WAEC Chemistry Questions and Answers 2020/2021 Objectives/ESSAY Download PDF

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2020 WAEC Chemistry Examination Questions and Answers

The resources below on WAEC Chemistry Questions & Answers 2020/2021 to OBJ/ESSAY have been provided by West African Examination Council (WAEC) to assist you to understand the required standards expected in Chemistry final 2020 Examination.

WAEC Chemistry Questions & Answers 2019/2020 to OBJ/ESSAY

The 2020 WAEC on chemistry will be divided into 3 papers of which must be taken. Papers 1 and 2 will be a composite paper to be taken at the same sitting.

WAEC Chemistry Objectives Questions and Answers 2020

PAPER 1 : Will consist of fifty multiple choice objective questions drawn from Section A of the syllabus. Candidates will be required to answer all the questions within 1 hour for 50 marks.

PAPER 2 : Will be a 2-hour essay paper covering the entire syllabus and carrying a maximum of 100 marks. The paper will be in two sections:

Below is WAEC Chemistry sample past Questions & Answers 2020/2021 to OBJ/ESSAY

PAPER 1 (OBJECTIVE TEST)

1. Copper metal will react with concentrated trioxonitrate (V) acid to give?

  • A. Cu(NO3)3 + NO + N2O4 + H2O
  • B. Cu(NO3)2 + NO + H2O
  • C. CuO + NO2 + H2O
  • D. Cu(NO2)3 + NO2 + H2O

ANSWER: D (Cu(NO2)3 + NO2 + H2O)

2. Equilibrium is said to be attained in reversible reaction when

  • A. all the reactants have been used up
  • B. all the products have been formed
  • C. there is no further change in temperature
  • D. the rates of the forward and backward reactions are equal
  • E. the rate of formation of the products decreases with time

ANSWER: D (the rates of the forward and backward reactions are equal)

3/ An acid present in proteins is

  • A. lactic acid
  • B. amino acid
  • C. propanoic acid
  • D. palmitic acid
  • E. stearic acid

ANSWER: B

4. The following are uses of sulphur except

  • A. manufacture of tetraoxosulphate (VI) acid
  • B. prevention of the growth of fungi
  • C. vulcanization rubber
  • D. manufacture of dyes
  • E. coating of steel to prevent rusting

ANSWER: B (prevention of the growth of fungi)

5. The reaction represented by the equation NaOH(aq) + HCI(aq) → NaCI(aq) + H2O(/)

  • A. is a double decomposition
  • B. is a neutralization
  • C. is reversible
  • D. is usually catalysed
  • E. attains equilibrium after a few seconds

ANSWER: B (is a neutralization)

6. Which of the following compound is aromatic?

  • A. Benzene
  • B. Cyclobutane
  • C. Cyclopentane
  • D. Hexane
  • E. Ethene

ANSWER: A (Benzene)

7. Which of the following does not affect the rate of a chemical reaction?

  • A. Addition or presence of a catalyst
  • B. Size of the reacting particles
  • C. The enthalpy change for the reaction
  • D. Concentration of the reactants
  • E. Temperatureat which the reaction is carried out

ANSWER: C (The enthalpy change for the reaction)

9. Given that 32.0g sulphur contains 6.02 x 10 23 sulphur atoms how many atoms are there in 2.70g of aluminium? {Al = 27, S =32}

  • A. 6.02 x 10 23
  • B. 3.01 x 1022
  • C. 6.02 x 1022
  • D. 5. 08 x 1022
  • E. 3.01 x 1022

ANSWER: C ( 6.02 x 1022 )

Check Explanation

27g Aluminium = 6.02×10236.02×1023

1g Al = 6.02×1023276.02×102327

2.7g Al = 6.02×102327×2.76.02×102327×2.7

= 6.02×1022Al6.02×1022Al atoms

WAEC Chemistry Practice Questions

1.The minimum amount of energy required for effective collisions between reacting particles is known

A) Activation energy
B) Bond energy
C) Kinetic energy
D) Potential energy

2.The bond formed between H2OH2O and H+H+ to form the hydroxonium H3O+H3O+ is

A) Dative

B) Covalent

C) Electrovalent

D) IonicAn element XX forms the following oxides X2O,XOX2O,XO and XO2.XO2. This phenomenon illustrates the law of ________.

A) Conservation of mass

B) Definite proportion

C) Mass action

D) Multiple proportion

4.. How many moles of oxygen would contain 1.204×10241.204×1024 molecules?
NB: Avogadro’s constant (NA) =6.02×1023=6.02×1023

A) 1
B) 2
C) 3
D) 4

Which of the following statements about solids is correct?

A) Solid particles are less orderly than those of a liquid

B) Solid have lower densities than liquids

C) Solid particles have greater kinetic energies than those of liquids

D) Solid particles cannot be easily compressed

Which of the following apparatus can be used to measure a specific volume of a liquid accurately?

A) Beaker

B) Conical flask

C) Measuring cyclinder

D) PipetteThe general gas equation PVT=KPVT=K is a combination of

A) Boyle’s and Charles’ laws

B) Boyle’s and Graham’s laws

C) Charles’ and Graham’s laws

D) Dalton’s and Graham’s lawsThe spreading of the scent of a flower in a garden is an example of?

A) Brownian motion

B) Diffusion

C) Osmosis

D) Tynadal effect

Propane and carbon (IV) oxide diffuse at the same rate because [H = 1.00, C = 12.0, O = 16.0]

Options

A) They are both gases

B) Their molecules contain carbon

C) They have the same relative molecular mass

D) Both are denser than air

1O. The energy which accompanies the addition of an electron to an isolated gaseous atom isA) Atomization

B) Electronegativity

C) Electron affinity

D) Ionization

  1. A sample of hard water contains some calcium sulphate and calcium hydrogen carbonate. The total hardness may therefore be removed by
  2. boiling the water
  3. adding excess calcium hydroxide
  4. adding a calculated amount of calcium hydroxide
  5. adding sodium carbonate
  6. adding magnesium hydroxide
  1. During the electrolysis of copper II sulphate between platinum electrodes, if litmus solution is added to the anode compartment,
  2. the litmus turns blue but no gas is evolved
  3. the litmus turns blue and oxygen is evolved
  4. the litmus turns blue and hydrogen is evolved
  5. the litmus turns red and oxygen is evolved
  6. the litmus turns red and then becomes colourless
  1. The reaction between an organic acid and an alcohol in the presence of an acid catalyst is known as;
  2. saponification
  3. dehydration
  4. esterification
  5. hydrolysis
  6. hydration
  1. The IUPAC names of the compounds CH3COOH and CH2=CH2 are respectively;
  2. acetic acid and ethane
  3. ethanoic acid and ethene
  4. methanoic acid and ethylene
  5. ethanol and ethene
  6. acetic acid and ethylene
  1. If 30cm3 of oxygen diffuses through a porous pot in 7 seconds, how long will it take 60cm3 of chlorine to diffuse through the same pot, if the vapour densities of oxygen and chlorine are 16 and 36 respectively?
  2. 9.3 sec
  3. 14 sec
  4. 21 sec
  5. 28 sec
  6. 30.3 sec
  1. When heat is absorbed during a chemical reaction, the reaction is said to be
  2. thermodynamic
  3. exothermic
  4. isothermal
  5. endothermic
  6. thermostatic
  1. When large hydrocarbon molecules are heated at high temperature in the presence of a catalyst to give smaller molecules, the process is known as
  2. disintegration
  3. polymerization
  4. cracking
  5. degradation
  6. distillation
  1. The pH of four solutions W, X, Y, Z are 4, 6, 8, 10 respectively, therefore
  2. none of these solutions is acidic
  3. the pH of Y is made more acidic by addition of distilled water
  4. Z is the most acidic solution
  5. W is the most acidic solution
  6. X is neutral
  1. When each of the nitrates of Potassium, Magnesium and iron is heated,
  2. all the nitrates decompose to their oxides
  3. the nitrate of magnesium gives the nitrite and oxygen
  4. the nitrates of iron magnesium and iron give the oxides
  5. the nitrate of iron gives the nitrite and oxygen
  6. the nitrate of the magnesium is not decomposed

2O. Which of the following metals cannot replace hydrogen from water or steam?

  1. Sodium
  2. Magnesium
  3. Iron
  4. Calcium
  5. Copper
  1. small quantity of solid ammonium chloride (NH4Cl) was heated gently in a test tube, the solid gradually disappears to produce two gases. Later, a white cloudy deposit was observed on the cooler part of the test tube. The ammonium chloride is said to have undergone
  2. distillation
  3. sublimation
  4. precipitation
  5. evaporation
  6. decomposition
  1. Elements P, Q, R, S have 6, 11, 15, 17 electrons respectively, therefore,
  2. P will form an electrovalent bond with R
  3. Q will form a covalent bond with S
  4. R will form an electrovalent bond with S
  5. Q will form an electrovalent bond with S
  6. Q will form a covalent bond with R
  1. An element X forms the following compounds with chlorine; XCl4, XCl3, XCl2. This illustrates the
  2. law of multiple proportions
  3. law of chemical proportions
  4. law of simple proportions
  5. law of conservation of mass
  6. law of definite proportions
  1. The oxidation state of chlorine in potassium chlorate is
  2. +1
  3. +2
  4. +3
  5. +5
  6. +7
  1. 10 When air which contains the gases Oxygen, nitrogen, carbondioxide, water vapour and the rare gases, is passed through alkaline pyrogallol and then over quicklime, the only gases left are;
  2. nitrogen and carbondioxide
  3. the rare gases
  4. nitrogen and oxygen
  5. nitrogen and the rare gases
  6. nitrogen, carbondioxide and the rare
  1. Which of the following statements is NOT correct?
  2. The average kinetic energy of a gas is directly proportional to its temperature
  3. At constant tempearture, the volume of a gas increases as the pressure increases
  4. The pressure of a gas is inversely proportional to its volume
  5. The temperature of a gas is directly proportional to its volume
  6. The collisions of molecules with each other are inelastic
  1. Zinc Oxide is a
  2. Basic Oxide
  3. Acidic Oxide
  4. Amphoteric Oxide
  5. Neutral Oxide
  6. Reactive Oxide
  1. When sodium chloride and metallic sodium are each dissolved in water
  2. both processes are exothermic
  3. both processes are endothermic
  4. the dissolution of metallic sodium is endothermic
  5. the dissolution of metallic sodium is exothermic
  6. the dissolution of sodium chloride is explosive
  1. The periodic classification of elements is an arrangement of the elements in order of their
  2. Atomic Weights
  3. Isotopic Weights
  4. Molecular Weights
  5. Atomic Numbers
  6. Atomic Masses

3O. In the reaction between sodium hydroxide and sulphuric acid solutions, what volume of 0.5 molar sodium hydroxide would exactly neutralise 10cm3 of 1.25 molar sulphuric acid?

  1. 5cm3
  2. 10cm3
  3. 20cm3
  4. 25cm3
  5. 50cm3
  1. An aqueous solution of (NH4)2SO4is
  2. A) Acidic
  3. B) Alkaline
  4. C) Amphoteric
  5. D) Neutral
  1. When NH4Cl(s)is dissolved in water, the container feels cold to touch. This implies……
  2. A) The process is endothermic
  3. B) The process is exothermic
  4. C) NH4Cl forms a saturated solution
  5. D) NH4Cl is highly soluble in water
  1. The pH of four solutions M, N, Q and R are 2, 6, 8 and 11 respectively.
    Which of the following deductions about the solutions is correct?
  2. A) The pH of N is increased when the solution is diluted
  3. B) The pH of Q is increased when the solution is evaporated
  4. C) M is the most alkaline solution
  5. D) R is the most acidic solution
  1. Consider the following reaction equation
    H3O+(aq)+ OH(aq)→ 2H2O(l)
    The reaction represents
  2. A) Esterification
  3. B) Hydrolysis
  4. C) Neutralization
  5. D) Redox
  1. The refreshing characteristic taste of fizzy drinks is due to the presence of
  2. A) Carbon (IV) oxide
  3. B) Glucose
  4. C) Hydrogen
  5. D) Sodium Citrate
  1. Chemical equilibrium is attained when
  2. A) All the reactants have been completely used up
  3. B) The reaction goes to completion
  4. C) The concentration of reactants and products remain constant
  5. D) The concentration of reactants and products are equal
  1. Which of the following factors will affect the rate of the reaction represented by the following equation?
    2HCl(aq)+ CaCO3(s)→ CaCl2(aq) + H2O(l) + CO2(g)
  2. Pressure
    II. Concentration
    III. Nature of reactants
    IV. Temperature
  3. A) I and II only
  4. B) II, III and IV only
  5. C) I, II and III only
  6. D) I, II, III and IV
  7. On evaporation to dryness, 350cm33of saturated solution of salt Z gave 55.5g of salt. What is the solubility of the salt? [Z = 101]
  8. A) 1.57 moldm-3
  9. B) 3.14 moldm-3
  10. C) 6.28 moldm-3
  11. D) 12.56 moldm-3

39.Which of the following salts when dissolved in water will form a solution that will change blue litmus to red?

  1. A) CH3COONa
  2. B) NH4Cl
  3. C) NaCl
  4. D) KCl

4O. Which of the following bonds are broken when ethanol is boiled?

  1. Covalent bonds
    II. Ionic bonds
    III. Hydrogen bonds
  2. A) I only
  3. B) II only
  4. C) III only
  5. D) I, II, III
  1. A compound with molecular formula CH2O2is
  2. A) A Carbohydrate
  3. B) A Carboxylic acid
  4. C) An alkanol
  5. D) An ester
  1. The quantity of electricity required to discharge 1 mole of univalent ion is
  2. A) 9600 C
  3. B) 48250 C
  4. C) 96500 C
  5. D) 193000 C
  1. Chlorine water is used as a bleaching agent because it is
  2. A) An acidic solution
  3. B) An alkaline solution
  4. C) An oxidizing agent
  5. D) A reducing agen

44.Which of the following substances is a non-electrolyte?

  1. A) H2SO4
  2. B) CH3COOH
  3. C) C6H12O6
  4. D) NH4Cl

45.The oxidation number of sulphur is +4 in

  1. A) Na2S2O3
  2. B) H2SO3
  3. C) H2SO4
  4. D) SO3

46.Consider the following ionic equation:
Cr2O72-+ 14H++ ne → 2Cr3+ + 7H2O.
The value of n in the equation is _______?

  1. A) 7
  2. B) 6
  3. C) 3
  4. D) 2

47.Consider the following half-cell reactions.
Al(s)→ Al3+(aq)+ 3e
Cu2+(aq) + 2e → Cu(s)

48.The overall equation for the reaction is

  1. A) Al(s)+ Cu2+(aq)→ Al3+(aq) + Cu(s)
  2. B) 2Al(s)+ Cu2+(aq)→ 2Al(aq) + Cu(s)
  3. C) 2Al(s)+ 3Cu2+(aq)→ 3Cu(s) + 2Al3+(aq)
  4. D) 3Al(s)+ 2Cu2+(aq)→ Cu(s) + 3Al3+(aq)

49.Amino acids are obtained from proteins by

  1. A) Hydrolysis
  2. B) Oxidation
  3. C) Polymerization
  4. D) Reductio

5O. When a compound X is heated with concentrated tetraoxosulphate (VI) acid, it produces an alkene. X is an

  1. A) Alkane
  2. B) Alkanol
  3. C) Alkanoate
  4. D) Alkyne
  1. Ripening of fruits is hastened by using
  2. A) Ethanol
  3. B) Ethane
  4. C) Ethene
  5. D) Ethyne
  1. The compound that makes palm wine taste sour after exposure to the air for few days is
  2. A) Ethanol
  3. B) Ethanoic acid
  4. C) Methanol
  5. D) Methanoic acid
  1. Which of the following compounds is/are secondary alkanols?
  2. i) CH3CH(CH3)CH3OH
    ii) CH3CH2CH(OH)CH3
    iii) CH3C(OH)(CH3)CH3
  1. A) I only
  2. B) II only
  3. C) I and III only
  4. D) II and III only
  5. Consider the following reaction equation:
    C2H4(g)+ 3O2(g)→ 2CO2(g) + 2H2O(l).

The volume of oxygen at s.t.p that will be required to burn 14g of ethene is
[C2H4 = 28; Molar volume of gas at s.t.p = 22.4dm3]

  1. A) 64.2dm3
  2. B) 33.6dm3
  3. C) 11.2dm3
  4. D) 3.73dm3
  1. Which of the following sources of energy contributes to green-house effect?
  2. A) Natural gas
  3. B) Nuclear
  4. C) Wind
  5. D) Solar
  1. A consequence of global warming is
  2. A) Air pollution
  3. B) Flooding
  4. C) Increased humidity
  5. D) Water pollution
  1. Which of the following metals is common to both brass and bronze?
  2. A) Aluminium
  3. B) Copper
  4. C) Lead
  5. D) Iron
  1. The alkanol obtained from the production of soap is
  2. A) Dihydric Alkanol
  3. B) Tertiary Alkanol
  4. C) Trihydric Alkanol
  5. D) Monohydric Alkanol
  1. The negatively charged particle in an atom is the
  2. A) Electron
  3. B) Neutron
  4. C) Positron
  5. D) Proton

6O. How many orbits are contained in an atom with atomic number 13?

  1. A) 7
  2. B) 6
  3. C) 5
  4. D) 3
  5. The Van der Waals forces are dominant intermolecular forces in __________.
  6. A) Ammonium chloride
  7. B) Chlorine
  8. C) Sodium chloride
  9. D) Wate

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Getting WAEC 2020 Chemistry Essay Answers

  1. (a) (i) What is the structure of the atom as proposed by Rutherford?
    (ii) Distinguish between the atomic number and the mass number of an element.
    (iii) Explain briefly why the relative atomic mass of chlorine is not a whole number.

(b) (i) What is meant by first ionization energy?
(ii) List three properties of electrovalent compounds
(iii) Consider the following pairs of elements:
9F and 17CL;
12Mg and 20Ca.
Explain briefly why the elements in each pair have similar chemical properties.

(c) Explain briefly the following terms using an appropriate example in each case
(i) homologous series;
(ii) heterolytic fission.

(d) State the indicator(s) which could be used to determine the end-point of the following titrations:
(i) dilute hydrochloric acid against sodium hydroxide solution;
(ii) dilute hydrochloric acid against ammonium hydroxide solution;
(iii) ethanoic acid against sodium hydroxide solution.

(e) A solid chloride E which sublimed on heating reacted with an alkali F to give a choking gas G. G turned moist red litmus paper blue. Identify E,F and G.

ANS: (a) (i) The atom has small/ tiny positively charged centre /nucleus with electrons surrounding the space around the centre.
(ii) Atomic number of an element is the number of protons/electrons in an atom of the element while mass number is the sum of the protons and neutrons in the atom of the element.
(iii) Chlorine atom is made up of a mixture of isotopes and the relative atomic mass of chlorine is the average of its isotopic masses.

(b) (i) Is the (minimum) energy required to remove one mole of an electron from one mole of gaseous atom (to form one mole gaseous charged ion
(ii) High melting /boiling point;
Ability to conduct electricity in the molten state or in solution;
Solid at room temperature;
Soluble in water or polar solvents /insoluble in non-polar solvents.
(iii) Atoms of the elements in each pair have the same number of electrons in their outer-most shell therefore similar chemical properties.

(c) (i) Is a family of organic compounds:
– where successive members differ by –CH2 of molar mass of 14;
– with similar chemical properties;
– which conform to the same general formula;
– which show gradation of physical properties;
– which have the same general method of preparation. e.g alkanes, alkenes , alkanols.
(ii) Is a process in which a (covalent) bond is broken in such a way that the electron pair is completely transferred to one of the atoms (resulting in the formation of ions)
H ÷ CI → H+ + Cl-/ HCl ® H+ + Cl-
(d)(i) Methyl orange/ methyl red/ phenolphthalein;
(ii) Methyl orange/ methyl red;
(iii) Phenolphthalein.
(e) E – NH4Cl
F – NaOH, KOH, or Ca (OH)2, Li OH, CsOH, Ba(oH)2, Mg(OH)2
G – NH3.

  1. (a) (i) Define saturated solution.
    (ii) The solubility of KN03 at 20°C was 3.00 mol dm-3 If 67.0g of KN03 was added to 250cm3 of water and stirred at 20°C, determine whether the solution formed was saturated or not at that temperature.

(b) (i) Distinguish between dative bond and covalent bond.
(ii) Explain why sugar and common salt do not conduct electricity in the solid state.
(iii) State the type of intermolecular forces present in
I. hydrogen fluoride;
II. argon.
(iv) Consider the compounds with the following structures:
S – H —-N and 0 – H —–N
In which of the compounds is the hydrogen bond stronger? Give reason for your answer.

(c) (i) State Dalton’s Law of Partial Pressure.
(ii) If 200cm3 of carbon(IV) oxide were collected over water at 18°C and 700 mmHg, determine the volume of the dry gas at s.t.p.[ standard vapour pressure of water at 18°C = 15 mmHg]

ANS: (a) (i) Is a solution which contains the maximum amount of solute it can dissolve at a given temperature (in the presence of undissolved solute).
(ii) Solubility of KN03 in in g dm-3 = 3.00 x 101 = 303
.. 1000cm3 of saturated solution = 303g
250cm3 of the solution = 303 x 250
1000
= 75.8 g
Since the quantity of KN03 added (67.0) to 250 cnr’ of water is less than maximum amount required to form a saturated solution, then the solution is unsaturated.

(b)(i) In dative bond, only one of the participating atoms/ species donated electrons to be shared by both atoms while in covalent bond both participating atoms/ species contribute equally the electrons being shared.
(ii) Sugar is covalent while common salt (NaCl) is electrovalent/ ionic. Electrical conductivity (in compounds) depends on presence of mobile ions.
(iii) The intermolecular forces present in hydrogen fluoride and argon were hydrogen bond and van der Waal’s forces respectively.
(iv) 0 – H —- N has the stronger hydrogen bond because oxygen is more electronegative and smaller in size than sulphur.

(c)(i) the total pressure exerted by a mixture of gases which do not react chemically is equal to the sum of the individual partial pressures of the gases in the mixture.
(ii) pressure of the dry gas (P 1) = 700 – 15 = 685 mmHg
VI = 200cm3, TI = 18°C = 273 + 18 = 291K, P2 = 760 mmHg,
T2 = 273
P1V1 = P2V2
T1 T2
V2 = P1V1T2 =
P2T1

= 685 x 200 x 273
760 x 291

= 169.1cm3

  1. (a) (i) Define nuclear fission
    (ii) A certain natural decay series starts with and ends with. Each step involves the loss of an alpha or a beta particle. Using the given information, deduce how many alpha and beta particles were emitted.
    (b) Consider the equilibrium reaction represented by the following equation: A2(g) + 3B2(g) 2AB3(g); H = + kJmol-1
    Explain briefly the effect of each of the following changes on the equilibrium composition;
    (i) increase in concentration of B;
    (ii) decrease in pressure of the system;
    (iii) addition of catalyst.

Those were Our WAEC Chemistry Questions & Answers 2020/2021 to OBJ/ESSAY and there were all sourced from the right place and there is an alignment with the 2020  waec questions and answers on Chemistry and that’s why we can say that the questions for this year’s WAEC Chemistry exams is drawn from the previous year’s questions. Well, that was all I can contribute to your waec  chemistry exams success. Hope this was helpful? Those were some of the 2020 waec chemistry questions and answers for 2020 waec exam.

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