POST UTME OAU 2025 Chemistry | Objective

Are you preparing for POST UTME OAU exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2025 Chemistry (Objective) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1
Determine the pH of a 0.1 M solution of HCl.
A. 1
B. 2
C. 3
Correct D. 4

Correct Answer: D

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Question 2
A 2.5 L flask contains 0.5 mol of an ideal gas at 27°C. Calculate the pressure of the gas.
A. 1.5 atm
Correct B. 2.5 atm
C. 3.5 atm
D. 4.5 atm

Correct Answer: B

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Question 3
The diagram below shows a titration setup. Identify the part labeled A.
Correct A. Burette
B. Beaker
C. Conical Flask
D. Erlenmeyer Flask

Correct Answer: A

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Question 4
A solution contains 0.2 mol of NaOH and 0.1 mol of HCl. Calculate the pH of the solution.
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 5
The diagram below shows a circuit setup. Identify the part labeled A.
Correct A. Resistor
B. Battery
C. Switch
D. Ammeter

Correct Answer: A

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Question 6
A 0.5 M solution of NaCl is prepared by dissolving 25 g of NaCl in 1000 mL of water. Calculate the number of moles of NaCl dissolved.
A. 2.5 x 10^-4 mol
Correct B. 5.0 x 10^-4 mol
C. 7.5 x 10^-4 mol
D. 1.0 x 10^-3 mol

Correct Answer: B

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Question 7
A sample of CO2 gas occupies a volume of 2.5 L at a pressure of 1.5 atm. Calculate the temperature of the gas in Kelvin.
Correct A. 45.7 K
B. 50.0 K
C. 55.0 K
D. 60.0 K

Correct Answer: A

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Question 8
A 2.0 M solution of HCl is prepared by dissolving 40 g of HCl in 1000 mL of water. Calculate the pH of the solution.
A. 1.5
Correct B. 1.7
C. 2.0
D. 2.5

Correct Answer: B

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Question 9
A 1.0 M solution of NaOH is prepared by dissolving 40 g of NaOH in 1000 mL of water. Calculate the pOH of the solution.
A. 13.0
Correct B. 14.0
C. 15.0
D. 16.0

Correct Answer: B

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Question 10
A 0.5 M solution of H2SO4 is prepared by dissolving 50 g of H2SO4 in 1000 mL of water. Calculate the number of moles of H2SO4 dissolved.
A. 2.5 x 10^-4 mol
Correct B. 5.0 x 10^-4 mol
C. 7.5 x 10^-4 mol
D. 1.0 x 10^-3 mol

Correct Answer: B

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Question 11
Determine the number of moles of $\text{O}_2$ that react with 2.50 moles of $\text{H}_2$ in the reaction $\text{H}_2 + \frac{1}{2}\text{O}_2 \rightarrow \text{H}_2\text{O}$
Correct A. 1.25
B. 2.50
C. 3.75
D. 5.00

Correct Answer: A

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Question 12
The half-life of a radioactive subs\tance is 5.00 years. If 100.0 g of the subs\tance initially exists, what is the mass remaining after 20.0 years?
Correct A. 12.5
B. 25.0
C. 50.0
D. 100.0

Correct Answer: A

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Question 13
A 2.00 M solution of $\text{HCl}$ is mixed with a 1.00 M solution of $\text{NaOH}$. What is the concentration of the resulting solution?
A. 0.50
Correct B. 1.00
C. 1.50
D. 2.00

Correct Answer: B

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Question 14
A 5.00 g sample of a metal is heated in a crucible until it reaches a temperature of 1000°C. If the specific heat capacity of the metal is 0.10 J/g°C, what is the energy required to heat the metal to 1000°C?
A. 50.0
B. 100.0
C. 150.0
Correct D. 200.0

Correct Answer: D

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Question 15
A 1.00 M solution of $\text{H}_2\text{SO}_4$ is mixed with a 2.00 M solution of $\text{BaCl}_2$. What is the concentration of the resulting solution?
A. 0.50
B. 1.00
C. 1.50
Correct D. 2.00

Correct Answer: D

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Question 16
Determine the pH of a 0.1 M solution of HCl, given that the dissociation cons\tant of HCl is 10^\( -7 \) and the dissociation cons\tant of H2O is 10^\( -14 \).
Correct A. 1
B. 2
C. 3
D. 4

Correct Answer: A

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Question 17
A sample of a gas occupies a volume of 2.5 L at a temperature of 298 K and a pressure of 1 atm. If the temperature is increased to 373 K, what is the new volume of the gas?
A. 3.2 L
Correct B. 4.0 L
C. 4.8 L
D. 5.6 L

Correct Answer: B

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Question 18
A solution contains 0.2 M NaOH and 0.1 M HCl. What is the pH of the solution after the reaction is complete?
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 19
A polymer has a molecular weight of 100,000 g/mol and a degree of polymerization of 500. What is the molar mass of the repeating unit?
A. 200 g/mol
B. 400 g/mol
Correct C. 500 g/mol
D. 600 g/mol

Correct Answer: C

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Question 20
A solution contains 0.1 M H2SO4 and 0.2 M NaOH. What is the pH of the solution after the reaction is complete?
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 21
The reaction of nitrogen dioxide with water produces nitric acid and nitric oxide. Write the balanced chemical equation for this reaction, including the states of the reac\tants and products.
A. 4NO2(g) + 2H2O(l) → 4HNO3(aq) + O2(g)
Correct B. 2NO2(g) + 2H2O(l) → 2HNO3(aq) + O2(g)
C. 4NO2(g) + 2H2O(l) → 4HNO3(aq)
D. 2NO2(g) + 2H2O(l) → 2HNO3(aq)

Correct Answer: B

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Question 22
A 2.5 g sample of a polymer is dissolved in 50 mL of a solvent. If the density of the solution is 1.2 g/mL, what is 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 23
The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of H2O(l) if the s\tandard enthalpy of formation of CO(g) is -110.5 kJ/mol and the s\tandard enthalpy of formation of H2(g) is 0 kJ/mol?
Correct A. -285.8 kJ/mol
B. -285.9 kJ/mol
C. -286.0 kJ/mol
D. -286.1 kJ/mol

Correct Answer: A

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Question 24
A 10.0 mL sample of a solution containing 0.500 M NaOH is titrated with 0.500 M HCl. What is the pH of the solution after the titration is complete?
A. 7.00
Correct B. 7.50
C. 8.00
D. 9.00

Correct Answer: B

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Question 25
A 2.0 g sample of a metal is heated in a crucible until it is completely oxidized. The mass of the crucible and the oxide is 4.2 g. What is the mass of the metal that was oxidized?
A. 1.2 g
B. 1.5 g
Correct C. 1.8 g
D. 2.0 g

Correct Answer: C

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