Sample WAEC-style Practice Questions (Original Content)
WAEC Style
Question 1
Which of the following separation techniques is most suitable for obtaining pure water from sea water?
A. Filtration
B. Evaporation
C. Distillation
D. Chromatography
Answer: C. Distillation
Explanation: Distillation involves boiling the water to create steam and then condensing it back into a liquid, leaving salts behind.
Question 2
The atomic number of an element is 13. What is its electronic configuration?
A. 2, 8, 1
B. 2, 8, 2
C. 2, 8, 3
D. 2, 8, 4
Answer: C. 2, 8, 3
Explanation: The first shell holds 2, the second holds 8, and the remaining 3 go to the third shell.
Question 3
Atoms of the same element with the same atomic number but different mass numbers are called:
A. Isomers
B. Allotropes
C. Isotopes
D. Isobars
Answer: C. Isotopes
Explanation: Isotopes have the same number of protons but different numbers of neutrons.
Question 4
Which of the following represents a physical change?
A. Burning of wood
B. Rusting of iron
C. Melting of candle wax
D. Souring of milk
Answer: C. Melting of candle wax
Explanation: Melting is a change of state (solid to liquid) and can be reversed; no new substance is formed.
Question 5
Which of the following is a neutral oxide?
A. Carbon (IV) oxide
B. Sulfur (IV) oxide
C. Nitrogen (II) oxide
D. Sodium oxide
Answer: C. Nitrogen (II) oxide
Explanation: NO, N2O, and CO are common neutral oxides that do not react with acids or bases.
Question 6
The bond formed when two atoms share a pair of electrons is called:
A. Ionic bond
B. Covalent bond
C. Metallic bond
D. Hydrogen bond
Answer: B. Covalent bond
Explanation: Covalent bonding involves the sharing of valence electrons between non-metal atoms.
Question 7
Which of the following gas laws states that the volume of a fixed mass of gas is inversely proportional to its pressure at constant temperature?
A. Charles's Law
B. Boyle's Law
C. Graham's Law
D. Avogadro's Law
Answer: B. Boyle's Law
Explanation: Boyle's law is represented by the formula P1V1 = P2V2.
Question 8
What is the oxidation number of sulfur in H2SO4?
A. +2
B. +4
C. +6
D. -2
Answer: C. +6
Explanation: 2(1) + S + 4(-2) = 0. 2 + S - 8 = 0. S = +6.
Question 9
A solution with a pH of 3 is described as:
A. Weakly acidic
B. Strongly acidic
C. Weakly alkaline
D. Strongly alkaline
Answer: B. Strongly acidic
Explanation: pH values from 0 to 3 are generally considered strongly acidic.
Question 10
The process of a solid changing directly into a gas without passing through the liquid state is:
A. Evaporation
B. Sublimation
C. Condensation
D. Melting
Answer: B. Sublimation
Explanation: Iodine and Ammonium chloride are common substances that undergo sublimation.
Question 11
Which of the following is an example of an alloy?
A. Iron
B. Gold
C. Bronze
D. Copper
Answer: C. Bronze
Explanation: Bronze is an alloy consisting primarily of copper, usually with tin as the main additive.
Question 12
The main constituent of natural gas is:
A. Ethane
B. Methane
C. Propane
D. Butane
Answer: B. Methane
Explanation: Natural gas is composed of about 90 percent methane (CH4).
Question 13
Calculate the molar mass of CaCO3. (Ca=40, C=12, O=16)