2020 WAEC Chemistry Answers, WAEC Chemistry questions and answers, WAEC Chemistry questions and everything you need to know about 2021 WAEC Chemistry Examination will be provided in this article. You will find Chemistry Paper 1 (Objective) and Chemistry 2 (Essay) here
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Below are the WAEC Chemistry questions. Read them and get ready to score high in your WAEC Chemistry exam.
The West Africa Examination Council (WAEC) is an examination body in Nigeria that conducts the Senior Secondary Certificate Examination and the General Certificate in Education in May/June and November/December respectively.
WAEC Chemistry Questions and Answers 2021
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(1a)
A molecular formula consists of the chemical symbols for the constituent followed by numeric subscripts showing the number of atoms of each element present while structural formula consists of symbols for the atoms connected by short lines that represent chemical bonds.
(1b)
(i) Screening effect
(ii) Size of atom
(iii) Nuclear change
(1c)
(i) The reaction must proceed both forward and backward i.e reversible
(ii) All the reactants and products are present at equilibrium
(1d)
(i) B
(ii) It has the least ionization energy among the three
(1e)
Graham’s law of diffusion states that the rate of diffusion of a gas is inversely proportional to the square root of their densities provided other conditions remained constant
(1f)
(i) Na2SO4, Mg(NO3)2
(ii) CaCO3
(1g)
(i) Protein – condensational polymer
(ii) Perspex – additional polymer
(iii) Nylon – Condensation polymer
(1h)
Atomic radius can be defined as the half distance between the nucleus of two covalently bonded atoms.
(1i)
Ethanol has a higher boiling point than propane because it has stronger force of attraction than propane which has a weak van der waal’s force.
(1j)
(i) It aids the digestion of food
(ii) It aids the action of enzymes
(iii) It controls the availablity of nutrients
The questions below are the WAEC Chemistry Questions. Go through them and be ready to score high in your WAEC 2021 Chemistry Examination.
1. What condition favours the formation of the product for the endothermic reaction, N2O4(g) —><—– 2NO2(g)
A. Decrease in pressure
B. A decrease in volume
C. An increase in pressure
D. A constant volume
ANSWER: A ( Decrease in pressure)
2. How many alkoxy alkanes can be obtained from the molecular formula C4 H4O4
A. 1
B. 2
C. 3
D. 4
ANSWER: C (3)
3. Element Y has two isotopes Y and Y present in the ratio 1:3. The relative atomic mass of Y would be
A. 20.5
B. 21
C. 21.5
D. 22
ANSWER: C (21.5)
4. 100.0g of KClO3 was added to 40.0 cm^3 of water to give a saturated solution at 298K. If the solubility of the salt is 20.0 moldm^-3 at 298K, what percentage of the salt is left undissolved? {K= 39, Cl = 35.5, O = 16}
A. 80%
B. 60%
C. 5%
D. 2%
5. Elements X and Y have electronic configuration 1S22S22P4 and 1S22S22P63S23P1 respectively. When they combine the formula of the compound formed is
A. XY
B. Y2X3
C. Y2 X3
D. Y X2
ANSWER: B (Y2X3)
Recommended: WAEC Timetable
6. A solution of 0.20 mole of NaBr and 0.20 mole of MgBr2 in 2.0 dm3 of water is to be analysed. How many moles of Pb(NO3 )2 must be added to precipitate all the bromide as insoluble PbBr2
A. 0.30 mol
B. 0.10 mol
C. 0.20 mol
D. 0.40 mol
ANSWER: A (0.30 mol)
7. Na2CO3 + HCl —-> NaHCO3 + NaCl. The indicator most suitable for this reaction should have pH equal to.
A. 3
B. 5
C. 7
D. 9
ANSWER: D (9)
8. A satuarted solution of silver trioxocarbonate (IV), was found to have concentration of 1.30 x 10-5 moldm-3 . The solubility product of the trioxocarbonate (IV) is
A. 8.79 x 10-15
B. 1.69 x 10-10
C. 1.82 x 10-11
D. 9.84 x 10-10
ANSWER: A (8.79 x 10-15)
9. When platinum electodes are used during the electrolysis of copper (II) tetraoxosulphate (IV) solution, the solution gets progressive
A. Acidic
B. Basic
C. Neutral
D. Atmospheric
ANSWER: A (Acidic)
10. Tetraoxosulphate (VI) ions are final test using
A. acidified silver nitrate
B. acidic barium chloride
C. lime water
D. dilute hydrochloric acid
ANSWER: D (dilute hydrochloric acid)
See:
- WAEC Physics Questions and Answers
- WAEC Biology Questions and Answers
- WAEC English Questions and Answers
WAEC 2020 Chemistry Theory Questions
PAPER 2 (ESSAY)
SECTION A
1. Identify the solid remaining when each of the following is heated.
(a) lithium trioxonitrate (V)
(b) potassium trioxonitrate (V)
(c) calcium trioxonitrate (V)
2. (a) When calcium oxide and coke are heated in an electric furnace, the products are carbon (ii) oxide and calcium carbide (CaC2), write the equation for this reaction.
(b) The addition of water to calcium carbide leads to the formation of calcium hydroxide and ethyne. Write the equation for the production of ethyne.
3. Calculate the percentage by mass of silicon tetrachloride. [2 marks]
4. Ammonia, NH3, and phosphine, Ph3, are the hydrides of the first two elements in group 5.
(a) Draw a dot and cross diagram for the ammonia molecule. [2 marks]
(b) Sketch and explain the shape of the ammonia molecule. [3 marks]
5. The first ionization energy of chlorine is +1260KJmol-1.
(a) Define the term first ionization energy.
(b) State and explain the general trend in the values of the first ionization energy for the elements across the period, sodium to argon in the periodic table.
6. Compound A consisting of carbon and hydrogen only. The compound was found to contain 80% carbon by mass.
(a) Calculate the empirical formula of compound A using the data above.
(b) The relative molecular mass of compound A was found to be 30.
Use this information to deduce the molecular formula of compound A.
[H = 1.00 C = 12.00]
7. State two factors other than a change in temperature or the use of a catalyst that influence the rate of a chemical reaction.
SECTION B
1. (a) Two elements represented by the letters Q and R have atomic numbers 9 and 12 respectively.
(i) Write the election configuration of R.
(ii) To what group does Q belong in the periodic table.
(iii) Write the formula of the compound formed when Q combines with R.
(iv) Explain briefly, why Q is a good oxidizing agent.
(v) State whether R would be expected to form acidic or basic oxide.
(b) (i) State two assumptions of the kinetic theory of gases.
(ii) When some solids are heated, they change directly into the gaseous state. What name is given to this phenomenon?
(iii) List two substances which exhibit the phenomenon mentioned in (ii).
(iv) Write an expression to show the mathematical relationship between the rate of diffusion of a gas and its vapour.
2. An aqueous solution has a pH of 4.0.
(a) (i) What is the hydrogen ion concentration of the solution?
(ii) What effect will it have on litmus paper?
(iii) Which of the following salt solutions would have the same effect on litmus? Give a reason for your answer. NH4Cl(aq); NaCl(aq) ; CH3OON(aq).
(b) (i) Differentiate between a fine chemical and a heavy chemical.
(ii) Name two sources of air pollution.
(iii) Suggest one way of reducing air pollution in cities
3. (a) (i) Explain briefly the fermentation process.
(ii) Write a balanced equation for the fermentation of glucose.
(iii) What substance must be added to glucose solution to ferment it?
(iv) Explain briefly why tightly corked glass filled to the brim with palm wine shatters on standing.
(b) State one industrial application of each of the following methods of separation:
(i) Crystallization;
(ii) Fractional distillation.
(c) Explain the following terms:
(i) Saponification;
(ii) Esterification.
(d) Write a balanced equation to illustrate each of the terms in (c).
(e) i) What is hydrocarbon compound?
(ii) Name two principal sources of hydrocarbons.
WAEC Chemistry Essay and Objective 2021 (EXPO)
The above questions are not exactly 2021 WAEC Chemistry questions and answers but likely WAEC Chemistry repeated questions and answers.
These questions are for practice. The 2021 WAEC Chemistry expo will be posted on this page during the WAEC Chemistry examination. Keep checking and refreshing this page for the answers.
Today’s Chemistry Answers
Chemistry Objective Answers (2020 Answers)
1-10: CACDBDADAD
11-20: AADCDABBCD
21-30: BACBCCBCAC
31-40: CBACBCDBAD
41-50: DBBDCBCCCB
(1ai)
Faraday’s First Law of Electrolysis states that the chemical deposition due to the flow of current through an electrolyte is directly proportional to the quantity of electricity (coulombs) passed through it.
(1aii)
Strong electrolytes ionize completely (100%), while weak electrolytes ionize only partially.
(1b)
CHEMICAL PROPERTY OF EHYNE
– COMBUSTION REACTION: Ethyne burns in air with a luminous smoky flame and hence used for lightening purpose.
2C2H2 + 5O2 —–> 4CO2 + 2H2O + heat
(1c)
Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent bonds between adjacent carbon atoms.
(1cii)
CH3COOH + CH3OH–>CH3COOCH3 + H2O
(1ciii)
methly ethanoate
(1d)
By removing the main product continuously.
(1e)
Mzn = 3.75g
Mzn = 65.0g/mol
n= m/M=3.75/65.0
n=0.0577mole
nH² =0.0577mole because the mole ratio is the same
np =n*L
np=0.0577*6.02*10^23
np=3.47*10^22 moles
(1d)
Addition of catalysis I;e it catalyzed by a high concentration of hydrogen ion
(1f)
Flooding
(1gi)
Reaction C
(1gii)
Zinc (from + 2 to + 4)
(1hi)
(i)Each spectral line is caused by one electron
(ii)Electron can exist only in circular orbit of definite quantum energy.
(1hii)
It could not account for the spectrum at note complicated atoms
(1i)
(i)Temperature of the reacting system
(ii)Pressure of the reacting system
(iii)Concentration of the reacting system
(1j)
Both liberate carbon(iv) oxide
One produce a chloride salt , the other produce an ethronate salt
2ai)
The relationship between the compounds A and B is that they have similar chemical properties
(2aii)
– A : Trans-1,2-dichloroethene
– B : Cis-1,2-dichloroethene
(2aiii)
Their chemical properties will be the same
(2aiv)
The reason is because they are geometric isomers. Geometric isomers have the same chemical properties but different physical properties.
2bi)
(i) Temperature remains constant during boiling
(ii) There is change of state during boiling
(2bii)
I – It will increase the boiling point of water.
II – It will reduce the boiling point of water.
(2biii)
Boiling occurs at a specific temperature While Evaporation occurs at almost all temperatures.
(2ci)
An unsaturated solution is one that contains less than the maximum amount of solute that can dissolve at a given temperature While A saturated solution is one that contains maximum of solute that can be dissolved in it at that temperature.
(2cii)
(i) By increasing the temperature of the solution.
(ii) By increasing the amount of the solute.
(2ciii)
Temperature.
(2di)
Mole is a standard scientific unit for measuring large quantities of very small entities such as atoms, molecules, or other specified particles
(2dii)
MgO(s)+2HCl(aq) —> MgCl(aq)+H2O(l)
From the equation of reaction; 1 mole of MgO = 2 moles of HCl
Hence n = cv/100
where c = 0.1moldm-³; v = 25.0cm³
No of mole of HCl = n = 0.1×25/1000
= 2.5 x 10-³ moles
Hence the no of moles ofMgO required = 2.5/2 x10-³
But n = m/M = reacting mass/ Molar mass —> m = nM = 1.25×10-³ x 40
= 50 x 10-³ = 0.05g of MgO.
(2e)
(i) They are malleable
(ii) They are ductile
(iii) They are good conductors of heat and electricity
=====================
3ai)
Draw the diagram
(3aii)
I. Activation Energy = (210 – 100)KJ = 110K
II. Hp – HR = ΔH
54 – 100 = -46KJ
(3aiii)
Q2(g) + R2(g) –> 2QR(g)
(3aiv)
Exothermic reaction.
(3av)
The heat content of the reactant is higher than that of the product.
(3bi)
E7 – 1s² 2S² 2P³
F9 – 1s² 2S² 2P⁵
G12 – 1S² 2S² 2P⁶ 3S²
H13 – 1S² 2s² 2P⁶ 3S² 3P¹
(3bii)
I. G and H
II. H
III. F
IV. GF2
(3ci)
Isotopy is the existence of an element in more than one physical form with the same atomic number but different atomic masses.
(3d)
(i) Atoms
(ii) Molecules
(iii) ions
5ai)
(i) Ammonia (NH3)
(ii) Hydrogen chloride gas(HCl)
(5aii)
To show that hydrogen chloride is extremely soluble in water.
(5aiii)
Fill a round-bottomed flask with dry hydrogen chloride through a tube A and air through another tube B. Add a few drops of water through B and close the tubes. Invert the flask into a trough of water containing blue litmus solution. The water turns red.
(5bi)
Petrochemical industries.
Pharmaceutical industries.
(5bii)
(i) Pollution of water bodies by chemical waste.
(ii) Pollution of air.
(iii) Radioactive particles are released.
(5ci)
(i) Coke.
(ii) Coal tar.
(iii) Coal gas.
(5cii)
(i) Coal gas –> Importsmt gaseous fuel.
(ii) Coke –> Used as a reducing agent.
(5di)
(i) Calcium tetraoxosulphate(vi)
(ii) Calcium hydrogentrioxocarbonate(iv)
(5dii)
(i) By boiling.
(ii) Addition of caustic Soda.
(5diii)
(i) Hard water contains dissolved minerals and therefore tastes better.
(ii) The calcium salts on hard water help animals to build strong teeth and bones
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Tips to Pass WAEC Chemistry Questions
1. Study Hard
It is known to everyone that hardwork brings success. Ensure to read the chemistry textbooks recommended by The West Africa Examination Council (WAEC).
This will help you to take a look at most of the questions you will see in the day of WAEC Chemistry examination.
Let me clearly state that questions are not imported from heaven but from those textbooks recommended by WAEC.
2. Read WAEC Chemistry Past Questions
WAEC usually picks questions from the previous years to form fresh questions. Studying WAEC Chemistry past questions would give you an idea of how WAEC Chemistry questions are set.
3. Start Preparing for WAEC 2021 :
Stop wasting your time. Now that you have gotten textbooks and past questions, the next thing is to begin your reading. Early reading and practice is good for you; you will pass well on WAEC 2021 Chemistry
4. Solve and try to understand every example and exercise you see in textbooks
It is very unfortunate that Secondary school students are fond of skipping exercises and even examples while studying textbooks.
They loved notebooks so much that they could ask, “can I read my Chemistry notebook and pass WAEC 2021?”. Don’t be scared of attempting exercises; they are there to help you. Face it and overcome it!
5. Practise Regularly
Don’t get discouraged when certain topics are annoying, keep on practicing until you master everything. Never give up and never say never. Keep pushing….
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