POST UTME UNIBEN 2023 Chemistry | Objective

Are you preparing for POST UTME UNIBEN exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2023 Chemistry (Objective) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1
The reaction of zinc metal with copper(II) sulfate solution is represented by the equation: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s). What is the oxidation state of copper in the product Cu(s)?
A. 0
B. +1
Correct C. -1
D. +2

Correct Answer: C

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Question 2
A solution containing 0.1 M HCl and 0.1 M NaOH is prepared. What is the pH of the solution after complete neutralization?
A. 1
Correct B. 7
C. 10
D. 14

Correct Answer: B

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Question 3
The diagram below shows a titration setup. What is the purpose of the burette?
A. To measure the volume of the solution
Correct B. To add the titrant
C. To mix the solution
D. To measure the pH

Correct Answer: B

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Question 4
The reaction of hydrogen gas with oxygen gas is represented by the equation: 2H2(g) + O2(g) → 2H2O(l). What is the oxidation state of oxygen in the product H2O(l)?
Correct A. -2
B. +1
C. +2
D. 0

Correct Answer: A

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Question 5
A solution containing 0.1 M HCl and 0.1 M NaOH is prepared. What is the concentration of the resulting solution after complete neutralization?
A. 0.1 M
Correct B. 0.05 M
C. 0.01 M
D. 0.001 M

Correct Answer: B

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Question 6
Determine the molar mass of a polymer with the repeating unit (C6H4)2(CO)2.
A. 120 g/mol
Correct B. 180 g/mol
C. 240 g/mol
D. 300 g/mol

Correct Answer: B

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Question 7
A 0.1 M solution of NaCl is mixed with 10 mL of 0.1 M AgNO3. What is the concentration of AgCl formed?
Correct A. 0.01 M
B. 0.1 M
C. 0.2 M
D. 0.5 M

Correct Answer: A

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Question 8
A 2.0 g sample of a polymer is dissolved in 100 mL of solvent. The osmotic pressure of the solution is 1.5 atm. Calculate the molar mass of the polymer.
A. 100 g/mol
B. 200 g/mol
Correct C. 500 g/mol
D. 1000 g/mol

Correct Answer: C

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Question 9
A 0.1 M solution of HCl is mixed with 10 mL of 0.1 M NaOH. What is the pH of the resulting solution?
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 10
A 2.0 g sample of a polymer is dissolved in 100 mL of solvent. The vis\cosity of the solution is 1.5 cP. Calculate the molar mass of the polymer.
A. 100 g/mol
B. 200 g/mol
Correct C. 500 g/mol
D. 1000 g/mol

Correct Answer: C

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Question 11
The atomic radius of an element in the periodic table increases down a group due to the addition of new energy levels. However, this tr\end is disrupted in the case of the noble gases. Explain the reason behind this disruption.
Correct A. The noble gases have a full outer energy level, making it difficult for them to form compounds and thus disrupting the tr\end.
B. The noble gases have a higher atomic radius due to the presence of more protons in their nucleus.
C. The noble gases have a lower atomic radius due to the presence of more electrons in their outer energy level.
D. The noble gases have a unique electronic configuration that makes them resis\tant to changes in atomic radius.

Correct Answer: A

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Question 12
A polymer is a large molecule composed of many repeated subunits called monomers. What is the primary function of a polymer in a bio\logical system?
Correct A. To provide structural support to cells and tissues.
B. To facilitate the transport of nutrients and waste products across cell membranes.
C. To regulate the activity of enzymes and other biomolecules.
D. To store genetic information in the form of DNA.

Correct Answer: A

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Question 13
A strong acid is defined as an acid that completely dissociates in water to produce hydrogen ions. What is the pH of a 0.1 M solution of hydrochloric acid (HCl)?
Correct A. 1
B. 2
C. 3
D. 4

Correct Answer: A

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Question 14
A hydrocarbon is a compound that consists only of hydrogen and carbon atoms. What is the general formula for an alkane, which is a type of hydrocarbon?
A. CnH2n
Correct B. CnH2n+2
C. CnH2n-2
D. CnH2n-1

Correct Answer: B

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Question 15
A metal is a type of element that is typically hard, shiny, and malleable. What is the primary function of a metal in a techno\logical application?
Correct A. To provide structural support and durability.
B. To facilitate the transmission of electricity.
C. To store energy in the form of batteries.
D. To regulate the activity of enzymes and other biomolecules.

Correct Answer: A

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Question 16
Determine the number of moles of oxygen gas (O2) required to completely combust 2.5 moles of propane (C3H8) according to the balanced equation: C3H8 + 5O2 → 3CO2 + 4H2O.
A. 10 moles
Correct B. 5 moles
C. 15 moles
D. 20 moles

Correct Answer: B

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Question 17
A 2.5 M solution of HCl is prepared by dissolving 12.5 g of HCl in 500 mL of water. Calculate the concentration of the solution in units of mol/L.
A. 0.1 M
Correct B. 0.5 M
C. 1.0 M
D. 2.0 M

Correct Answer: B

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Question 18
The s\tandard reduction potential of the Cu2+/Cu couple is +0.34 V. Calculate the s\tandard cell potential for a cell consisting of a Cu2+/Cu couple in the anode and a Zn2+/Zn couple in the cathode.
A. +0.10 V
B. +0.20 V
C. +0.30 V
Correct D. +0.40 V

Correct Answer: D

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Question 19
The boiling point of an organic compound is 120°C. If the compound is a mixture of 60% hexane and 40% toluene, calculate the boiling point of the mixture.
A. 110°C
B. 115°C
Correct C. 120°C
D. 125°C

Correct Answer: C

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Question 20
A 1.0 M solution of NaOH is prepared by dissolving 40 g of NaOH in 1 L of water. Calculate the pH of the solution.
A. 10
Correct B. 11
C. 12
D. 13

Correct Answer: B

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Question 21
The rate cons\tant of a first-order reaction is given by the equation: k = 2.303/t \log[A]0/[A]t. If the initial concentration of the reac\tant is 0.1 M and the concentration at time t is 0.01 M, calculate the rate cons\tant k.
A. 0.0001 s^-1
B. 0.001 s^-1
Correct C. 0.01 s^-1
D. 0.1 s^-1

Correct Answer: C

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Question 22
A solution containing 0.1 M NaOH is titrated with 0.1 M HCl. The pH of the solution at the equivalence point is 7. Calculate the pH of the solution at the half-equivalence point.
A. 3
Correct B. 4
C. 5
D. 6

Correct Answer: B

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Question 23
The diagram below shows a titration setup. Identify the part labeled A.
Correct A. Burette
B. Beaker
C. Test tube
D. Cylinder

Correct Answer: A

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Question 24
The half-life of a radioactive subs\tance is 10 years. If the initial activity is 1000 Bq, calculate the activity after 20 years.
Correct A. 100 Bq
B. 200 Bq
C. 500 Bq
D. 1000 Bq

Correct Answer: A

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Question 25
A solution containing 0.1 M NaOH is titrated with 0.1 M HCl. The pH of the solution at the equivalence point is 7. Calculate the pH of the solution at the half-equivalence point.
A. 3
Correct B. 4
C. 5
D. 6

Correct Answer: B

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