Chemistry past questions: WAEC SSCE 2025

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 covalent hydride which does not exist as a gas at room temperature is
1. A.H \(_2\) O
2. B.BH \(_3\)
3. C.HCl
4. D.H \(_2\) S
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Answer: A H \(_2\) O
2.
A few drops of sodium hydroxide is added to an aqueous solution, a green precipitate is formed. The ion that may be present in the solution is
1. A.Cu \(^{2+}\)
2. B.Fe \(^{2+}\)
3. C.Fe \(^{3+}\)
4. D.NH \(_4\) \(^{+}\)
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Answer: B Fe \(^{2+}\)
3.
A salt that could be prepared by double decomposition is
1. A.sodium trioxocarbonate (IV)
2. B.barium trioxonitrate (V)
3. C.lead (II) trioxonitrate (V)
4. D.silver chloride
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Answer: D silver chloride
4.
Alkali metals are good conductors of heat and electricity because they
1. A.contain delocalised electrons
2. B.are found in the d-block
3. C.have vibrating ions
4. D.are all metals
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Answer: A contain delocalised electrons
5.
All the following compounds are covalent except
1. A.NO \(_2\)
2. B.SO \(_3\)
3. C.SO \(_2\)
4. D.KNO \(_3\)
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Answer: D KNO \(_3\)
6.
All the following compounds are ionic except
1. A.AgCl
2. B.KNO \(_3\)
3. C.NO \(_2\)
4. D.(NH \(_4\) ) \(_2\) CO \(_3\)
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Answer: C NO \(_2\)
7.
Aluminum is extracted by
1. A.electrolysis of the purified ore
2. B.froth floatation of the smelted ore
3. C.reduction of the ore with coke in a furnace
4. D.roasting the ore in excess supply of air
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Answer: A electrolysis of the purified ore
8.
Biotechnology is applied in the following processes except
1. A.baking of bread
2. B.production of wine
3. C.production of antibiotics
4. D.manufacturing of soap
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Answer: D manufacturing of soap
9.
Both Na \(^+\) and K \(^+\) have
1. A.tendency to give electrons
2. B.positive reduction potential
3. C.tendency to accept electrons
4. D.negative oxidation potential
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Answer: C tendency to accept electrons
10.
Empirical formula is the
1. A.simplest formula of a compound
2. B.molecular formula of a compound
3. C.chemical formula of a compound
4. D.structural formula of a compound
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Answer: A simplest formula of a compound
11.
Ethanol could be prepared in the laboratory by
1. A.reduction of ethanoic acid
2. B.oxidation of primary alkanol
3. C.oxidation of alkenes
4. D.hydration of ethene
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Answer: D hydration of ethene
12.
Exothermic reactions take place when energy given out in making bonds is
1. A.less than energy in for breaking bonds
2. B.more than energy taken in for breaking bonds
3. C.equal to the energy taken in for breaking bonds
4. D.remains the same as the energy taken in
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Answer: B more than energy taken in for breaking bonds
13.
Five d-orbitals have the same energy level in an isolated transition metal are described as
1. A.degenerate
2. B.non-degenerate
3. C.high level orbital
4. D.low-level orbital
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Answer: A degenerate
14.
How many pi-bond(s) is/are present in propene?
1. A.three
2. B.six
3. C.two
4. D.one
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Answer: D one
15.
If 25cm \(^3\) of a saturated solution contains 0.02 moles of the solute, determine the solubility of the solute.
1. A.5.0 X 10 \(^{-4}\) mol dm \(^{-3}\)
2. B.0.8 mol dm \(^{-3}\)
3. C.0.4 mol dm \(^{-3}\)
4. D.5.0 X 10 \(^{-2}\) mol dm \(^{-3}\)
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Answer: B 0.8 mol dm \(^{-3}\)
16.
If a gas occupies a volume of 400cm \(^3\) at a temperature of 400K and a pressure of 1 atm, at what temperature and pressure would its volume be 200cm \(^3\) ?
1. A.800 K and 1 atm
2. B.800 k and 0.5 atm
3. C.200 k and 1 atm
4. D.200 k and 0.5 atm
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Answer: C 200 k and 1 atm
17.
If acidified K \(_2\) Cr \(_2\) O \(_7\) acts as an oxidizing agent, the colour changes from
1. A.orange to red
2. B.yellow to green
3. C.orange to green
4. D.yellow to red
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Answer: C orange to green
18.
In a chemical reaction, ΔH is positive when
1. A.ΔH \(_{product}\) > ΔH \(_{reactants}\)
2. B.ΔH \(_{product}\) < ΔH \(_{reactants}\)
3. C.ΔH \(_{product}\) = ΔH \(_{reactants}\)
4. D.ΔH \(_{product}\) = 0
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Answer: A ΔH \(_{product}\) > ΔH \(_{reactants}\)
19.
In the electrolysis of dilute hydrochloric acid at the anode
1. A.Oxygen gas is given off
2. B.hydrogen gas is given off
3. C.chlorine gas is given off
4. D.hydrogen chloride gas is given off
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Answer: A Oxygen gas is given off
20.
In the periodic table, valence electrons are indicated by
1. A.group number
2. B.Shell number
3. C.period number
4. D.atomic mass
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Answer: A group number
21.
In the use of a universal indicator, red colour is an indication that the substance is a
1. A.concentrated acid
2. B.concentrated alkali
3. C.dilute acid
4. D.dilute base
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Answer: A concentrated acid
22.
In which of the following arrangements are the ions arranged in decreasing order of ionic size?
1. A.F \(^-\) ,Na \(^+\) , Mg \(^{2+}\) , Al \(^{3+}\)
2. B.Na \(^+\) , Mg \(^{2+}\) , Al \(^{3+}\) ,F \(^-\)
3. C.Al \(^{3+}\) , Na \(^+\) , Mg \(^{2+}\) , F \(^-\)
4. D.Al \(^{3+}\) , Mg \(^{2+}\) , Na \(^+\) , F \(^-\)
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Answer: A F \(^-\) ,Na \(^+\) , Mg \(^{2+}\) , Al \(^{3+}\)
23.
Iodine could be separated from the mixture of iodine and Calcium chloride by
1. A.Evaporation
2. B.Sublimation
3. C.fractional distillation
4. D.fractional crystallization
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Answer: B Sublimation
24.
Neutral atom of Neon with atomic number 10 is isoelectronic with
1. A.K \(^+\)
2. B.Mg \(^{2+}\)
3. C.Ca \(^{2+}\)
4. D.Li \(^+\)
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Answer: B Mg \(^{2+}\)
25.
Nickel is used in the hydrogenation of alkenes because it
1. A.Increases the yield of the product
2. B.lowers the activation energy of the reaction
3. C.makes the reaction more exothermic
4. D.prevents a reverse reaction from occuring
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Answer: B lowers the activation energy of the reaction
26.
Nucleons are sub-atomic particles which consist of
1. A.protons and neutrons
2. B.neutrons and electrons
3. C.protons and electrons
4. D.neutrons, protons and electrons
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Answer: A protons and neutrons
27.
Sodium chloride is used in the following processes except
1. A.treatment of water
2. B.manufacturing of chloride
3. C.preservation of food
4. D.separation of soap glycerol
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Answer: A treatment of water
28.
The allotrope of carbon used in the decolourization of sugar is
1. A.charcoal
2. B.graphite
3. C.lampblack
4. D.soot
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Answer: A charcoal
29.
The electron configuration of element Y is 1S \(^2\) 2S \(^2\) 2P \(^6\) 3S \(^2\) 3P \(^4\) . Y, therefore,
1. A.has mass number of 16
2. B.has three unpaired electron
3. C.belongs to period 4
4. D.belongs to group VI
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Answer: D belongs to group VI
30.
The filter in a cigarette reduces the amount of nicotine inhaled by
1. A.adsorption
2. B.absorption
3. C.burning
4. D.evaporation
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Answer: A adsorption
31.
The IUPAC name of the compound CH \(_3\) CHClCH \(_2\) OH is
1. A.chloropropanol
2. B.1-chloropropan-1-ol
3. C.2-chloropropan-3-ol
4. D.2-chloropropan-1-ol
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Answer: D 2-chloropropan-1-ol
32.
The lustre of a metal is due to its
1. A.high density
2. B.refractive density
3. C.chemical inertness
4. D.free electrons
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Answer: D free electrons
33.
The metal carbonate that would not decompose when heated strongly is
1. A.Al \(_2\) CO \(_3\)
2. B.CaCO \(_3\)
3. C.MgCO \(_3\)
4. D.Na \(_2\) CO \(_3\)
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Answer: D Na \(_2\) CO \(_3\)
34.
The nucleus of a hydrogen atom consists of
1. A.one proton only
2. B.one proton and one neutron
3. C.one neutron only
4. D.one electron only
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Answer: A one proton only
35.
The number of moles of KOH present in 200cm \(^3\) of 5.6 g dm \(^{-3}\) solution is [KOH = 56 g mol \(^{-1}\) ]
1. A.2.01
2. B.1.12
3. C.0.02
4. D.0.01
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Answer: C 0.02
36.
The percentage by mass of water in Na \(_2\) CO \(_3\) .10H \(_2\) O is [ Na \(_2\) CO \(_3\) .10H \(_2\) O = 286, H \(_2\) O = 18 ]
1. A.68.4%
2. B.62.9%
3. C.9.7%
4. D.6.3%
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Answer: B 62.9%
37.
When a hypothesis is proven within the limit of available evidence, it becomes a
1. A.scope
2. B.theory
3. C.principle
4. D.law
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Answer: B theory
38.
When C \(_2\) H \(_4\) molecule is polymerized, the polymer formed is
1. A.polyethene
2. B.polyethane
3. C.polypropene
4. D.polybutene
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Answer: A polyethene
39.
Which of the following alkanols is tertiary?
1. A.2-methylpentan-2-ol
2. B.2-methylpentan-1-ol
3. C.pentan-3-ol
4. D.pentan-2-ol
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Answer: A 2-methylpentan-2-ol
40.
Which of the following bonds is not an intermolecular force?
1. A.Hydrogen bond
2. B.Van der waal's
3. C.dipole-dipole
4. D.metallic bond
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Answer: D metallic bond
41.
Which of the following compounds would readily undergo addition reaction?
1. A.ethane
2. B.butene
3. C.ethanol
4. D.benzene
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Answer: B butene
42.
Which of the following conditions are necessary for the preparation of alkanoates from alkanols and alkanoic acids?
1. A.Water and NaOH
2. B.Conc. H \(_2\) SO \(_4\) and heat
3. C.NaOH and heat
4. D.Water and aqueous HCl
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Answer: B Conc. H \(_2\) SO \(_4\) and heat
43.
Which of the following elements is a metalloid?
1. A.Aluminium
2. B.Selenium
3. C.Phosphorus
4. D.Sodium
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Answer: B Selenium
44.
Which of the following elements is commercially obtained by the electrolysis of its fused salt?
1. A.Silver
2. B.Copper
3. C.Helium
4. D.Sodium
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Answer: D Sodium
45.
Which of the following gases is used in fire extinguishers?
1. A.Carbon(IV)oxide
2. B.Nitrogen(IV)oxide
3. C.Carbon(II)oxide
4. D.Sulphur(IV)oxide
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Answer: A Carbon(IV)oxide
46.
Which of the following metals would not release hydrogen when reacted with dilute HCl?
1. A.Calcium
2. B.Silver
3. C.Iron
4. D.Zinc
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Answer: B Silver
47.
Which of the following oxides is amphoteric?
1. A.CaO
2. B.MgO
3. C.BaO
4. D.BeO
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Answer: D BeO
48.
Which of the following oxides would form two different types of acids when dissolved in water?
1. A.CO \(_2\)
2. B.NO \(_2\)
3. C.SO \(_2\)
4. D.SO \(_3\)
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Answer: B NO \(_2\)
49.
Which of the following pairs of gases cannot be collected by downward delivery?
1. A.SO \(_2\) and NH \(_3\)
2. B.CO and N \(_2\)
3. C.Cl \(_2\) and N \(_2\)
4. D.SO \(_2\) and N \(_2\)
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Answer: B CO and N \(_2\)
50.
Which of the following species is the most powerful reducing agent?
1. A.Bromine atom
2. B.Chlorine atom
3. C.Fluoride atom
4. D.Iodine atom
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Answer: D Iodine atom

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