Alkenes
C. Alkynes
D. Alkanols
Answer: A. Alkanes
Explanation: Alkanes are saturated and lack double/triple bonds, so they cannot perform addition reactions.
Question 41
Which of the following ions is discharged first at the cathode during the electrolysis of brine?
A. Sodium ion
B. Hydrogen ion
C. Hydroxyl ion
D. Chloride ion
Answer: B. Hydrogen ion
Explanation: Hydrogen is lower in the electrochemical series than Sodium, so it is preferred for discharge.
Question 42
The major air pollutant responsible for acid rain is:
A. Carbon (II) oxide
B. Methane
C. Sulfur (IV) oxide
D. Helium
Answer: C. Sulfur (IV) oxide
Explanation: SO2 reacts with atmospheric moisture to form sulfurous and sulfuric acid.
Question 43
Which of the following is the chief ore of Tin?
A. Bauxite
B. Cassiterite
C. Galena
D. Haematite
Answer: B. Cassiterite
Explanation: Cassiterite is SnO2.
Question 44
What color change is observed when SO2 is bubbled through acidified K2Cr2O7?
A. Purple to colorless
B. Orange to green
C. Blue to red
D. Yellow to brown
Answer: B. Orange to green
Explanation: Potassium dichromate is reduced from Cr(VI) (orange) to Cr(III) (green).
Question 45
The noble gas used in filling deep-sea diving tanks along with Oxygen is:
A. Argon
B. Neon
C. Helium
D. Xenon
Answer: C. Helium
Explanation: Helium is used because it is less soluble in blood than nitrogen, preventing "the bends."
Question 46
A coordinate covalent bond is found in:
A. NaCl
B. MgCl2
C. NH4+
D. CH4
Answer: C. NH4+
Explanation: The Ammonium ion is formed when Ammonia (NH3) shares its lone pair with a Hydrogen ion (H+).
Question 47
Which of the following is an allotrope of Oxygen?
A. Ozone
B. Water
C. Carbon (IV) oxide
D. Sulfur
Answer: A. Ozone
Explanation: Ozone (O3) and Oxygen gas (O2) are the two primary allotropes of oxygen.
Question 48
The most abundant element in the universe is:
A. Oxygen
B. Nitrogen
C. Hydrogen
D. Helium
Answer: C. Hydrogen
Explanation: Hydrogen makes up about 75 percent of the elemental mass of the universe.
Question 49
Ethanoic acid reacts with Sodium trioxocarbonate (IV) to release:
A. Hydrogen gas
B. Oxygen gas
C. Carbon (IV) oxide gas
D. Nitrogen gas
Answer: C. Carbon (IV) oxide gas
Explanation: Reaction of any acid with a carbonate releases salt, water, and CO2.
Question 50
The ratio of the mass of a volume of gas to the mass of an equal volume of Hydrogen is its:
A. Relative atomic mass
B. Molar mass
C. Vapor density
D. Solubility
Answer: C. Vapor density
Explanation: Vapor density is defined as the mass of a certain volume of gas divided by the mass of the same volume of Hydrogen.