1.
Mole concept
How many moles are in 500 g of CaCO₃? (Ca = 40, C = 12, O = 16)
Answer: A. Moles = mass ÷ molar mass = 500 ÷ 100 = 5 mol.
WAEC GCE Chemistry practice questions
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The GCE is the version of the school-leaving exam for private candidates, usually held towards the end of the year. It follows the same syllabus as the May/June exam, with objective and theory papers.
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2.
Gas laws
A gas occupies 60 cm³ at a pressure of 800 mmHg. Find its volume at 600 mmHg, temperature remaining constant.
Answer: C. Boyle's law: P₁V₁ = P₂V₂, so V₂ = 800 × 60 ÷ 600 = 80 cm³.
3.
Solutions
Express 0.1 mol/dm³ Na₂CO₃ solution in g/dm³. (Na = 23, C = 12, O = 16)
Answer: C. Mass concentration = molar concentration × molar mass = 0.1 × 106 = 10.6 g/dm³.
4.
Electrolysis
A current of 5 A flows for 22 minutes. Find the quantity of electricity passed.
Answer: D. Q = It = 5 × (22 × 60) = 6,600 C (time must be in seconds).
5.
Acids, bases and salts
What is the pH of 0.01 mol/dm³ hydrochloric acid? (Assume it ionises completely.)
Answer: B. [H⁺] = 0.01 = 10⁻² mol/dm³, and pH = −log[H⁺] = 2.
6.
Chemical formulae
Calculate the percentage by mass of oxygen in CaCO₃. (Ca = 40, C = 12, O = 16)
Answer: C. % of oxygen = (mass of oxygen in one formula unit ÷ molar mass) × 100 = 48%.
7.
Gases
A test for hydrogen chloride is that the gas
Answer: C. Hydrogen chloride forms dense white fumes with ammonia.
8.
Organic chemistry
Which homologous series has the functional group –COOH (carboxyl)?
Answer: A. The functional group of alkanoic acids is –COOH (carboxyl).
9.
Periodic table
Which of these is a noble gas?
Answer: C. Argon is in Group 0 (Group 18), the noble gases.
10.
Atomic structure
What is the atomic number of carbon?
Answer: B. Carbon has 6 protons, so its atomic number is 6.
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Questions in the MyGradePrep bank for each topic.
| Topic | Questions |
|---|---|
| Mole concept | 226 |
| Gas laws | 120 |
| Periodic table | 69 |
| Solutions | 67 |
| Atomic structure | 61 |
| States of matter | 61 |
| Electrolysis | 61 |
| Solubility | 60 |
| Chemical formulae | 40 |
| Organic chemistry | 38 |
| Acids, bases and salts | 18 |
| Redox | 18 |
| Gases | 14 |
| Separation techniques | 10 |