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WAEC Chemistry: practice questions.
12 free questions with answers and explanations, plus the topics to revise.
Below are free WAEC Chemistry practice questions with answers and explanations. They are original eZine questions, written and reviewed by teachers in the style of the WAEC WASSCE; we do not publish past questions. eZine's published WAEC Chemistry bank holds 397 questions across 40 topics (counted 29 October 2026); the largest topics are Acids, Bases and Salts, Electrolysis, Mass-volume relationship.
eZine's WAEC subject mock uses 50 questions in 60 minutes estimated. WAEC sets the objective paper's length per subject and publishes it in each subject's syllabus; eZine holds no WAEC paper figures yet, so this is a practice default.
WAEC Chemistry practice questions
Choose an option to check it, or open the answer. Each is an eZine practice question (original, teacher-reviewed).
Question 1 · Gas Laws
A gas occupies 200 cm^3 at 27 °C. What will its volume be at 127 °C if the pressure is kept constant? [0 °C = 273 K]
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Answer: B. 267 cm^3
Charles' law needs absolute temperatures: T1 = 27 + 273 = 300 K and T2 = 127 + 273 = 400 K. V2 = 200 x 400/300 = 266.7 cm^3, i.e. 267 cm^3. 941 cm^3 uses degrees Celsius (200 x 127/27); 150 cm^3 inverts the temperature ratio; 200 cm^3 assumes the volume is unchanged.
eZine practice question (original, teacher-reviewed)
Question 2 · Hydrocarbons (alkanes, alkenes and alkynes)
A hydrocarbon decolourises bromine water rapidly at room temperature. The hydrocarbon is MOST likely
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Answer: C. ethene
Ethene has a C=C double bond and undergoes addition with bromine, removing the orange colour. Ethane and methane are saturated (react with bromine only in light, slowly, by substitution); benzene does not decolourise bromine water under these conditions.
eZine practice question (original, teacher-reviewed)
Question 3 · Entrepreneurship in Chemistry
Which of the following is a chemistry-related business that a school leaver in Onitsha could start with small capital?
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Answer: C. Production of liquid soap and disinfectant
Liquid soap and disinfectant production uses chemistry (saponification, mixing of surfactants and antiseptics). The other businesses do not depend on chemical knowledge.
eZine practice question (original, teacher-reviewed)
Question 4 · Oxidation-reduction (REDOX) reactions
In which of the following does sulphur have the HIGHEST oxidation number?
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Answer: B. H2SO4
S in H2SO4: 2 + x − 8 = 0 → +6. SO2: +4; H2S: −2; Na2S2O3: 2 + 2x − 6 = 0 → +2.
eZine practice question (original, teacher-reviewed)
Question 5 · Gas Laws
A given volume of oxygen diffuses through a porous plug in 20 s. The same volume of gas X diffuses through the same plug in 40 s under identical conditions. The relative molecular mass of X is [O = 16]
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Answer: B. 128
Time is proportional to √M: tX/tO2 = √(MX/32), so 40/20 = 2 = √(MX/32), giving MX = 4 × 32 = 128. 64 uses a direct (not square) relationship; 16 and 8 invert the relationship (the slower gas must be heavier).
eZine practice question (original, teacher-reviewed)
Question 6 · Ionic theory
Which of the following metals is the STRONGEST reducing agent?
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Answer: A. Potassium
Potassium is highest in the electrochemical series, so it loses electrons most readily. Zinc is a moderate reducing agent; copper and silver are low in the series and are poor reducing agents.
eZine practice question (original, teacher-reviewed)
Question 7 · Chemical Equilibrium
A reversible reaction is said to be in dynamic equilibrium when
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Answer: A. the rates of the forward and backward reactions are equal
At dynamic equilibrium both reactions continue at equal rates, so concentrations stay constant. Reactants are not all used up; concentrations are constant but not necessarily equal; neither reaction stops (hence "dynamic").
eZine practice question (original, teacher-reviewed)
Question 8 · Alkanols
What is the IUPAC name of CH3CH2CH(OH)CH3?
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Answer: D. butan-2-ol
The chain has four carbons (butan-) and the -OH group is on carbon 2 when numbered from the end nearer to it: butan-2-ol. It is a secondary alkanol. butan-3-ol numbers from the wrong end; butan-1-ol has the -OH on the end carbon; butan-2-one is a ketone (C=O), not an alkanol.
eZine practice question (original, teacher-reviewed)
Question 9 · Alkanols
The IUPAC name of CH3CH(OH)CH2CH3 is
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Answer: B. butan-2-ol
The longest chain has four carbons (butan-) and is numbered to give –OH the lowest locant: carbon 2. "Butan-3-ol" numbers from the wrong end; "2-hydroxybutane" is not the alkanol name; butan-1-ol has –OH on the terminal carbon.
eZine practice question (original, teacher-reviewed)
Question 10 · Atomic Structure
Which particle was shown by Rutherford's gold-foil experiment to be concentrated in a tiny, dense, positively charged centre of the atom?
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Answer: B. The nucleus
Most alpha particles passed straight through but a few were deflected sharply, showing that the positive charge and most of the mass are in a tiny nucleus. Electrons occupy the large surrounding space; neutrons are uncharged and were discovered later by Chadwick; the valence shell is the outermost electron shell.
eZine practice question (original, teacher-reviewed)
Question 11 · Entrepreneurship in Chemistry
In a business plan for a pomade-making venture, the section that estimates the cost of petroleum jelly, perfume and containers is the
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Answer: A. financial plan
The financial plan sets out start-up costs, operating costs, pricing and expected profit. The marketing plan covers customers, promotion and distribution; the executive summary is a brief overview; the organisational plan covers staff and management.
eZine practice question (original, teacher-reviewed)
Question 12 · Chemical Equilibrium
Consider H2(g) + I2(g) ⇌ 2HI(g). Increasing the total pressure at constant temperature will
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Answer: A. have no effect on the equilibrium position
There are 2 moles of gas on each side, so pressure does not favour either side. Shifts left or right would only occur if the gas moles differed; Kc changes only with temperature.
eZine practice question (original, teacher-reviewed)
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Practise free on eZine →Topics in eZine's WAEC Chemistry practice bank
- Acids, Bases and Salts (57)
- Electrolysis (20)
- Mass-volume relationship (20)
- Hydrocarbons (alkanes, alkenes and alkynes) (19)
- Oxidation-reduction (REDOX) reactions (19)
- Gas Laws (17)
- Nitrogen (14)
- The Periodic Table and the periodicity of elements (14)
- Water (14)
- Sulphur (13)
- Atomic Structure (12)
- Symbols, Formulae and Equations (12)
- Alkanols (11)
- Chemical Bonds (11)
- Chemical Equilibrium (11)
- Standard Separation Techniques (11)
- Oxygen (10)
- Elements, Compounds and Mixtures (9)
- Carbon and its Compounds (8)
- Hydrogen (8)
- Particulate Nature of Matter (8)
- Chemical Combination (7)
- Chemical industry (7)
- Halogens (7)
Published questions per topic, counted 29 October 2026. eZine does not reproduce WAEC's own Chemistry syllabus here; check the official syllabus with your school or at the WAEC website.