WAEC GCE Chemistry Questions and Answers: Objective, Theory, important topics and exam guide. To prepare adequately for WAEC GCE Chemistry, you need more than just memorizing formulas and equations. It Chemistry in WAEC GCE involves understanding chemical concepts, applying the appropriate formulas, interpreting laboratory results, writing correct chemical equations, and performing a wide range of calculations accurately.
The Chemistry WAEC GCE Questions in this article are original practice questions meant for revision purposes. It must be noted that objectives and essay (Paper 1 &2) practice questions are not actual examination questions, therefore they are not “leaked” questions or “unreleased” questions.
They help students to practice the types of WAEC GCE Chemistry examination questions likely to be set on senior secondary school chemistry, and so enable them to master the required competences and gain confidence ahead of their examinations.
Important Topics to Revise for WAEC GCE Chemistry:
A balanced revision plan should include sufficient practice of theory and application, including calculations, on the important topics listed below:
- Atomic Structure and the Periodic Table
- Chemical Bonding and Structure
- The Mole and Related Calculations
- Acids, Bases and Salts
- Oxidation, Reduction and Electrolysis
- Organic Chemistry
- Metals and their Compounds
- Chemical Equilibrium, Energy and Rates of Reaction
- Practical Chemistry and Qualitative Analysis
Atomic Structure and the Periodic Table
Revise atoms, subatomic particles, isotopes, electronic configuration, periodic trends and the relationship between an element’s position in the periodic table and its chemical properties.
Chemical Bonding and Structure
Understand ionic, covalent and metallic bonding, as well as how bonding affects properties such as melting point, electrical conductivity and solubility.
Mole Concept and Chemical Calculations
Candidates should be comfortable with relative atomic mass, molar mass, number of moles, empirical and molecular formulae, reacting masses, gas volumes and concentration calculations.
Acids, Bases and Salts
Revise indicators, pH, neutralisation, strong and weak acids, preparation of salts and the reactions and properties of common acids and bases.
Oxidation, Reduction and Electrolysis
Know how to identify oxidation and reduction, assign oxidation numbers and predict products formed during electrolysis where appropriate.
Organic Chemistry
Important areas include hydrocarbons, homologous series, functional groups, crude oil, alcohols, carboxylic acids, esters and polymers.
Metals and Their Compounds
Study the reactivity series, extraction of metals, corrosion, alloys and the characteristic reactions of common metal ions.
Chemical Equilibrium, Energy and Rates of Reaction
Understand reversible reactions, factors affecting equilibrium, exothermic and endothermic reactions, activation energy and factors affecting reaction rates.
Practical and Qualitative Analysis
Practise laboratory apparatus, separation techniques, gas tests, flame tests, identification of ions and observations from chemical experiments. Always distinguish an observation from the inference or conclusion drawn from it.
Useful Chemistry Formulas and Relationships
It is important for students to be familiar with calculations involved in chemistry, especially calculations using the following relationships:
Number of moles = Mass of substance / Molar mass
Concentration in mol/dm³ = Number of moles / Volume of solution in dm³
Percentage of an element in a compound = (Mass of element in 1 mol of compound / Molar mass of compound) x 100
Remember:
The volume of a gas at standard temperature and pressure is 24 dm³ unless a different value is stated in the question or the examination instructions.
It is important to be precise about the unit of measurement. Pay particular attention to calculations calling for answers in terms of 1000 cm³ = 1 , etc.
WAEC GCE Chemistry Objective Questions and Answers
Choose the most appropriate answer in each question.
Question 1.
Which particle determines the atomic number of an element?
A. Electron
B. Neutron
C. Proton
D. Nucleon
Answer: C. Proton
Explanation: The atomic number is equal to the number of protons in the nucleus of an atom.
Question 2.
An atom has 17 protons and 18 neutrons. What is its mass number?
A. 17
B. 18
C. 35
D. 36
Answer: C. 35
Explanation: Mass number = number of protons + number of neutrons = 17 + 18 = 35.
Question 3.
Which of the following electronic configurations represents an element in Group 2?
A. 2,8,1
B. 2,8,2
C. 2,8,7
D. 2,8,8
Answer: B. 2,8,2
Question 4.
The bond formed between sodium and chlorine in sodium chloride is mainly
A. covalent
B. ionic
C. metallic
D. coordinate
Answer: B. Ionic
Question 5.
Which property is generally associated with ionic compounds?
A. They always have low melting points.
B. They conduct electricity when molten or in aqueous solution.
C. They are composed only of non-metals.
D. They are always gases at room temperature.
Answer: B. They conduct electricity when molten or in aqueous solution.
Question 6.
What is the relative molecular mass of H₂SO₄? [H = 1, S = 32, O = 16]
A. 49
B. 64
C. 98
D. 100
Answer: C. 98
Working: (2 × 1) + 32 + (4 × 16) = 98.
Question 7.
How many moles are present in 18 g of water, H₂O? [H = 1, O = 16]
A. 0.5 mol
B. 1.0 mol
C. 2.0 mol
D. 18 mol
Answer: B. 1.0 mol
Working: Molar mass of H₂O = 18 g mol⁻¹.
Moles = 18/18 = 1 mol.
Question 8.
Which statement correctly describes an isotope?
A. Atoms of different elements with the same number of neutrons.
B.Atoms of the same element with different numbers of neutrons.
C. Atoms with different numbers of protons and electrons.
D.Atoms with the same mass number but different atomic numbers only.
Answer: B. Atoms of the same element with different numbers of neutrons.
Question 9.
Which gas turns limewater milky?
A. Ammonia
B. Carbon dioxide
C. Hydrogen
D. Oxygen
Answer: B. Carbon dioxide
Question 10.
A solution with a pH of 3 is best described as
A. strongly alkaline
B. weakly alkaline
C. acidic
D. neutral
Answer: C. Acidic
Question 11.
Which of the following is a strong acid?
A. Ethanoic acid
B. Carbonic acid
C. Hydrochloric acid
D. Ammonium hydroxide
Answer: C. Hydrochloric acid
Question 12.
The reaction between an acid and a base to form salt and water is called
A. oxidation
B. neutralisation
C. hydrolysis
D. electrolysis
Answer: B. Neutralisation
Question 13.
Which equation is correctly balanced?
A. H₂ + O₂ → H₂O
B. 2H₂ + O₂ → 2H₂O
C. H₂ + O → H₂O
D. H₂ + 2O₂ → H₂O
Answer: B. 2H₂ + O₂ → 2H₂O
Question 14.
Oxidation can be defined as
A. gain of electrons
B. loss of electrons
C. gain of neutrons
D. loss of protons
Answer: B. Loss of electrons
Question 15.
In the reaction Zn + CuSO₄ → ZnSO₄ + Cu, zinc acts as
A. an oxidising agent only
B. a reducing agent
C. an acid
D. a catalyst
Answer: B. A reducing agent
Explanation: Zinc loses electrons and causes copper(II) ions to gain electrons.
Question 16.
Which metal is most likely to displace copper from copper(II) sulfate solution?
A. Silver
B. Gold
C. Zinc
D. Copper
Answer: C. Zinc
Question 17.
The main purpose of adding a catalyst to a reaction is to
A. increase the amount of product at equilibrium in every reaction
B. lower the activation energy and increase the reaction rate
C. increase the mass of the reactants
D. change the chemical equation permanently
Answer: B. Lower the activation energy and increase the reaction rate
Question 18.
Which factor generally increases the rate of reaction between a solid and a solution?
A. Using larger pieces of the solid
B. Lowering the temperature
C. Increasing the surface area of the solid
D. Decreasing the concentration of the solution
Answer: C. Increasing the surface area of the solid
Question 19.
An exothermic reaction is one that
A. absorbs heat from the surroundings
B. releases heat to the surroundings
C. cannot occur without electricity
D. always produces a gas
Answer: B. Releases heat to the surroundings
Question 20.
Which separation technique is most suitable for obtaining pure water from a salt solution?
A. Filtration
B. Evaporation to dryness
C. Simple distillation
D. Decantation
Answer: C. Simple distillation
Question 21.
Which apparatus is most suitable for accurately measuring a fixed volume of 25.0 cm³ of a solution?
A. Beaker
B. Measuring cylinder
C. Pipette
D. Evaporating dish
Answer: C. Pipette
Question 22.
A substance changes directly from a solid to a gas on heating. The process is known as
A. condensation
B. sublimation
C. distillation
D. crystallisation
Answer: B. Sublimation
Question 23.
Which of the following is a saturated hydrocarbon?
A. Ethene
B. Ethyne
C. Ethane
D. Benzene
Answer: C. Ethane
Question 24.
The general formula for alkanes is
A. CₙH₂ₙ
B. CₙH₂ₙ₊₂
C. CₙH₂ₙ₋₂
D. CₙHₙ
Answer: B. CₙH₂ₙ₊₂
Question 25.
Which reagent can be used to distinguish between an alkane and an alkene?
A. Limewater
B. Acidified potassium manganate(VII) or bromine water
C. Sodium chloride solution
D. Distilled water
Answer: B. Acidified potassium manganate(VII) or bromine water
Question 26.
Ethanol belongs to which homologous series?
A. Alkanes
B. Alkenes
C. Alcohols
D. Carboxylic acids
Answer: C. Alcohols
Question 27.
The functional group present in ethanoic acid is
A. –OH only
B. –COOH
C. –CHO
D. –NH₂
Answer: B. –COOH
Question 28.
A compound formed from an alcohol and a carboxylic acid is generally known as
A. an ester
B. an alkane
C. a salt only
D. an amine
Answer: A. An ester
Question 29.
Which of the following is an alloy?
A. Copper
B. Iron
C. Brass
D. Aluminium
Answer: C. Brass
Question 30.
Rusting of iron requires
A. nitrogen and sunlight
B. oxygen and water
C. carbon dioxide only
D. hydrogen and water
Answer: B. Oxygen and water
Question 31.
Which gas is produced when a reactive metal reacts with a dilute acid?
A. Carbon dioxide
B. Chlorine
C. Hydrogen
D. Oxygen
Answer: C. Hydrogen
Question 32.
A gas that relights a glowing splint is
A. hydrogen
B. oxygen
C. carbon dioxide
D. ammonia
Answer: B. Oxygen
Question 33.
Which observation is expected when aqueous sodium hydroxide is added to a solution containing Cu²⁺ ions?
A. A blue precipitate forms
B. A white precipitate forms
C. A green gas is evolved
D. No visible change occurs
Answer: A. A blue precipitate forms
Question 34.
The flame colour commonly associated with sodium ions is
A. blue-green
B. crimson red
C. yellow
D. lilac
Answer: C. Yellow
Question 35.
During electrolysis, reduction occurs at the
A. anode
B. cathode
C. electrolyte only
D. salt bridge
Answer: B. Cathode
Question 36.
The empirical formula of a compound represents
A. the exact number of atoms in a molecule
B. the simplest whole-number ratio of atoms in the compound
C. the total mass of the compound
D. the electronic configuration of the compound
Answer: B. The simplest whole-number ratio of atoms in the compound
Question 37.
If 0.50 mol of NaOH is dissolved to make 250 cm³ of solution, what is the concentration?
A. 0.125 mol dm⁻³
B. 0.50 mol dm⁻³
C. 2.0 mol dm⁻³
D. 125 mol dm⁻³
Answer: C. 2.0 mol dm⁻³
Working: 250 cm³ = 0.250 dm³.
Concentration = 0.50/0.250 = 2.0 mol dm⁻³.
Question 38.
Which change would shift the equilibrium of a gaseous reaction toward the side with fewer moles of gas?
A. Decreasing pressure
B. Increasing pressure
C. Removing a catalyst
D. Adding an inert solid
Answer: B. Increasing pressure
Question 39.
Which statement about dynamic equilibrium is correct?
A. The reaction has stopped completely.
B. The concentrations of reactants and products must be equal.
C. The forward and reverse reactions occur at equal rates in a closed system.
D. Only the forward reaction occurs.
Answer: C. The forward and reverse reactions occur at equal rates in a closed system.
Question 40.
Which practice is most important when recording results from a Chemistry experiment?
A. Altering unusual results to fit expectations
B. Recording observations accurately and honestly
C. Ignoring units in measurements
D. Estimating all measurements without apparatus
Answer: B. Recording observations accurately and honestly
RECOMMENDED: WAEC GCE Second Series Timetable and PDF download
WAEC GCE Chemistry Theory and Essay Practice Questions with Answers
The following questions are designed to develop calculation, explanation and scientific reasoning skills. In an examination, candidates should show relevant working and write balanced equations where required.
Question 41.
(a) Define the term mole.
(b) Calculate the number of moles in 11 g of carbon dioxide, CO₂. [C = 12, O = 16]
(c) Calculate the mass of 0.25 mol of sodium carbonate, Na₂CO₃. [Na = 23, C = 12, O = 16]
Answer
(a) A mole is the amount of substance containing the same number of specified particles as there are atoms in 12 g of carbon-12.
(b) Calculation of moles of CO₂
Molar mass of CO₂:
= 12 + (2 × 16)
= 44 g mol⁻¹
Number of moles:
= mass / molar mass
= 11/44
= 0.25 mol
(c) Calculation of mass of Na₂CO₃
Molar mass:
= (2 × 23) + 12 + (3 × 16)
= 106 g mol⁻¹
Mass = number of moles × molar mass
= 0.25 × 106
= 26.5 g
Question 42.
(a) Explain the difference between ionic and covalent bonding.
(b) Explain why solid sodium chloride does not conduct electricity, whereas molten sodium chloride does.
Answer
(a) Ionic bonding involves the electrostatic attraction between oppositely charged ions formed after the transfer of electrons. Covalent bonding involves the sharing of electrons between atoms.
(b) In solid sodium chloride, the sodium and chloride ions are held in fixed positions in a crystal lattice and cannot move to carry electric current. When sodium chloride is molten, the ions become mobile and can move toward the electrodes, allowing the molten substance to conduct electricity.
Question 43.
A student reacts 5.0 g of calcium carbonate with excess dilute hydrochloric acid.
(a) Write a balanced chemical equation for the reaction.
(b) Calculate the number of moles of calcium carbonate used. [Ca = 40, C = 12, O = 16]
(c) State the gas produced and describe a chemical test for it.
Answer
(a) Balanced equation:
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
(b) Calculation
Molar mass of CaCO₃:
= 40 + 12 + (3 × 16)
= 100 g mol⁻¹
Moles = 5.0/100 = 0.050 mol
(c) The gas produced is carbon dioxide.
A suitable test is to pass the gas through limewater. The limewater turns milky or cloudy due to the formation of calcium carbonate.
Question 44.
(a) Define oxidation and reduction in terms of electron transfer.
(b) For the reaction below, identify the species oxidised and the species reduced:
Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)
Answer
(a)
- Oxidation is the loss of electrons.
- Reduction is the gain of electrons.
(b) Zinc changes from Zn to Zn²⁺, meaning it loses electrons:
Zn → Zn²⁺ + 2e⁻
Therefore, zinc is oxidised.
Copper(II) ions gain electrons:
Cu²⁺ + 2e⁻ → Cu
Therefore, Cu²⁺ ions are reduced.
This is a redox reaction because oxidation and reduction occur simultaneously.
Question 45.
(a) Explain what is meant by a homologous series.
(b) State two characteristics of members of a homologous series.
(c) Write the molecular formula of the alkane containing four carbon atoms and name it.
Answer
(a) A homologous series is a family of organic compounds with the same functional group and general formula, showing similar chemical properties.
(b) Two characteristics include:
- Successive members differ by a –CH₂– unit.
- Members have similar chemical properties because they contain the same functional group.
Other acceptable characteristics include a gradual change in physical properties and a common general formula.
(c) Alkanes have the general formula CₙH₂ₙ₊₂.
For n = 4:
C₄H₁₀
The compound is butane.
Question 46.
A student is given three colourless solutions labelled P, Q and R. The following observations are made:
- P turns blue litmus paper red.
- Q turns red litmus paper blue.
- R has no effect on either red or blue litmus paper.
(a) Classify P, Q and R as acidic, alkaline or neutral.
(b) Explain how the student could use a pH indicator or pH meter to obtain further information.
(c) State why indicator observations alone may not identify the exact chemical substance present.
Answer
(a)
- P is acidic.
- Q is alkaline.
- R is likely neutral under the test conditions.
(b) A universal indicator could be added to separate samples to estimate their pH from the colour produced. A pH meter could provide a more precise numerical pH value when properly used.
(c) An indicator mainly provides information about acidity or alkalinity. Different substances can have similar pH values, so further chemical tests would be needed to identify the exact substance.
Question 47.
(a) Explain three factors that can affect the rate of a chemical reaction.
(b) A student wants to investigate the effect of temperature on the reaction between a solid and a solution. State two variables that should be kept constant.
(c) Explain why controlling variables is important in a fair experiment.
Answer
(a) Factors affecting reaction rate include:
- Temperature: Higher temperature generally gives particles more kinetic energy and increases the frequency of successful collisions.
- Concentration: A higher concentration generally means more reacting particles are present in a given volume, increasing collision frequency.
- Surface area: Smaller particles provide a larger surface area for reaction, increasing the opportunities for collisions.
A catalyst can also increase reaction rate by providing an alternative reaction pathway with a lower activation energy.
(b) Variables that could be kept constant include:
- Mass or surface area of the solid.
- Volume and concentration of the solution.
- Type of reactants used.
(c) Controlling other variables helps ensure that changes in the reaction rate are mainly due to the variable being investigated. This improves the reliability and fairness of the experiment.
Practical Chemistry Skills Candidates Should Practise
Chemistry practical questions often require candidates to describe observations and apply Laboratory skills. Some key practical skills to develop include:
- Reporting colour changes, precipitates and gases accurately
- Making a distinction between observations and inferences
- Testing for common gases using correct reagents
- Carrying out filtration, crystallization and distillation correctly
- Using laboratory apparatus correctly and giving reasons for the use of specific laboratory equipment
- Giving reasons for observations or unexpected results
- Reporting measurements from laboratory instruments correctly using the correct units
- Applying appropriate laboratory safety rules and handling laboratory chemicals correctly
- When stating observations during chemistry practicals, avoid giving vague statements, for instance: “a reaction took place”. Give specific observations like in “a blue precipitate formed”
Common mistakes to avoid when answering chemistry questions
1. Forgetting to balance chemical equations.
Make sure the number of atoms of each element is equal on either side of a chemical reaction before attempting to answer any question on chemical calculations.
2. Ignoring units when reporting calculated values.
Make sure you convert volumes of liquids to the right units and always state the units of any quantity you report.
3. Memorizing without understanding.
It is important to memorize chemical equations, but make sure you understand them.
4. Confusing observations and inferences.
If the question asks you to state observations, you should not mention the ions present in a solution unless you are specifically asked to state the inferences from your observations. Observations should be what you see, smell or feel during an experiment. Inferences are therefore conclusions you can draw from your observations and should only be stated if asked for explicitly.
5. Skipping calculation steps by reporting only final answers.
Always show your working and the formulas used to calculate an answer. Even if your final answer is wrong, you may still get marks for showing correct steps or intermediate values.
How to revise effectively for WAEC GCE Chemistry
Your WAEC GCE chemistry revision should be comprehensive and include calculations, reactions and practical observations.
It is best to start by mastering concepts that are not well understood and then proceed to attempt calculations and write down chemical reactions to test understanding. Practise calculations until they begin to come naturally and the correct formulas and units are almost automatically selected when solving a problem.
For organic and inorganic chemistry, practise writing down chemical equations to relate properties of substances to the reactions they undergo.
For practicals, it is best to learn the significance of specific observations. This prevents vague statements when describing what happens during an experiment.
Most importantly, remember to attempt WAEC GCE chemistry past questions under timed conditions and always review your answers to ensure that chemical equations are balanced correctly, the correct units are used and that explanations of observations are logical.
Frequently Asked Questions About WAEC GCE Chemistry Questions And Answers PDF
Are the questions in this article official WAEC GCE Chemistry questions?
The questions in this article are not official WAEC GCE Chemistry questions but practice questions for revision purposes only. The questions are not presented as official, leaked or genuine WAEC examination questions.
Which topics should I revise for WAEC GCE Chemistry?
It is best to revise calculations, chemical reactions, chemical properties, bonding and atomic structure, acids and bases, organic Chemistry, electrochemistry, and practical or qualitative analysis. A good WAEC GCE revision schedule will ensure comprehensive coverage of all topics in the syllabus rather than focusing on selected topics.
How can I revise calculations for WAEC GCE Chemistry?
The best way to revise calculations for WAEC GCE Chemistry is to practise calculations regularly. For instance, revise calculations on the mole concept and chemical calculations. Always show working and the correct formulas and units for any calculation. Remember to always convert units of volume when carrying out calculations.
Should I memorize all chemical equations for WAEC GCE Chemistry?
It is good to memorize chemical reactions, but you should focus on understanding chemical reactions rather than memorizing them.
How can I revise for chemistry practicals?
It is best to learn common observations of experiments, gas tests and simple chemical tests for ions, and separation methods. You should also learn common laboratory apparatus and how to carry out simple chemical calculations.
Final advice
It is important to understand concepts and how to apply them to problem solve during exam revision. You should also revise calculations step-by-step and be able to write chemical equations correctly and confidently.
Using official practice questions such as these alongside standard revision guides and books will help improve your performance in WAEC GCE Chemistry. It is important to avoid websites and individuals claiming to have access to official or real WAEC examination questions or materials. Revising past papers alongside class notes and textbooks is the best way to prepare for the examination.
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