WAEC 2024 Chemistry | Objective

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Question 1 View Details
Which of the following gases could be collected by downward displacement of air?
A. Chlorine
Correct B. Hydrogen
C. Hydrogen chloride
D. Sulphur (IV) oxide

Correct Answer: B

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Question 2 View Details
Which of the following substances has the lowest boiling point?
A. Aqueous sodium chloride
Correct B. Ethanol.
C. Tetrachloromethane
D. Water

Correct Answer: B

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Question 3 View Details
The branch of science that deals with the nature and properties of substances and how one substance can be converted to another is known as
A. biology.
Correct B. chemistry.
C. geography.
D. physics.

Correct Answer: B

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Question 4 View Details
The electron configuration \( 1 s^{2} 2 s^{2} 2 p_{x}^{2} \) contravenes the
Correct A. Pauli's exclusion principle.
B. Aufbau's principle.
C. Octet rule.
D. Hund's rule.

Correct Answer: A

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Question 5 View Details
The oxidation number of chromium in \( \mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7} \) is
A. +2.
Correct B. +6.
C. +7.
D. +12.

Correct Answer: B

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Question 6 View Details
The most important ore of aluminium is
Correct A. bauxite.
B. haematite.
C. magnetite.
D. monazite.

Correct Answer: A

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Question 7 View Details
Bases normally
A. are corrosive
B. turn litmus paper from blue to red.
Correct C. turn litmus paper from red to blue.
D. are non-metal oxides.

Correct Answer: C

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Question 8 View Details
The product of the reaction between ethanol and excess acidified \( \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7} \) is
A. \( \mathrm{CH}_{2}=\mathrm{CH}_{2} \)
B. \( \mathrm{CH}_{3} \mathrm{OCH}_{3} \)
Correct C. CH\( { }_{3} \mathrm{COOH} \)
D. \( \mathrm{CH}_{3} \mathrm{CH}_{3} \)

Correct Answer: C

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Question 9 View Details
The product formed when concentrated sodium chloride solution is electrolysed using carbon electrodes is
A. chloride water.
Correct B. hydrochloric acid.
C. sodium hydroxide.
D. sodium oxochlorate (I).

Correct Answer: B

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Question 10 View Details
Which of the following statements about ammonium salt is correct? It
A. dissolves in water to form solution of \( pH>1 \).
Correct B. dissolves in water to form solution of \( pH<7 \).
C. does not decompose on heating.
D. is insoluble in water.

Correct Answer: B

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Question 11 View Details
Ethanedioic acid is an organic solid that can be purified by
A. decantation.
B. distillation.
Correct C. crystallization.
D. filtration.

Correct Answer: C

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Question 12 View Details
Which of the following functional groups is present in alkanoic acid?
Correct A. -COOH
B. -OH
C. -COOR
D. CHO

Correct Answer: A

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Question 13 View Details
In ethanol, the attractive forces between adjacent molecules are
A. covalent bonds only.
B. hydrogen bonds only.
Correct C. hydrogen bonds and van der Waal's forces.
D. van der Waal's forces only.

Correct Answer: C

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Question 14 View Details
At 25 °C, the saturated solution of a salt in water was found to contain 0.24 \( g \) of the salt in \( 100 cm^{3} \). What is the solubility of the salt in \( \mathrm{gdm}^{-3} \) ?
A. 0.024
Correct B. 0.240
C. 2.40
D. 24.0

Correct Answer: B

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Question 15 View Details
The reaction represented by the equation: \( \mathrm{Ni}_{(\mathrm{aq})}^{2+}+\mathrm{Fe}_{(\mathrm{s})} \longrightarrow \mathrm{Ni}_{(\mathrm{s})}+\mathrm{Fe}_{(\mathrm{aq})}^{2+} \) is a redox reaction because
A. \( \mathrm{Ni}^{2+} \) ions are oxidized and Fe acts as an oxidizing agent.
B. ions are oxidized and Fe acts as a reducing agent.
Correct C. \( \mathrm{Ni}^{2+} \) ions are reduced and Fe acts as an oxidizing agent.
D. Ni ions are reduced and Fe acts as a reducing agent.

Correct Answer: C

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Question 16 View Details
Which of the following statements describes transition elements? They
A. are very reactive.
B. have low melting points.
Correct C. possess variable oxidation state.
D. form colourless salts.

Correct Answer: C

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Question 17 View Details
Aluminium is suitable for making alloys for aircraft construction because it
A. is hard and brittle.
Correct B. is light and very resistant to corrosion.
C. has high density and also a non-conductor of electricity.
D. is amphoteric and allotropic.

Correct Answer: B

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Question 18 View Details
Which of the following arrangements of elements is in order of increasing ionization energy?
A. Si, Al, S, P
B. S, P, Si, Al
Correct C. Al, Si, P, S
D. P, Si, S, Al

Correct Answer: C

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Question 19 View Details
Consider the reaction represented by the equation: \[ \mathrm{C}_{3} \mathrm{H}_{8}+5 \mathrm{O}_{2(g)} \longrightarrow 3 \mathrm{CO}_{2(g)}+6 \mathrm{H}_{2} \mathrm{O}_{(l)} . \] If 0.1 mole of \( \mathrm{C}_{3} \mathrm{H}_{8(g)} \) was completely burnt, what volume of \( \mathrm{CO}_{2(g)} \) would be produced at \( s t p \) ? [volume at \( s t p=22.4 d m^{-3} m o l^{-1} \) ].
A. \( 6.72 d m^{3} \)
Correct B. \( 2.24 \mathrm{dm}^{3} \)
C. \( 0.30 d m^{3} \)
D. \( 0.10 d m^{3} \)

Correct Answer: B

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Question 20 View Details
Naturally occurring Boron is made up of \( 19.9 \%{ }^{10} \mathrm{B} \) and \( 80.1 \%{ }^{11} \mathrm{B} \). The relative atomic mass of Boron is
A. 21.0.
Correct B. 10.8.
C. 10.5.
D. 10.0.

Correct Answer: B

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Question 21 View Details
The number of shared pair of electrons in a molecule of methane is
A. 2.
Correct B. 4.
C. 6.
D. 8.

Correct Answer: B

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Question 22 View Details
Isotopes of the same element have similar chemical properties because they have the same number of
A. nuclides.
Correct B. protons.
C. neutrons.
D. atoms.

Correct Answer: B

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Question 23 View Details
Which of the following household liquids would be effective in treating someone with too much acid in the stomach?
A. Strong salt solution with \( \,pH 7: 0 \,\mathrm{~B} \).
B. Tomato juice with \( pH 4.1 \)
Correct C. Milk of magnesia with pH 10.5
D. Black coffee with pH 5.0

Correct Answer: C

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Question 24 View Details
The percentage by mass of oxygen in \( \mathrm{MgSO}_{4} .7 \mathrm{H}_{2} \mathrm{O} \) is \( [\mathrm{Mr}=246] \).
A. 26.0 \%.
Correct B. 45.5 \%.
C. 71.5 \%.
D. 84.0 \%.

Correct Answer: B

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Question 25 View Details
Catalysts alter reaction rates by
Correct A. providing an alternative reaction pathway.
B. lowering the energy of reaction.
C. increasing the surface area of reactants.
D. aligning the reactant molecules properly.

Correct Answer: A

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