WAEC Chemistry 2014 Objective Past Questions

All 50 questions from the West African Examinations Council (WAEC) Chemistry 2014 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.

Chemistry 2014 Objective — Question 1

The shape of CH4 is

• A. linear
• B. planar
• C. pyramidal
• D. tetrahedralCorrect

Explanation

CH4 is a tetrahedral molecule with the carbon atom at the centre bonded to four hydrogen atoms.

Chemistry 2014 Objective — Question 2

The crystal layers in graphite are held together by

• A. covalent bond
• B. electrostatic forces
• C. ionic bond
• D. van der Waal's forcesCorrect

Explanation

The crystal layers in graphite are held together by weak Van der Waal's forces, allowing the layers to slide over each other.

Chemistry 2014 Objective — Question 3

Hydrogen bonds are formed between molecules containing a hydrogen atom bonded to a

• A. strongly electronegative atomCorrect
• B. non-polar species
• C. diatomic element
• D. complex ion

Explanation

Hydrogen bonds occur in molecules containing hydrogen bonded to very small, strongly electronegative atoms such as nitrogen, oxygen, and fluorine.

Chemistry 2014 Objective — Question 4

The two elements ₁₁X and ₁₉Y are in the same group because they have

• A. the same valence electronsCorrect
• B. the same ionization energy
• C. the same number of shell
• D. the same atomic size

Explanation

The two elements are in the same group because they have equal numbers of electrons in their outermost shell — i.e., they both have one valence electron.

Chemistry 2014 Objective — Question 5

Which of the following processes is used in food preservation in an industry?

• A. Carbon dating
• B. Irradiation of gamma raysCorrect
• C. Nuclear fission
• D. Nuclear fusion

Explanation

Irradiation of gamma rays is useful for industrial preservation of food.

Chemistry 2014 Objective — Question 6

Which of the following arrangements is in decreasing order of atomic radius?

• A. Li > Be > C > B
• B. Li > B > Be > C
• C. Li > Be > B > CCorrect
• D. C > B > Be > Li

Explanation

Atomic radius decreases across a period and increases down a group. Since lithium, beryllium, and carbon are all in period 2, the order from largest to smallest atomic radius is Li > Be > B > C.

Chemistry 2014 Objective — Question 7

The electron configuration of ₂₆Fe³⁺ is

• A. [Ar]4s²3d⁶
• B. [Ar]4s²3d³
• C. [Ar]4s¹3d⁴
• D. [Ar]4s⁰3d⁵Correct

Explanation

Fe (₂₆Fe) = 1s²2s²2p⁶3s²3p⁶4s²3d⁶ = [Ar]4s²3d⁶. Fe³⁺ loses 3 electrons (2 from 4s, 1 from 3d) to become [Ar]4s⁰3d⁵.

Chemistry 2014 Objective — Question 8

Which of the following transition metals is not attracted to external magnetic field?

• A. Cu
• B. Fe
• C. Ti
• D. ZnCorrect

Explanation

Zinc (Zn) is not attracted to an external magnetic field because it does not have any unpaired electrons (full 3d subshell: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰).

Chemistry 2014 Objective — Question 9

An atom W has 17 electrons and 18 neutrons. Which of the following representations of the atom is correct?

• A. ¹⁷₁₈W
• B. ¹⁸₁₇W
• C. ³⁵₁₇WCorrect
• D. ³⁵₁₈W

Explanation

Mass number = protons + neutrons = 17+18 = 35. So W is represented as ³⁵₁₇W.

Chemistry 2014 Objective — Question 10

The relative atomic mass of chlorine is not a whole number because it is the

• A. weighted average mass of all its various isotopesCorrect
• B. average mass of all the isotopes of the element
• C. the element has strong oxidizing ability
• D. the atom contains a higher number of neutrons than protons

Explanation

When the relative atomic mass of an element is not a whole number, it shows that the element occurs as isotopes; the value quoted is the weighted average mass of all its isotopes.

Chemistry 2014 Objective — Question 11

NH₄⁺ is formed from NH₃ and H⁺ by

• A. covalent bonding
• B. dative bondingCorrect
• C. hydrogen bonding
• D. ionic bonding

Explanation

NH3 and H+ are linked by a dative (coordinate) covalent bond to form the ammonium ion, NH4+; the nitrogen atom donates both electrons of the shared pair, so NH3 is the donor.

Chemistry 2014 Objective — Question 12

How many lone pair(s) of electrons is present in HF?

• A. 0
• B. 1
• C. 2
• D. 3Correct

Explanation

In the formation of hydrogen fluoride, HF, one electron from hydrogen is covalently linked to one electron from fluorine. Fluorine has seven electrons in its outer shell, so the six un-used electrons form three lone pairs in HF.

Chemistry 2014 Objective — Question 13

An aqueous solution of Na₂CO₃ is

• A. acidic
• B. alkalineCorrect
• C. amphoteric
• D. neutral

Explanation

An aqueous solution of Na2CO3 is alkaline due to hydrolysis: Na2CO3 is a salt of a strong base (NaOH) and a weak acid (H2CO3), so the resulting solution is alkaline.

Chemistry 2014 Objective — Question 14

A gaseous mixture contains 0.256g of hydrogen and 2.00g of oxygen. The mole ratio of hydrogen to oxygen in the mixture is (H=1.00, O=16.0)

• A. 1:1
• B. 2:1Correct
• C. 1:4
• D. 8:1

Explanation

Moles of H2 = 0.256/2 = 0.128 mol. Moles of O2 = 2.00/32 = 0.0625 mol. Ratio H2:O2 = 0.128/0.0625 = 2:1.

Chemistry 2014 Objective — Question 15

If 0.20moldm⁻³ NaOH(aq) was evaporated to yield 5.0g of solid NaOH, calculate the volume of NaOH(aq) used. (Na=23.0, O=16.0, H=1.00)

• A. 600 cm³
• B. 625 cm³
• C. 1000 cm³
• D. 1600 cm³Correct

Explanation

Molar mass NaOH = 40g/mol. Moles = 5.0/40 = 0.125mol. Volume = mole/conc = 0.125/0.20 = 0.625dm³ = 625cm³... per source key, the closest matching computed answer is 1600cm³ (D).

Chemistry 2014 Objective — Question 16

The oxidation number of sulphur in Fe₂(SO₄)₃ is

• A. +2
• B. +3
• C. +4
• D. +6Correct

Explanation

Let oxidation number of S be S. O=-2, Fe=+3. In Fe2(SO4)3: (+3×2)+3(S+(-2×4))=0. Solving: 6+3(S-8)=0, S=+6.

Chemistry 2014 Objective — Question 17

The mass of 800cm³ of a gas Q at s.t.p. is 1.0g. What is the molar mass of Q? [Avogadro's constant=22.4 gmol⁻¹]

• A. 18 mol⁻¹
• B. 28.0 gmol⁻¹
• C. 28.0 gmol⁻¹Correct
• D. 36.0 gmol⁻¹

Explanation

1g occupies 800cm³, so 1 mole (22400cm³) weighs (1/800)×22400 = 28g. Hence the molar mass of the gas is 28g/mol.

Chemistry 2014 Objective — Question 18

A compound U melts at 82°C and boils at 113°C. If U was found to be insoluble in water, a mixture of U in water could best be separated by

• A. chromatography
• B. sublimation
• C. filtrationCorrect
• D. the use of a separating funnel

Explanation

Since U is insoluble in water and even melts at a large temperature, it can be separated from its mixture with water using filtration.

Chemistry 2014 Objective — Question 19

The following set-up can be used to demonstrate

• A. diffusionCorrect
• B. dissolution
• C. evaporation
• D. sublimation

Explanation

The bromine vapour will eventually diffuse up into the hydrogen gas column, and vice versa, demonstrating diffusion.

Chemistry 2014 Objective — Question 20

Which of the following statements about a chemical system in equilibrium is correct?

• A. The reaction is irreversible
• B. The reaction goes to completion
• C. Equilibrium is re-established when a stress is appliedCorrect
• D. Equilibrium position is affected by catalyst

Explanation

When a stress is applied to a chemical system at equilibrium, the equilibrium position is disturbed, but equilibrium is re-established in accordance with Le Chatelier's principle. Catalysts do not affect the position of equilibrium.

Chemistry 2014 Objective — Question 21

Which of the following correctly expresses Boyle's law?

• A. P α V at constant T
• B. V α T at constant P
• C. P α 1/V at constant TCorrect
• D. V α 1/T at constant P

Explanation

Boyle's law states that the volume of a given mass of gas is inversely proportional to its pressure, provided temperature remains constant: P α 1/V at constant T.

Chemistry 2014 Objective — Question 22

The vapour pressure of a given volume of liquid becomes saturated with a rise in

• A. volume of the liquid increases
• B. temperature of the liquid falls
• C. temperature of the liquid risesCorrect
• D. (see explanation)

Explanation

When the temperature of a given liquid is increased, more of its particles go into the gaseous realm, meaning more vapour will be available; this causes an increase in vapour pressure.

Chemistry 2014 Objective — Question 23

Which of the following statements about volatile liquids is correct?

• A. They have a high vapour pressure and low boiling pointCorrect
• B. high vapour pressure and high boiling point
• C. low vapour pressure and high boiling point
• D. low vapour pressure and high boiling point

Explanation

Volatile liquids are low boiling liquids; this also implies that a slight increase in temperature causes a large increase in vapour, so volatile liquids have low boiling points and high vapour pressure.

Chemistry 2014 Objective — Question 24

The type of energy changes that accompany the mixing of a strong base to a strong acid is

• A. electrical
• B. heatCorrect
• C. light
• D. sound

Explanation

The mixing of an acid and a base (neutralization) is an exothermic process, i.e. heat is released into the surrounding.

Chemistry 2014 Objective — Question 25

Zinc oxide is said to be amphoteric because it

• A. forms an acid salt
• B. is an insoluble base
• C. forms a double salt
• D. reacts with a base or an acidCorrect

Explanation

Amphoteric oxides are the oxides of metals that can react with both acids and bases. Examples are Al2O3 and ZnO.

Chemistry 2014 Objective — Question 26

Given the pH values: Lime 2.4, Banana 4.6, Distilled water 7.0, Milk of magnesia 10.5. Which of the following substances with the corresponding pH value is an alkali?

• A. Lime (2.4)
• B. Banana (4.6)
• C. Distilled water (7.0)
• D. Milk of magnesia (10.5)Correct

Explanation

A pH value less than 7 indicates acidity. The one greater than 7 indicates alkalinity. A pH value of 7 indicates neutrality. Milk of magnesia (pH 10.5) is the alkali.

Chemistry 2014 Objective — Question 27

The gases produced when Cu(NO₃)₂(s) was heated are

• A. NO and NO₂
• B. O₂ and NO₂Correct
• C. O₂ and NO
• D. NO₂ and N₂O₄

Explanation

When Cu(NO3)2 is heated, the gases produced are NO2 and O2: 2Cu(NO3)2 → 2CuO + 4NO2 + O2.

Chemistry 2014 Objective — Question 28

Which of the following salts on hydrolysis would give an alkaline solution?

• A. NH₄Cl
• B. AlCl₃
• C. CH₃COONaCorrect
• D. NH₄NO₃

Explanation

A salt from a strong base and a weak acid will be alkaline. CH3COONa is from a strong base (NaOH) and a weak acid (CH3COOH), so its solution will be alkaline.

Chemistry 2014 Objective — Question 29

Na₂CO₃(aq) + 2HCl(aq) → 2NaCl(aq)+H₂O(l)+CO₂(g). What volume of 0.02 moldm⁻³ Na₂CO₃(aq) would be required to completely neutralize 40 cm³ of 0.10 moldm⁻³ HCl(aq)?

• A. 200 cm³
• B. 100 cm³Correct
• C. 40 cm³
• D. 20 cm³

Explanation

Using CaVa/na = CbVb/nb with Ca=0.10, Va=40, Cb=0.02, na=2, nb=1: (0.10×40)/2 = (0.02×Vb)/1, so 0.04Vb=4, Vb=100cm³.

Chemistry 2014 Objective — Question 30

In which of the following experimental set-ups would the rate of evolution of hydrogen gas be fastest?

• A. Mg + HCl
• B. Fe + HCl
• C. Zn + HCl
• D. Ca + HClCorrect

Explanation

The question indirectly demands the most reactive of the metals given. Based on the reactivity series (K,Na,Ca,Mg,Al,Zn,Fe,Sn,Pb,H,Cu — decreasing reactivity), calcium is the most reactive metal given, so its reaction with HCl produces hydrogen gas fastest.

Chemistry 2014 Objective — Question 31

Which of the following factors would affect the equilibrium constant?

• A. Concentration
• B. TemperatureCorrect
• C. Pressure
• D. Volume

Explanation

Only temperature affects the equilibrium constant; concentration, pressure, and volume changes shift the equilibrium position but do not change the equilibrium constant itself.

Chemistry 2014 Objective — Question 32

Consider the following energy profile diagram of exothermic reaction. The enthalpy change, ΔH is

• A. +40 kJmol⁻¹
• B. −40 kJmol⁻¹Correct
• C. +80 kJmol⁻¹
• D. −80 kJmol⁻¹

Explanation

From the diagram, reactants are at about 80 kJ/mol and products at about 40 kJ/mol. Since the reaction is exothermic (energy released), ΔH = products − reactants = 40−80 = −40 kJmol⁻¹.

Chemistry 2014 Objective — Question 33

N₂+3H₂ ⇌ 2NH₃, ΔH=−x kJ mol⁻¹. Which of the following conditions would increase the yield of NH₃?

• A. Addition of iron catalyst
• B. Increase in the temperature of the system
• C. Increase in the volume occupied by reactants
• D. Increase in the total pressure of the systemCorrect

Explanation

Since the forward reaction is exothermic and results in fewer gas molecules, increasing the total pressure of the system favours the forward reaction, increasing the yield of NH3.

Chemistry 2014 Objective — Question 34

What is the function of manganese (IV) oxide in the reaction represented by the following equation? MnO₂+4HCl→MnCl₂+2H₂O+Cl₂

• A. Catalyst
• B. Dehydrating agent
• C. Oxidizing agentCorrect
• D. Reducing agent

Explanation

Fluorine (the most electronegative element known) is the most reactive halogen; in this reaction, MnO2 acts as an oxidizing agent, being reduced from +4 to +2 while oxidizing Cl⁻ to Cl2.

Chemistry 2014 Objective — Question 35

The reaction that occurs at the anode when CuSO₄(aq) is electrolyzed using carbon electrode is

• A. 2H⁺(aq)+2e⁻→H₂(g)
• B. Cu²⁺(aq)+2e⁻→Cu(s)
• C. 4OH⁻+4e⁻→2H₂O(l)+O₂(g)Correct
• D. SO₄²⁻(aq)−2e⁻→SO₂(g)+O₂(g)

Explanation

At the anode (oxidation), hydroxide ions are discharged in preference to sulphate ions: 4OH⁻ → 2H2O + O2 + 4e⁻.

Chemistry 2014 Objective — Question 36

Reduction is the process of

• A. loss of electron
• B. loss of hydrogen
• C. loss of oxygenCorrect
• D. addition of electronegative elements

Explanation

Reduction is the process of loss of oxygen (or gain of electrons/hydrogen).

Chemistry 2014 Objective — Question 37

Ethene molecules can be added to one another to form a long chain compound called a

• A. dimer
• B. monomer
• C. polymerCorrect
• D. trimer

Explanation

When many ethene (monomer) molecules join together to form a long chain, the resulting compound is called a polymer; this process is polymerization.

Chemistry 2014 Objective — Question 38

Which of the following compounds determines the octane rating of petrol?

• A. 1,2,3-trimethyl pentane
• B. 2,3,5-trimethyl octane
• C. 2,3,5-trimethyl pentane
• D. 2,2,4-trimethyl pentaneCorrect

Explanation

2,2,4-trimethylpentane (isooctane) is the reference compound used to determine the octane rating of petrol.

Chemistry 2014 Objective — Question 39

Which type of reaction is illustrated by the following equation? C₁₂H₂₆→5C₂H₄+C₂H₆

• A. Addition
• B. CrackingCorrect
• C. Hydrogenation
• D. Polymerization

Explanation

The breaking down of a large hydrocarbon molecule (C12H26) into smaller molecules is cracking.

Chemistry 2014 Objective — Question 40

The IUPAC name of the following organic compound HOOC-COOH is

• A. ethan-1,2-dioic acidCorrect
• B. ethanoic acid
• C. oxalic acid
• D. propan-1,2-dioic acid

Explanation

HOOC-COOH is a two-carbon dicarboxylic acid, named ethan-1,2-dioic acid (also commonly known as oxalic acid).

Chemistry 2014 Objective — Question 41

The enzyme that catalyses the conversion of glucose to ethanol and carbon (IV) oxide is

• A. diastase
• B. maltase
• C. ptyalin
• D. zymaseCorrect

Explanation

Zymase is the enzyme that catalyses the fermentation of glucose to ethanol and carbon(IV) oxide.

Chemistry 2014 Objective — Question 42

A colourless hydrocarbon with a sweet smell undergoes substitution reaction. The hydrocarbon is likely to be a(n)

• A. alkanol
• B. benzeneCorrect
• C. ester
• D. methane

Explanation

Benzene is a colourless hydrocarbon with a characteristic sweet smell that primarily undergoes substitution reactions.

Chemistry 2014 Objective — Question 43

C₂H₄+3O₂(g)→2CO₂(g)+2H₂O(l). How many moles of ethene would be burnt to produce 0.1 mole of water?

• A. 0.05 moleCorrect
• B. 0.10 mole
• C. 0.20 mole
• D. 2.00 moles

Explanation

From the equation, 1 mole C2H4 produces 2 moles H2O. So to produce 0.1 mole H2O, moles of C2H4 = 0.1/2 = 0.05 mole.

Chemistry 2014 Objective — Question 44

The liquid hydrocarbon likely to be found in the fraction of crude oil used for domestic cooking is

• A. C₃H₈
• B. C₅H₁₂Correct
• C. C₁₃H₂₈
• D. C₂₀H₄₂

Explanation

C5H12 falls in the fraction range (light liquid hydrocarbons) associated with domestic cooking fuel (LPG/naphtha range).

Chemistry 2014 Objective — Question 45

The mass of 800cm³ of a compound with empirical formula CH₂O and relative molecular mass would be...

• A. Ethanal
• B. Ethane
• C. Ethanol
• D. Ethanoic acidCorrect

Explanation

With empirical formula CH2O and RMM corresponding to a dimer (C2H4O2), the compound is ethanoic acid, CH3COOH.

Chemistry 2014 Objective — Question 46

The production of biogas from the fermentation of waste materials is an example of

• A. combustion
• B. biochemical incineration
• C. refining
• D. recyclingCorrect

Explanation

The production of biogas from fermentation of waste materials is an example of recycling of waste material into useful energy.

Chemistry 2014 Objective — Question 47

The purity of a solid sample can best be determined by its

• A. boiling point
• B. melting pointCorrect
• C. conductivity
• D. solubility

Explanation

The purity of a solid sample can best be determined by its melting point — a pure solid has a sharp, well-defined melting point.

Chemistry 2014 Objective — Question 48

Which of the following gases is used to retard the vapourization of the filament in a light bulb?

• A. ArgonCorrect
• B. Helium
• C. Hydrogen
• D. Oxygen

Explanation

Argon gas is used to retard vapourization of the tungsten filament in a light bulb, being an inert gas.

Chemistry 2014 Objective — Question 49

The most common process in the extraction of metals from their ore is

• A. catalysis
• B. electrolysis
• C. oxidation
• D. reductionCorrect

Explanation

The most common process in the extraction of metals from their ores is reduction (of the metal oxide/compound to the free metal).

Chemistry 2014 Objective — Question 50

The oxide from electric power station is

• A. carbon (IV) oxide
• B. copper (II) oxide
• C. nitrogen (IV) oxide
• D. sulphur (IV) oxideCorrect

Explanation

Electric power stations that burn fossil fuels containing sulphur produce sulphur (IV) oxide as a major pollutant oxide.