MAY/JUNE 2020 WASSCE Chemistry 1 & 2 (Objective and Theory): Complete Question and Answer Guide for SHS Students
Introduction
Preparing for the West African Senior School Certificate Examination (WASSCE) Chemistry 1 Theory paper requires not only understanding key concepts but also familiarizing yourself with the types of questions commonly asked. The 2020 WASSCE May-June Chemistry 1 exam covered a wide range of essential chemistry topics—from chemical reactions and atomic structure to hydrocarbons and equilibrium principles. This comprehensive question-and-answer guide breaks down all 50 multiple-choice questions from that exam, providing clear and concise answers to help you build confidence and deepen your understanding. Whether you’re a student aiming for top grades or a teacher looking for a reliable revision resource, this guide offers the clarity and authority you need to excel in chemistry.
WASSCE MAY/JUNE 2020 – CHEMISTRY 1 OBJECTIVES
1. Which of the following substances is an example of a fine chemical?
A. Sodium hydroxide
B. Water
C. Ethanol
D. Sand
Answer: A. Sodium hydroxide
2. The IUPAC name of the compound represented by the structure below is?
A. 2-chloro but-1,3-diene
B. 1-chloro but-2-ene
C. 1-chloro butane
D. 2-chloro butane
Answer: A. 2-chloro but-1,3-diene
3. Which of the following substances is a polypeptide?
A. Sugar
B. Starch
C. Protein
D. Cellulose
Answer: C. Protein
4. Which of the following products could be formed during incomplete combustion of a hydrocarbon?
A. Carbon dioxide and water
B. Carbon dioxide and carbon monoxide
C. Carbon and carbon monoxide
D. Carbon monoxide and water
Answer: C. Carbon and carbon monoxide
5. What quantity of electrons is lost when one mole of iron (II) ions is oxidized to iron (III)?
A. 2 moles
B. 1 mole
C. 3 moles
D. 0.5 moles
Answer: B. 1 mole
6. What is the mass of silver deposited when 24,125 C of electricity is passed through a solution of silver salt?
[Ag = 108, F = 96,500 C]
A. 108g
B. 54g
C. 27g
D. 216g
Answer: B. 54g
7. Equal masses of calcium trioxocarbonate (IV) were added to dilute hydrochloric acid at specified temperatures. Under which of the following conditions would the reaction be slowest?
A. Calcium trioxocarbonate (IV) chips at 20°C
B. Calcium trioxocarbonate (IV) powder at 40°C
C. Calcium trioxocarbonate (IV) chips at 60°C
D. Calcium trioxocarbonate (IV) powder at 20°C
Answer: A. Calcium trioxocarbonate (IV) chips at 20°C
8. The high solubility of ethanol in water is due to?
A. Covalent bonding
B. Ionic bonding
C. Van der Waals forces
D. Hydrogen bonding
Answer: D. Hydrogen bonding
9. Which of the following metals reacts slowly with cold water?
A. Sodium
B. Calcium
C. Iron
D. Potassium
Answer: C. Iron
10. Which of the following pairs of properties of alkali metals decreases down the group?
A. Atomic radius and melting point
B. Atomic radius and boiling point
C. First ionization energy and melting point
D. First ionization energy and atomic radius
Answer: C. First ionization energy and melting point
11. The most suitable process of obtaining water from an aqueous solution of sugar is
A. Distillation
B. Crystallization
C. Filtration
D. Evaporation
Answer: A. Distillation
12. Group VII elements in their combined states are called?
A. Halogens
B. Halides
C. Alkali metals
D. Noble gases
Answer: B. Halides
13. When an ionic bond is broken, bonding electrons are
A. Shared equally
B. Lost by the more electronegative atom
C. Gained by the most electronegative atom
D. Lost by the less electronegative atom
Answer: C. Gained by the most electronegative atom
14. The oxidation state of chlorine in NaClO₃ is?
A. +3
B. +4
C. +5
D. +6
Answer: C. +5
15. A balanced chemical equation is based on the law of?
A. Conservation of energy
B. Conservation of charge
C. Conservation of mass
D. Conservation of volume
Answer: C. Conservation of mass
16. Which of the following pairs of elements has the greatest difference in electronegativity?
A. Na and F
B. H and O
C. C and O
D. S and O
Answer: A. Na and F
17. A factor that is considered most important when siting a chemical industry is?
A. Availability of labor
B. Nearness to raw materials
C. Distance to market
D. Availability of capital
Answer: B. Nearness to raw materials
18. The boiling point of pentane is higher than that of propane because?
A. Pentane has stronger covalent bonds
B. Propane is more volatile
C. The intermolecular forces in pentane are stronger than those of propane
D. Propane has a higher molecular weight
Answer: C. The intermolecular forces in pentane are stronger than those of propane
19. Which of the following solids would not decompose on heating?
A. Lead (II) carbonate
B. Lead (I) trioxonitrate (V)
C. Sodium hydrogen carbonate
D. Calcium carbonate
Answer: B. Lead (I) trioxonitrate (V)
20. The following molecules have double covalent bonds between two atoms except?
A. O₂
B. C₂H₄
C. CO₂
D. Water
Answer: D. Water
21. The type of isomerism exhibited by cis and trans isomers is?
A. Structural
B. Geometrical
C. Optical
D. Functional group
Answer: B. Geometrical
22. Which of the following compounds has the lowest boiling point?
A. Butane (C₄H₁₀)
B. Propanol (C₃H₇OH)
C. Butanol (C₄H₉OH)
D. Propane (C₃H₈)
Answer: A. Butane (C₄H₁₀)
23. An alkanol containing 60% carbon by mass would have a molecular formula
A. C₃H₇OH
B. C₂H₅OH
C. CH₃OH
D. C₄H₉OH
Answer: B. C₂H₅OH
24. Which of the following compounds would release hydrogen when reacted with sodium metal?
A. CH₃COOH only
B. CH₃COOH and CH₃CH₂OH only
C. CH₃CH₂OH only
D. CH₃CH₂OH and C₆H₆ only
Answer: B. CH₃COOH and CH₃CH₂OH only
25. Which of the following substances is not a reducing agent?
A. Hydrogen
B. Carbon
C. Oxygen
D. Zinc
Answer: C. Oxygen
26. Which of the following statements is correct for a reaction at equilibrium?
A. Reactants are completely used up
B. Products are formed irreversibly
C. The rates of the forward and backward reactions are equal
D. The concentration of reactants is zero
Answer: C. The rates of the forward and backward reactions are equal
27. Which of the following reactions are always exothermic?
A. Neutralization only
B. Neutralization and Combustion
C. Combustion and Photosynthesis
D. Photosynthesis only
Answer: B. Neutralization and Combustion
28. Which of the following standard conditions is not correct about energy changes?
A. ΔH at 298 K is enthalpy change
B. Activation energy is required to start reaction
C. ΔH at 298 K is enthalpy of formation
D. ΔH at 298 K is the activation energy
Answer: D. ΔH at 298 K is the activation energy
29. If 5.0 cm³ of 0.200 mol/dm³ Na₂CO₃ was diluted to 250 cm³, what would be the concentration?
A. 0.004 mol/dm³
B. 0.010 mol/dm³
C. 0.020 mol/dm³
D. 0.400 mol/dm³
Answer: A. 0.004 mol/dm³
30. The initial volume and pressure of a given mass of gas is V and 3P. What is its pressure if its volume is increased to 2V at constant temperature?
A. 6P
B. 3P
C. 3/2 P
D. 2/3 P
Answer: D. 2/3 P
31. What volume of oxygen at s.t.p is required to burn completely 7.5 dm³ of methane?
Equation: CH₄ + 2O₂ → CO₂ + 2H₂O
A. 7.5 dm³
B. 15.0 dm³
C. 22.5 dm³
D. 30.0 dm³
Answer: B. 15.0 dm³
32. When 250 cm³ of saturated CuSO₄ solution was evaporated, 5.0 g salt was obtained. What is the solubility at 30°C? [CuSO₄ = 160]
A. 0.320 mol/dm³
B. 0.500 mol/dm³
C. 0.640 mol/dm³
D. 1.250 mol/dm³
Answer: C. 0.640 mol/dm³
33. The bond between NH₃ and H⁺ in NH₄⁺ is?
A. Dative
B. Ionic
C. Covalent
D. Hydrogen
Answer: A. Dative
34. Which of the following oxides has a giant covalent structure?
A. CO₂
B. NO₂
C. SO₂
D. SiO₂
Answer: D. SiO₂
35. Which of the following hydroxides is not readily soluble in water?
A. NaOH
B. Ca(OH)₂
C. KOH
D. Mg(OH)₂
Answer: B. Ca(OH)₂
36. Which of the following statements about solubility of a salt is correct?
A. Solubility decreases with temperature for all salts
B. Solubility is independent of temperature
C. Crystallization would be efficient for a salt whose solubility increases considerably with temperature
D. Crystallization is not affected by temperature
Answer: C. Crystallization would be efficient for a salt whose solubility increases considerably with temperature
37. How many moles of H₂SO₄ are there in 50 cm³ of 0.108 mol/dm³ solution?
A. 5.4 × 10⁻³ mol
B. 2.16 × 10⁻³ mol
C. 1.08 × 10⁻³ mol
D. 2.7 × 10⁻² mol
Answer: A. 5.4 × 10⁻³ mol
38. If 20 cm³ sodium hydroxide is neutralized by 20 cm³ of 0.01 mol/dm³ tetraoxosulphate(VI) acid, what is the concentration of the sodium hydroxide?
A. 0.010 mol/dm³
B. 0.005 mol/dm³
C. 0.020 mol/dm³
D. 0.002 mol/dm³
Answer: A. 0.010 mol/dm³
39. "Electrons always occupy the lowest empty energy level" is a statement of
A. Aufbau Principle
B. Pauli Exclusion Principle
C. Hund's Rule
D. Heisenberg's Uncertainty Principle
Answer: A. Aufbau Principle
40. Which of the following metals does not react with water to produce hydrogen?
A. Copper
B. Calcium
C. Sodium
D. Potassium
Answer: A. Copper
41. Which of the following arrangement of elements is in decreasing order of electronegativity?
A. Na, Mg, Al, Si, P
B. P, Si, Al, Mg, Na
C. Mg, Al, P, Si, Na
D. Si, P, Na, Mg, Al
Answer: B. P, Si, Al, Mg, Na
42. The metallic bond in magnesium is stronger than that in calcium because magnesium has a
A. higher atomic mass
B. smaller atomic size
C. larger atomic radius
D. lower ionization energy
Answer: B. smaller atomic size
43. Consider the reaction:
AgNO₃ + NaCl → AgCl + NaNO₃.
Steps to obtain pure dry AgCl:
A. Washing, filtration and drying
B. Filtration, washing and drying
C. Filtering, washing and drying
D. Evaporation, filtration and drying
Answer: C. Filtering, washing and drying
44. How many electrons does ³¹¹₁₅P³⁻ contain?
A. 12
B. 15
C. 18
D. 21
Answer: C. 18
45. The atomic number would equal mass number if the atom
A. contains protons and neutrons only
B. contains only neutrons
C. does not contain neutrons
D. contains electrons only
Answer: C. does not contain neutrons
46. Which process is not exhibited by atoms to attain more stable electron configuration?
A. Ionization
B. Hybridization of orbitals
C. Gain of electrons
D. Loss of electrons
Answer: B. Hybridization of orbitals
47. Which of the following quantities is a molar quantity?
A. Molarity
B. Molar mass
C. Relative atomic mass
D. Molecular mass
Answer: C Mass concentration
48. Dilution factor is the?
A. Volume of concentrated solution divided by volume of diluted solution
B. Volume of diluted solution divided by volume of concentrated solution
C. Number of times the volume of the concentrated solution is diluted
D. Volume of solvent added
Answer: C. Number of times the volume of the concentrated solution is diluted
49. Calcium chloride is an ionic compound. Which statements account for its ionic character?
I. Calcium has low ionization energy
II. Chlorine has high electron affinity
III. Chlorine has high ionization energy
IV. Calcium has high electronegativity
A. I and II only
B. II and III only
C. II, III and IV only
D. II, III and IV only
Answer: C. II, III and IV only
50. An example of a biodegradable pollutant is?
A. Plastic waste
B. Sewage
C. Lead
D. Mercury
Answer: B. Sewage
WASSCE MAY/JUNE 2020 – CHEMISTRY 1 ANSWERS
- B Hydrochloric acid
- A 2-chloro but-1,3-diene
- C Protein
- C I and III only
- C 1 mole
- D 27g
- A Calcium trioxocarbonate (IV) chips at 20°C
- D Hydrogen bonding
- D First ionization energy and melting point
- A Calcium
- A Crystallization
- A Halogens
- B Gained by the most electropositive atom
- C +5
- D Conservation of mass
- A Na and F
- B Nearness to raw materials
- B Pentane has more covalent bonds to break
- C Potassium trioxocarbonate (IV)
- D Water
- B Geometrical
- D C2H5OH
- C C3H7OH
- B I and II only
- C O2
- C The rates of the forward and backward reactions are equal
- B I and III only
- D ΔH at 298 K is the activation energy
- A 0.004 mol dm⁻³
- C 3/2 P
- C 15.0 dm³
- B 0.125
- A Dative
- D SiO2
- B Ca(OH)2
- C Crystallization would be efficient in separating out a salt whose solubility increases considerably with temperature
- B 5.4 × 10⁻³
- B 0.020
- A Aufbau Principle
- A Copper
- D P, Si, Al, Mg, Na
- B Smaller atomic size
- C Filtering, washing and drying
- D 18
- C Does not contain neutrons
- B Hybridization of orbitals
- C Mass concentration
- C Number of times the volume of the concentrated solution is diluted to give the dilute solution
- C II, III and IV only
- B Sewage
2020 WASSCE May/June Chemistry 2 Theory
Question 1
(a)(i) State Faraday's First Law of Electrolysis
Answer:
Faraday’s First Law of Electrolysis states that the mass of a substance deposited or liberated at an electrode during electrolysis is directly proportional to the quantity of electric charge passed through the electrolyte.
(a)(ii) Distinguish between a Strong Electrolyte and a Weak Electrolyte
Answer:
- Strong Electrolyte: Completely ionizes or dissociates in solution, producing a high concentration of ions (e.g., NaCl, HCl). Conducts electricity well.
- Weak Electrolyte: Partially ionizes in solution, producing fewer ions (e.g., acetic acid, ammonia). Conducts electricity poorly.
(b) State one chemical property of Ethyne
Answer:
Ethyne (acetylene) undergoes addition reactions due to its triple bond, such as addition of hydrogen to form ethene or ethane.
(c)(i) What is meant by the term Unsaturated Hydrocarbon?
Answer:
An unsaturated hydrocarbon is a hydrocarbon containing one or more double or triple bonds between carbon atoms, allowing it to undergo addition reactions.
(c)(ii) Complete the following reaction equation:
CH3 + CH3OH →
Answer:
This appears incomplete, but assuming it’s a radical reaction involving methyl radical (CH3·) and methanol (CH3OH), it would likely form an ether or a substituted compound. However, the exact product is unclear without more context.
(c)(iii) Name the major product formed in the cation stated in 1(c)(ii)
Answer:
Insufficient data to name the product specifically; generally, cationic intermediates form substitution or elimination products depending on reaction conditions.
(d) State one way by which the rate of esterification could be increased
Answer:
The rate of esterification can be increased by using a concentrated acid catalyst such as sulfuric acid or by removing the water produced to shift equilibrium.
(e) Calculate the number of molecules of hydrogen gas produced from 3.75g of Zinc reacting with excess sulfuric acid:
Zn + H2SO4 → ZnSO4 + H2
Given:
- Atomic mass Zn = 65.0 g/mol
- Avogadro’s number = 6.02 × 10²³ molecules/mol
Answer:
- Moles of Zn = mass / molar mass = 3.75 g / 65.0 g/mol = 0.0577 mol
- Reaction stoichiometry: 1 mole Zn produces 1 mole H₂ → moles of H₂ = 0.0577 mol
- Number of molecules = moles × Avogadro’s number = 0.0577 × 6.02 × 10²³ ≈ 3.47 × 10²² molecules
(f) State one effect of global warming
Answer:
One effect of global warming is the rise in global average temperatures, leading to climate changes such as melting ice caps and rising sea levels.
(g)(i) Which of the following equations represent redox processes?
Equations:
A. Pb(NO₃)₂ + H₂S → PbS + 2HNO₃
B. H₂ + C₂H₄ → C₂H₆
C. Zn(OH)₂ + 2OH⁻ → [Zn(OH)₄]²⁻
Answer:
- A and B represent redox processes.
- C is a complexation reaction, not redox.
(g)(ii) State the change in oxidation number of species that are oxidized or reduced
Answer:
- In equation A: Pb²⁺ remains +2; S changes from -2 in H₂S to -2 in PbS (no oxidation number change for Pb or S) → This is a precipitation, not redox.
- In equation B: H₂ (oxidation number 0) is oxidized to H⁺ (+1); C₂H₄ carbons reduced as the double bond is saturated → carbon reduction, hydrogen oxidation.
- More detailed analysis depends on reaction specifics.
(h)(i) State two main concepts of Bohr’s model of the atom
Answer:
- Electrons orbit the nucleus in fixed, quantized energy levels or shells without radiating energy.
- Electrons can jump between energy levels by absorbing or emitting photons of specific energies.
(h)(ii) State limitations of Bohr’s model
Answer:
- It only accurately describes hydrogen-like atoms (single electron).
- It doesn’t account for electron-electron interactions or explain atomic spectra of larger atoms.
(i) List three factors that could influence the equilibrium position of a reversible reaction
Answer:
- Concentration of reactants or products
- Temperature changes
- Pressure (for gaseous reactions)
(j) Calcium trioxocarbonate powder is added to equimolar solutions of hydrochloric acid and ethanoic acid. State one:
(i) Similarity in the observations in both reactions
(ii) Difference in the observations in both reactions
Answer:
(i) Both produce effervescence due to CO₂ gas release.
(ii) The reaction with HCl is faster and more vigorous than with ethanoic acid due to acid strength differences.
Conclusion
Mastering the topics tested in the 2020 WASSCE Chemistry 1 & 2 exam is a critical step towards achieving success in your final examinations. By thoroughly reviewing these questions and answers, you gain valuable insights into the fundamental principles of chemistry that underpin more advanced studies. Consistent practice using past exam questions like these enhances your problem-solving skills and builds exam confidence. Remember, understanding the reasoning behind each answer is just as important as memorizing facts. Use this guide as a springboard for further study and to identify areas where you may need additional focus. With dedication and smart revision strategies, you are well on your way to excelling in chemistry and beyond.