Chemistry past questions: WAEC SSCE 2023

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

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

1.
A compound that could be dried by using conc. tetraoxosulphate (VI) acid and not by calcium oxide is likely to be
1. A.a deliquescent salt
2. B.a neutral salt
3. C.an alkaline gas
4. D.an acid anhydride
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Answer: D an acid anhydride
2.
A consequence of global warming is
1. A.air pollution
2. B.High Humidity
3. C.flooding
4. D.Water pollution
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Answer: C flooding
3.
A mixture containing two salts of different solubility can be separated by
1. A.chromatography.
2. B.crystallization.
3. C.distillation.
4. D.evaporation.
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Answer: B crystallization.
4.
Alkenes can be manufactured by
1. A.the combustion of alkanes.
2. B.the cracking of hydrocarbons.
3. C.polymerization reactions.
4. D.addition of hydrogen to unsaturated vegetable oils.
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Answer: B the cracking of hydrocarbons.
5.
An element X has two isotopes, \(^{65}X_{30}\) and \(^{66}X_{30}\) with relative abundance of 60 % and 40% respectively. The relative atomic mass of X is
1. A.66.00
2. B.65.50
3. C.65.00
4. D.65.40
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Answer: D 65.40
6.
An example of a crystalline substance that does not possess water of crystallization is
1. A.potassium trioxonitrate (V)
2. B.sodium tetraoxosulphate (VI)
3. C.iron (II) tetraoxosulphate (VI)
4. D.sodium trioxocarbonate (IV)
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Answer: B sodium tetraoxosulphate (VI)
7.
Arrange the following compounds in decreasing order of their boiling points: \(NH_3\) , HF, \(SiH_4\) , \(CH_4\)
1. A.HF, \(NH_3\) , \(SiH_4\) , \(CH_4\)
2. B.\(CH_4\) , \(SiH_4\) , HF, \(NH_3\) ,
3. C.\(NH_3\) , \(CH_4\) , \(SiH_4\) , HF
4. D.\(CH_4\) , \(SiH_4\) , \(NH_3\) , HF
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Answer: A HF, \(NH_3\) , \(SiH_4\) , \(CH_4\)
8.
Carbon is deposited in the exhaust pipes of cars because of
1. A.presence of additives in petrol
2. B.incomplete combustion of petrol
3. C.presence of carbon in petrol
4. D.contamination of petrol with diesel
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Answer: B incomplete combustion of petrol
9.
Consider the following reaction equation: \(2SO_3(g) → 2SO_2(g) + O_2\) (g) ∆H = +198 kJ/mol Which of the following statements about the reaction is correct?
1. A.198 kJ of energy is given off
2. B.The reaction is exothermic
3. C.The reaction container would feel warm
4. D.198 kJ of energy is absorbed
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Answer: D 198 kJ of energy is absorbed
10.
Copper (II) ions are able to participate in co-ordinate covalent bonding because they
1. A.are coloured
2. B.are positively charged
3. C.have vacant d-orbital
4. D.have unpaired electrons
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Answer: C have vacant d-orbital
11.
Determine the volume of 0.100 mol of HCl in \(0.250 mol dm^3\) of solution.
1. A.\(200cm^3\)
2. B.\(100cm^3\)
3. C.\(20cm^3\)
4. D.\(400cm^3\)
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Answer: D \(400cm^3\)
12.
Dilute trioxonitrate (V) acid does not produce hydrogen when it reacts with metals because
1. A.it reacts with the product.
2. B.it is highly corrosive.
3. C.there is no visible reaction.
4. D.it is a strong oxidizing agent.
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Answer: D it is a strong oxidizing agent.
13.
Going down group II in the periodic table normally
1. A.ionization energy increases
2. B.melting point increases
3. C.shielding effect decreases
4. D.electronegativity increases
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Answer: B melting point increases
14.
How many grammes of NaOH(s) would be needed to produce 100.0 cm3 of a 0.20 mol dm-3 NaOH, (aq)? [NaOH = 40.0]
1. A.800.0g
2. B.0.02 g
3. C.20.0 g
4. D.0.80 g
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Answer: D 0.80 g
15.
How many moles are there in 3.0 g of \(O_2\) ? [O = 16.0]
1. A.0.0093 moles.
2. B.0.0930 moles.
3. C.0.0625 moles.
4. D.0.6250 moles.
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Answer: B 0.0930 moles.
16.
How many moles of copper would be deposited by passing 1 Faraday of electricity through a \(CuCl_2\) solution?
1. A.2 moles
2. B.0.5moles
3. C.0.025moles
4. D.1 mole
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Answer: B 0.5moles
17.
How many unpaired electrons are present in \(_{26}Fe^{3+}\) ?
1. A.4
2. B.2
3. C.3
4. D.5
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Answer: D 5
18.
If \(100^3\) of a saturated solution of sodium tetraoxosulphate (VI) at 30° C contains 10.5 g of the salt, what would be its solubility at this temperature? [( \(Na_2SO_4\) = 142]
1. A.2.15 mol dm-3
2. B.0.74 mol dm-3
3. C.0.60 mol dm-3
4. D.0.57 mol dm-3
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Answer: B 0.74 mol dm-3
19.
Isoelectronic species have the same number of
1. A.ions
2. B.electrons
3. C.protons
4. D.neutrons
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Answer: B electrons
20.
Petrochemistry is an example of
1. A.applied chemistry
2. B.Biochemistry
3. C.Pure chemistry
4. D.Environmental chemistry
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Answer: A applied chemistry
21.
Positive ions in a sea of electrons are found in
1. A.covalent bonds
2. B.metallic bonds
3. C.dative bonds
4. D.ionic bonds
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Answer: B metallic bonds
22.
Species that occur in a reaction pathway but not in the overall reaction are known as
1. A.Reactants
2. B.Inhibitors
3. C.Products
4. D.Intermediates
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Answer: D Intermediates
23.
The best indicator to use for the titration of ethanoic acid with sodium hydroxide is
1. A.methyl orange
2. B.phenolphthalein
3. C.screened methyl orange
4. D.methyl red
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Answer: B phenolphthalein
24.
The following statements are correct except
1. A.energy is released when liquids change to solids.
2. B.carbon atoms in gaseous methane are further apart than those in solid diamond.
3. C.there is large decrease in the volume of a solid metal when pressure is applied to it.
4. D.particles move faster in the gaseous state than in the liquid state.
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Answer: C there is large decrease in the volume of a solid metal when pressure is applied to it.
25.
The following steps are scientific methods except
1. A.experimentation
2. B.problem identification
3. C.Analysis
4. D.Open-mindedness
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Answer: D Open-mindedness
26.
The formation of a bond between hydrogen and a highly electronegative atom results in
1. A.polarity
2. B.electrovalent bond
3. C.dipole
4. D.metallic bond
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Answer: A polarity
27.
The gas that is less dense than air is
1. A.nitrogen
2. B.chlorine
3. C.Carbon(IV) oxide
4. D.Oxygen
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Answer: A nitrogen
28.
The molecule that has a non-polar covalent bond is
1. A.HCl
2. B.\(NH_3\)
3. C.\(Cl_2\)
4. D.\(H_2O\)
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Answer: C \(Cl_2\)
29.
The pair of compounds that belongs to the same homologous series is
1. A.\(C_2H_6\) and \(C_4H_{10}\)
2. B.\(C_3H_8\) and \(C_3H_6\)
3. C.\(C_2H_4\) and \(C_4H_{10}\)
4. D.\(C_4H_{10}\) and \(C_5H_{10}\)
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Answer: A \(C_2H_6\) and \(C_4H_{10}\)
30.
The periodic property that is used to determine whether a covalent molecule is polar or not is
1. A.atomic radius
2. B.ionization energy
3. C.electron affinity
4. D.electronegativity
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Answer: D electronegativity
31.
The primary component of natural gas
1. A.ethane
2. B.methane
3. C.butane
4. D.propane
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Answer: B methane
32.
The reduction half equation of the following reaction is: \(Zn_{(s)} + CuSO_{4(aq)} → ZnSO_{4(aq)} + Cu_{(s)}\)
1. A.\(Zn_{(s)} → Zn^{2+}_{(aq)} + 2e^-\)
2. B.\(CuSO_{4(s)} + H_2O_{(l)}\) → \(Cu^{2+}_{(aq)}\) + \(SO_{4(aq)}^{2-}\)
3. C.\(Cu^{2+}_{(aq)} + 2e^- → Cu_{(s)}\)
4. D.\(Cu^{2+}_{(aq)} + e^- → Cu_{(s)}\)
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Answer: C \(Cu^{2+}_{(aq)} + 2e^- → Cu_{(s)}\)
33.
The relative molar mass of a gaseous hydrocarbon is 30. Determine its vapour density.
1. A.45
2. B.30
3. C.15
4. D.60
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Answer: C 15
34.
The salt solution formed firm a reaction between ethanoic acid and sodium hydroxide solution would be
1. A.amphoteric
2. B.neutral
3. C.basic
4. D.acidic
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Answer: C basic
35.
The separation technique that is suitable for separating iodine from tetrachloromethane is
1. A.solvent extraction
2. B.decantation
3. C.fractional distillation
4. D.filtration
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Answer: A solvent extraction
36.
The vapour density of an organic compound with the molecular formula \(C_2H_4O_2\) , is [H=1.0, C=12.0, O= 16.0]
1. A.40
2. B.120
3. C.65
4. D.30
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Answer: D 30
37.
Thermal cracking of alkanes usually
1. A.is an exothermic process
2. B.produces only small alkanes
3. C.involves decomposition
4. D.requires hydrogen
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Answer: C involves decomposition
38.
What takes place at the cathode during electrolysis?
1. A.Anions lose electrons
2. B.Anions are oxidized
3. C.Cations are oxidized
4. D.Cations are discharged
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Answer: D Cations are discharged
39.
Which of the elements in the table below would react more readily with chlorine?
Element Ionization energy (KJ \(mol^{-1} \times 10^{-3}\) )
W 12.0
X 21.0
Y 106.0
Z 200.0
1. A.Y and Z only
2. B.X and Z only
3. C.W and X only
4. D.W and Z only
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Answer: C W and X only
40.
Which of the following elements has its valence electrons in the s-orbital?
1. A.Aluminum
2. B.Phosphorus
3. C.Sodium
4. D.Carbon
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Answer: C Sodium
41.
Which of the following equations does not illustrate correctly one of the reactions of chlorine?
1. A.\(Ca(OH)_2 + Cl_2 → CaOCl_2 + H_2O\)
2. B.\(Cl_2 + 2NaF → 2NaCl + F_2\)
3. C.\(Cl_2 + 2NaOH → NaCl + NaClO + H_2O\)
4. D.\(H_2S + Cl_2 → 2HCl + S\)
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Answer: B \(Cl_2 + 2NaF → 2NaCl + F_2\)
42.
Which of the following equimolar solutions has the highest conductivity?
1. A.\(H_2SO{_4(aq)}\)
2. B.\(NaOH{_(aq)}\)
3. C.\(H_2CO{_3(aq)}\)
4. D.\(CH_3COOH{_4(aq)}\)
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Answer: A \(H_2SO{_4(aq)}\)
43.
Which of the following gases has the lowest rate of diffusion? [H=1.0, C=12.0, N = 14.0, O= 16.0]
1. A.Nitrogen
2. B.methane
3. C.Ammonia
4. D.Oxygen
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Answer: D Oxygen
44.
Which of the following laws or theory cannot be explained by the application of the kinetic theory of gases?
1. A.Dalton's atomic theory
2. B.Charle's law
3. C.Boyle's law
4. D.Gay- Lussac's law
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Answer: A Dalton's atomic theory
45.
Which of the following properties does not give evidence of the kinetic theory of matter?
1. A.Diffusion
2. B.Melting
3. C.Polymerization
4. D.Evaporation
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Answer: C Polymerization
46.
Which of the following reactions represents the hydrolysis of an alkanoate?
1. A.\(CH_3COOH + OH^- ⇌H^+⇌ CH_3COO^- + H_2O\)
2. B.\(CH_3COOH + C_2H_5OH ⇌H^+⇌ CH_3COOC_2H_5 + H_2O\)
3. C.\(CH_3COOC_2H_5 + H_2O ⇌H^+⇌ CH_3COO^- + CH_3CH_2OH\)
4. D.\(CH_3COOCH_2CH_3 + H_2O ⇌H^+⇌ CH_3COOH + CH_3CH_2OH\)
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Answer: D \(CH_3COOCH_2CH_3 + H_2O ⇌H^+⇌ CH_3COOH + CH_3CH_2OH\)
47.
Which of the following statements about the collision theory is correct?
1. A.Ineffective collision brings about chemical reaction
2. B.All collisions bring about reactions
3. C.The rate of reaction is proportional to the number of effective collisions
4. D.Collision of molecules will split the molecules to react
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Answer: C The rate of reaction is proportional to the number of effective collisions
48.
Which of the following statements is correct?
1. A.Addition reactions occur between alkanes and chlorine
2. B.Butane has a lower boiling point than propane
3. C.Pentane has five isomers
4. D.An alkane with 49 carbon atoms contains 100 hydrogen atoms
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Answer: D An alkane with 49 carbon atoms contains 100 hydrogen atoms
49.
Which of the statements about gases is not correct?
1. A.Gases have low densities compared to solids and liquids of equal mass
2. B.The total kinetic energy of the gas is not affected by collision
3. C.Molecules of the gas are in constant motion
4. D.Gases are highly soluble in water at high temperatures
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Answer: D Gases are highly soluble in water at high temperatures
50.
Why are \(H_2SO_4\) and \(CaCl_2\) , not suitable for drying ammonia gas? They
1. A.are poisonous
2. B.pollute the gas
3. C.are corrosive
4. D.react with the gas
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Answer: D react with the gas

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Element	Ionization energy (KJ \(mol^{-1} \times 10^{-3}\) )
W	12.0
X	21.0
Y	106.0
Z	200.0