Chemistry past questions: WAEC SSCE 2021

48 objective questions, with answers. Free to read and practise.

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48 questions, one at a time, marked as you go or at the end. No account needed.

1.
A coordinate covalent bond could be formed between?
1. A.NH \(_{3}\) and PCl \(_{3}\)
2. B.BCl \(_{3}\) and AlCl \(_{3}\)
3. C.BCl \(_{3}\) and NH \(_{3}\)
4. D.H \(^{+}\) and AlCl \(_{3}\)
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Answer: C BCl \(_{3}\) and NH \(_{3}\)
2.
A molecular of phosphorus is
1. A.diatomic
2. B.triatomic
3. C.tetraatomic
4. D.monoatomic
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Answer: C tetraatomic
3.
An element, Q, contains 69% of \(^{63}\) Q and 31% of \(^{65}\) Q. What is the relative atomic mass of Q?
1. A.63.0
2. B.63.6
3. C.65.0
4. D.69.0
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Answer: B 63.6
4.
Cathodic protection of metals is based on
1. A.standard electrode potential of hydrogen
2. B.its electrical conductivity
3. C.nature of oxides formed
4. D.relative tendencies of oxidation
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Answer: D relative tendencies of oxidation
5.
Consider the structure above How many carbon atoms does the parent chain contain?
1. A.5
2. B.4
3. C.3
4. D.2
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Answer: B 4
6.
Electrovalent compounds normally ------------
1. A.have low boiling points
2. B.have mobile electrons
3. C.conduct electricity in the solid state
4. D.dissolve in polar solvent
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Answer: D dissolve in polar solvent
7.
Elements with high ionization energies would-------
1. A.lose electrons easily
2. B.have large atomic radii
3. C.have high effective nuclear charges
4. D.have low atomic numbers
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Answer: C have high effective nuclear charges
8.
How many coulombs of electricity would liberate 1.08g of Ag from a solution of silver salt? [Ag = 108.0; 1F = 96500 C]
1. A.96500 C
2. B.9650 C
3. C.965 C
4. D.9.65 C
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Answer: C 965 C
9.
How many molecules of oxygen would occupy a volume of 2.24 cm \(^{3}\) at s.t.p? [Molar volume at s.t.p = 22,400 cm \(^{3}\) , Avogadro's number = 6.02 x 10 \(^{23}\) ]
1. A.3.01 x 10 \(^{20}\)
2. B.3.01 x 10 \(^{27}\)
3. C.6.02 x 10 \(^{19}\)
4. D.6.02 x 10 \(^{27}\)
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Answer: C 6.02 x 10 \(^{19}\)
10.
If humid air is polluted by chlorine discharged, the air can be restored by sprinkling
1. A.solid MnO \(_{2}\)
2. B.acidified KMnO \(_{4}\)
3. C.acidified FeSO \(_{4}\)
4. D.saturated NaCl(aq)
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Answer: B acidified KMnO \(_{4}\)
11.
Potassium trioxonitrate (V) can be obtained from its solution by----------
1. A.distillation
2. B.evapoartion
3. C.crystallization
4. D.filtration
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Answer: C crystallization
12.
Protons and electrons are called fundamental particles because they----------
1. A.are indivisible
2. B.have different charges
3. C.are the lightest particles
4. D.are found in all matter
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Answer: D are found in all matter
13.
Study the graphs below and use them to answer the question below [img: Open photo] Which of the following illustrates the variation of the rate of evolution of gas from a given length of magnesium ribbon (y-axis) with an increase in the concentration of the added (x-axis)?
1. A.I
2. B.II
3. C.III
4. D.IV
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Answer: A I
14.
The 25°C evaporation of a 100 cm \(^{3}\) solution of K \(_{2}\) CO \(_{3}\) to dryness gave 14g of the salt. What is the solubility of K \(_{2}\) CO \(_{3}\) at 25°C? [K \(_{2}\) CO \(_{3}\) = 138]
1. A.0.01 mol dm \(^{-3}\)
2. B.0.101 mol dm \(^{-3}\)
3. C.1.01 mol dm \(^{-3}\)
4. D.10.0 mol dm \(^{-3}\)
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Answer: C 1.01 mol dm \(^{-3}\)
15.
The activation energy of the reaction is
1. A.E \(_{A}\)
2. B.E \(_{B}\)
3. C.E \(_{C}\)
4. D.E \(_{D}\)
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Answer: C E \(_{C}\)
16.
The alkanol represented by the structure above is
1. A.primary and dihydric
2. B.secondary and monohydric
3. C.tertiary and dihydric
4. D.secondary and dihydric
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Answer: A primary and dihydric
17.
The basic property of salts used as drying agents is by?
1. A.efforescence
2. B.high melting point
3. C.hygroscopy
4. D.low solubility
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Answer: C hygroscopy
18.
The Bohr model of the atom proposed the existence of?
1. A.the nucleus
2. B.electron shells
3. C.nucleons
4. D.neutrons
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Answer: B electron shells
19.
The collision between ideal gas molecules are considered to be perfectly elastic because
1. A.they collide without losing energy
2. B.they move randomly in a straight line
3. C.their average kinetic energy is variable
4. D.the distance between them is large compared to their size
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Answer: A they collide without losing energy
20.
The energy profile diagram illustrates-------------
1. A.an endothermic reaction
2. B.an exothermic reaction
3. C.a spontaneous reaction
4. D.a redox reaction
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Answer: B an exothermic reaction
21.
The enthalpy change of the reaction is------------
1. A.E \(_{A}\)
2. B.E \(_{B}\)
3. C.E \(_{C}\)
4. D.E \(_{D}\)
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Answer: D E \(_{D}\)
22.
The following ions have the same electron configuration except \(_{8}\) O, \(_{12}\) Mg, \(_{13}\) AI, \(_{17}\) CI
1. A.CI \(^{-}\)
2. B.O \(^{2-}\)
3. C.Mg \(^{2+}\)
4. D.AI \(^{3+}\)
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Answer: A CI \(^{-}\)
23.
The formation of ethene from dehydration of ethanol can be described as-------
1. A.an addition reaction
2. B.an elimination reaction
3. C.an oxidation reaction
4. D.a substitution reaction
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Answer: B an elimination reaction
24.
The hydrolysis of proteins by diluting mineral acids produces
1. A.sucrose
2. B.glucose
3. C.amino acids
4. D.fatty acids
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Answer: C amino acids
25.
The isotopes of neon are represented by the symbols \(^{20}\) \(_{x}\) Ne, \(^{21}\) \(_{y}\) Ne, and \(^{22}\) \(_{z}\) Ne. The relationship between x, y, and z is?
1. A.x > y > z
2. B.x < y < z
3. C.x = y= z
4. D.x < z < y
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Answer: C x = y= z
26.
The most common method of preparing insoluble salts is by
1. A.filtration
2. B.decomposition
3. C.neutralization
4. D.double decomposition
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Answer: D double decomposition
27.
The ratio of carbon atoms of hydrogen atoms in a hydrocarbon is 1:2. If its molecular mass is 56, what is its molecular formula?
1. A.C \(_{3}\) H \(_{6}\)
2. B.C \(_{4}\) H \(_{8}\)
3. C.C \(_{2}\) H \(_{4}\)
4. D.CH \(_{2}\)
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Answer: B C \(_{4}\) H \(_{8}\)
28.
The reactivity of fluorine is high because of
1. A.its high electronegativity
2. B.the small size of the fluorine atom
3. C.the availability of d-orbitals
4. D.the strong F-F bond
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Answer: A its high electronegativity
29.
The region around the nucleus where electrons can be located is called?
1. A.a spectra
2. B.an orbital
3. C.a quanta
4. D.a field
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Answer: B an orbital
30.
Under which conditions of pressure (p) and temperature (T) would the volume of an inflated ballon increase? When
1. A.P and T are increased
2. B.both T and P are decreased
3. C.T is increased and P is decreased
4. D.T is decreased and P is increased
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Answer: C T is increased and P is decreased
31.
What is the concentration of a solution which contains 0.28g of potassium hydroxide in 100 cm \(^{3}\) of solution [KOH = 56]
1. A.0.01 mol dm \(^{-3}\)
2. B.0.05 mol dm \(^{-3}\)
3. C.0.10 mol dm \(^{-3}\)
4. D.0.50 mol dm \(^{-3}\)
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Answer: B 0.05 mol dm \(^{-3}\)
32.
What is the empirical formula of a hydrocarbon containing 0.160 moles of carbon and 0.640 moles of hydrogen
1. A.CH \(_{2}\)
2. B.CH \(_{3}\)
3. C.CH \(_{4}\)
4. D.C \(_{2}\) H \(_{4}\)
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Answer: C CH \(_{4}\)
33.
What is the relative molecular mass of the compound below? [img: What is the relative molecular mass of the compound below [H = 1.0; C = 12.0; O = 16.0] - SchoolNGR] [H = 1.0; C = 12.0; O = 16.0]
1. A.137
2. B.136
3. C.64
4. D.59
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Answer: B 136
34.
What number of moles of oxygen would exert a pressure of 10 atm at 320 K in an 8.2 dm \(^{2}\) cylinder? [R = 0.082 atm dm \(^{3}\) mol \(^{-1}\) K \(^{-1}\) ]
1. A.0.32
2. B.1.56
3. C.3.13
4. D.31.25
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Answer: C 3.13
35.
What would be observed when aqueous ammonia is added in drops and then in excess to a solution of copper(II) ions?
1. A.blue precipitate is formed which is soluble in excess ammonia
2. B.brick red precipitate is produced which is insoluble in excess ammonia
3. C.white precipitate is formed which is excess in ammonia
4. D.green precipitate is formed which is insoluble in excess ammonia
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Answer: A blue precipitate is formed which is soluble in excess ammonia
36.
When CuSO \(_{4(aq)}\) is added to Pb(NO \(_{3}\) ) \(_{2(aq)}\) --------
1. A.there would be no visible change
2. B.a blue precipitate would be formed
3. C.the resulting solution would become colourless
4. D.a white precipitate would be formed
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Answer: D a white precipitate would be formed
37.
Which of the following cell notations represent the diagram?
1. A.B \(^{2+}\) /B/ /A/A \(^{3+}\)
2. B.A \(^{3+}\) /A/ /B/B \(^{2+}\)
3. C.B/B \(^{2+}\) / /A/ \(^{3+}\)
4. D.A/A \(^{3+}\) / /B \(^{2+}\) /B
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Answer: D A/A \(^{3+}\) / /B \(^{2+}\) /B
38.
Which of the following gasses is highly soluble in water at room temperature
1. A.ammonia
2. B.carbon (IV) oxide
3. C.chlorine
4. D.nitrogen
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Answer: A ammonia
39.
Which of the following half reaction equations represent the reaction at the cathode
1. A.A \(^{3+_{(aq)}}\) +3e \(^{-}\) \(\rightarrow\) A \(_{(s)}\)
2. B.B \(^{2+_{(aq)}}\) +2e \(^{-}\) \(\rightarrow\) B \(_{(s)}\)
3. C.A \(_{(s)}\) \(\rightarrow\) \(^{3+_{(aq)}}\) +3e \(^{-}\)
4. D.B \(_{(s)}\) \(\rightarrow\) B \(^{2+_{(aq)}}\) + 2e \(^{-}\)
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Answer: B B \(^{2+_{(aq)}}\) +2e \(^{-}\) \(\rightarrow\) B \(_{(s)}\)
40.
Which of the following oxide causes acid rain?
1. A.CO
2. B.NO
3. C.H \(_{2}\) O \(_{2}\)
4. D.NO \(_{2}\)
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Answer: D NO \(_{2}\)
41.
Which of the following pairs of compounds would form a precipitate when their aqueous solutions are mixed?
1. A.NaCl and KNO \(_{3}\)
2. B.KCL and NaNO \(_{3}\)
3. C.K \(_{2}\) SO \(_{4}\) and BaCl \(_{2}\)
4. D.NH \(_{4}\) NO \(_{3}\) and CO \(_{3}\)
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Answer: C K \(_{2}\) SO \(_{4}\) and BaCl \(_{2}\)
42.
Which of the following pairs of molecules form hydrogen bonds?
1. A.C \(_{2}\) H \(_{5}\) OH and CH \(_{3}\) OH
2. B.CH \(_{3}\) OH and H \(_{2}\)
3. C.H \(_{2}\) S and CH \(_{4}\)
4. D.NH \(_{3}\) and SO \(_{2}\)
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Answer: A C \(_{2}\) H \(_{5}\) OH and CH \(_{3}\) OH
43.
Which of the following scientists discovered the electrons?
1. A.Joseph J. Thompson
2. B.James Chadwick
3. C.Amedeo Avogadro
4. D.Ernest Rutherford
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Answer: A Joseph J. Thompson
44.
Which of the following statements about elements in Group VII is correct?
1. A.Br \(_{2}\) will oxidize CI \(^{-}\)
2. B.F \(_{2}\) has the least tendency to be reduced
3. C.Cl \(_{2}\) will oxidize I \(^{-}\)
4. D.l \(_{2}\) is a stronger oxidizing agent than F \(_{2}\)
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Answer: C Cl \(_{2}\) will oxidize I \(^{-}\)
45.
Which of the following statements about Group VII elements is correct?
1. A.they are present in the same physical state
2. B.they are strong reducing agents
3. C.their reactivity decreases down the group
4. D.they exist as monoatomic molecules
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Answer: C their reactivity decreases down the group
46.
Which of the following statements is correct about ionization energy? It
1. A.decreases across the periods
2. B.results in the formation of an anion
3. C.causes Metalic nuclei to disintegrate
4. D.decreases down the group
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Answer: D decreases down the group
47.
Which of the graphs illustrates the variation of the pH of a given volume of strong acid solution (y-axis) with the volume of strong base titrated against its (x-axis)?
1. A.I
2. B.II
3. C.III
4. D.IV
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Answer: A I
48.
Which of the graphs illustrates the variation of the solubility of a salt in water (y-axis), with an increase in temperature (x-axis) if the dissolution process is exothermic?
1. A.I
2. B.II
3. C.III
4. D.IV
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Answer: D IV

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