WAEC 2025 Chemistry | Objective

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Question 1 View Details
Which of the following pairs of gases cannot be collected by downward delivery?
Correct A. SO₂ and NH₃
B. CO and N₂
C. Cl₂ and N₂
D. SO₂ and N₂

Correct Answer: A

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Question 2 View Details
Nickel is used in the hydrogenation of alkenes because it
A. increases the yield of the product
Correct B. lowers the activation energy of the reaction
C. makes the reaction more exothermic
D. prevents a reverse reaction from occurring

Correct Answer: B

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Question 3 View Details
Aluminum is extracted by
Correct A. electrolysis of the purified ore
B. froth flotation of the smelted ore
C. reduction of the ore with coke in a furnace
D. roasting the ore in excess supply of air

Correct Answer: A

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Question 4 View Details
Which of the following gases is used in fire extinguishers?
Correct A. Carbon (IV) oxide
B. Nitrogen (IV) oxide
C. Carbon (II) oxide
D. Sulphur (IV) oxide

Correct Answer: A

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Question 5 View Details
Both Na⁺ and K⁺ have
A. tendency to give electrons
Correct B. positive reduction potential
C. tendency to accept electrons
D. negative oxidation potential

Correct Answer: B

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Question 6 View Details
If a gas occupies a volume of 400 cm³ at a temperature of 400 K and a pressure of 1 atm, at what temperature and pressure would its volume be 200 cm³?
A. 800 K and 1 atm
Correct B. 800 K and 0.5 atm
C. 200 K and 1 atm
D. 200 K and 0.5 atm

Correct Answer: B

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Question 7 View Details
The nucleus of a hydrogen atom consists of
Correct A. one proton only
B. one proton and one neutron
C. one neutron only
D. one electron only

Correct Answer: A

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Question 8 View Details
If acidified K₂Cr₂O₇ acts as an oxidizing agent, the colour changes from
A. orange to red
B. yellow to green
Correct C. orange to green
D. yellow to red

Correct Answer: C

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Question 9 View Details
Which of the following elements is a metalloid?
A. aluminium
Correct B. selenium
C. phosphorus
D. sodium

Correct Answer: B

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Question 10 View Details
Iodine could be separated from a mixture of iodine and calcium chloride by
A. evaporation
Correct B. sublimation
C. fractional distillation
D. fractional crystallization

Correct Answer: B

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Question 11 View Details
Sodium chloride is used in the following processes except
A. treatment of water
B. manufacturing of chloride
C. preservation of food
Correct D. separation of soap glycerol

Correct Answer: D

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Question 12 View Details
Which of the following bonds is not an intermolecular force?
A. hydrogen bond
B. van der Waal's
C. dipole-dipole
Correct D. metallic bond

Correct Answer: D

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Question 13 View Details
All the following compounds are ionic except
A. AgCl
B. KNO₃
Correct C. NO₂
D. (NH₄)₂CO₃

Correct Answer: C

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Question 14 View Details
The metal carbonate that would not decompose when heated strongly is
A. Al₂CO₃
B. CaCO₃
C. MgCO₃
Correct D. Na₂CO₃

Correct Answer: D

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Question 15 View Details
In the use of a universal indicator, red colour is an indication that the substance is a
Correct A. concentrated acid
B. concentrated alkali
C. dilute acid
D. dilute base

Correct Answer: A

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Question 16 View Details
Which of the following oxides would form two different types of acids when dissolved in water?
A. CO₂
Correct B. NO₂
C. SO₂
D. SO₃

Correct Answer: B

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Question 17 View Details
Ethanol could be prepared in the laboratory by
A. reduction of ethanoic acid
B. oxidation of primary alkanol
C. oxidation of alkenes
Correct D. hydration of ethene

Correct Answer: D

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Question 18 View Details
Alkali metals are good conductors of heat and electricity because they
Correct A. contain delocalized electrons
B. are found in the d-block
C. have vibrating ions
D. are all metals

Correct Answer: A

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Question 19 View Details
In a chemical reaction, ΔH is positive when
Correct A. ΔH_product > ΔH_reactants
B. ΔH_product < ΔH_reactants
C. ΔH_product = ΔH_reactants
D. ΔH_product = 0

Correct Answer: A

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Question 20 View Details
How many pi-bond(s) is/are present in propene?
A. three
B. six
C. two
Correct D. one

Correct Answer: D

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Question 21 View Details
Which of the following compounds would readily undergo addition reaction?
A. ethane
Correct B. butene
C. ethanol
D. benzene

Correct Answer: B

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Question 22 View Details
The number of moles of KOH present in 200 cm³ of 5.6 g dm⁻³ solution is [KOH=56 g mol⁻¹]
A. 0.01
B. 0.12
Correct C. 0.02
D. 0.01

Correct Answer: C

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Question 23 View Details
A covalent hydride which does not exist as a gas at room temperature is
Correct A. H₂O
B. BH₃
C. HCl
D. H₂S

Correct Answer: A

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Question 24 View Details
In the electrolysis of dilute hydrochloric acid at the anode,
A. oxygen gas is given off
B. hydrogen gas is given off
Correct C. chlorine gas is given off
D. hydrogen chloride gas is given off

Correct Answer: C

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Question 25 View Details
In which of the following arrangements are the ions arranged in decreasing order of ionic size?
Correct A. F, Na⁺, Mg²⁺, Al³⁺
B. Na⁺, Mg²⁺, Al³⁺, F⁻
C. Al³⁺, Na⁺, Mg²⁺, F⁻
D. Al³⁺, Mg²⁺, Na⁺, F

Correct Answer: A

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