10 questions from the JAMB 2023 Chemistry paper, with answers and explanations. Tap "Show answer" under each one when you are ready.
JAMB 2023Question 1 · Acids, Bases, and Salts
When an acidic solution is diluted, what happens to its pH?
A.It depends on the specific acid
B.It decreases
C.It remains the same
D.It increases
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Answer: D. It increases
Diluting an acidic solution reduces [H+], raising (increasing) its pH toward 7.
JAMB 2023Question 2 · Atomic Structure and Chemical Bonding
Isotopes of an element have
A.The same number of protons but different numbers of neutrons.
B.The same number of neutrons and electrons
C.The same number of protons and neutrons
D.The same number of protons and electrons
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Answer: A. The same number of protons but different numbers of neutrons.
Isotopes of an element share the same number of protons but differ in their number of neutrons.
JAMB 2023Question 3 · Chemistry of Metals
What is the principal ore of iron, from which iron is extracted?
A.Calcite
B.Bauxite
C.Magnetite
D.Hematite
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Answer: D. Hematite
Haematite (Fe2O3) is the principal ore from which iron is extracted.
JAMB 2023Question 4 · Chemistry of Non-metals and Gases
A gas occupies a volume of 1.5 liters at a pressure of 2 atmospheres. If the pressure is increased to 4 atmospheres while the temperature remains constant, what will be the new volume of the gas?
A.6 liters
B.1.5 liters
C.0.75 liters
D.3 liters
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Answer: C. 0.75 liters
By Boyle's law, P1V1 = P2V2: 2x1.5 = 4xV2, so V2 = 43 = 0.75 litres.
JAMB 2023Question 5 · Electrochemistry and Redox Reactions
What is Faraday's constant?
A.6.022×1023mol−1
B.3.00×108 m/s
C.9.81ms−2
D.96,485Cmol−1
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Answer: D.96,485Cmol−1
Faraday's constant is 96,485Cmol−1 (the charge on one mole of electrons).
JAMB 2023Question 6 · Environmental and Industrial Chemistry
Which of the following methods can be used to remove temporary hardness from water?
A.Boiling
B.Filtration
C.sedimentation
D.Chlorination
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Answer: A. Boiling
Boiling removes temporary hardness by decomposing dissolved calcium/magnesium hydrogencarbonates into insoluble carbonates.
JAMB 2023Question 7 · Organic Chemistry
What is the chemical structure of soap and detergent molecules?
A.Hydrophilic head and hydrophobic tail
B.Hydrophilic head and hydrophilic tail
C.Hydrophobic head and hydrophobic tail
D.Hydrophilic tail and hydrophobic head
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Answer: A. Hydrophilic head and hydrophobic tail
Soap and detergent molecules have a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) hydrocarbon tail.
JAMB 2023Question 8 · Organic Chemistry
Which functional group is present in alkanals?
A.Carbonyl group (C=O)
B.Hydroxyl group (-OH)
C.Alkyl group (-R)
D.Carboxyl group (-COOH)
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Answer: A. Carbonyl group (C=O)
Alkanals (aldehydes) contain the carbonyl (C=O) functional group.
JAMB 2023Question 9 · Physical Chemistry
Which of the following reactions would be expected to have the highest entropy change?
A.Liquid → Gas
B.Solid → Liquid
C.Gas → Liquid
D.Gas → Solid
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Answer: A. Liquid → Gas
A liquid turning into a gas involves a large increase in disorder (particles becoming widely spaced and freely moving), giving the highest entropy change among the listed changes.
JAMB 2023Question 10 · Physical Chemistry
Which of the following mixtures is an example of a colloid?
A.Milk
B.Orange juice
C.Saltwater
D.Sugar dissolved in water
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Answer: A. Milk
Milk is a colloid, consisting of fat globules and proteins dispersed in a water-based liquid.
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