POST UTME RSU 2025 Chemistry | Objective

Are you preparing for POST UTME RSU 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
A 0.1 M solution of NaCl is prepared by dissolving 0.1 g of NaCl in 100 mL of water. What is the concentration of Na+ ions in the solution?
A. 0.1 M
Correct B. 0.05 M
C. 0.01 M
D. 0.005 M

Correct Answer: B

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Question 2
A 2.0 g sample of a compound containing only carbon and hydrogen is analyzed by combustion. The amount of CO2 produced is 1.2 g and the amount of H2O produced is 0.8 g. What is the empirical formula of the compound?
Correct A. CH2
B. C2H4
C. C3H6
D. C4H8

Correct Answer: A

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Question 3
A 1.0 M solution of HCl is prepared by dissolving 1.0 g of HCl in 100 mL of water. What is the pH of the solution?
Correct A. 1
B. 2
C. 3
D. 4

Correct Answer: A

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Question 4
A 0.1 M solution of NaOH is prepared by dissolving 0.1 g of NaOH in 100 mL of water. What is the concentration of OH- ions in the solution?
Correct A. 0.1 M
B. 0.05 M
C. 0.01 M
D. 0.005 M

Correct Answer: A

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Question 5
A 2.0 g sample of a compound containing only carbon and hydrogen is analyzed by combustion. The amount of CO2 produced is 1.2 g and the amount of H2O produced is 0.8 g. What is the molar mass of the compound?
A. 30 g/mol
Correct B. 60 g/mol
C. 90 g/mol
D. 120 g/mol

Correct Answer: B

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Question 6
Determine the number of moles of oxygen gas (O2) produced when 2.5 moles of hydrogen peroxide (H2O2) decompose according to the equation: 2H2O2(l) → 2H2O(l) + O2(g).
Correct A. 1.25 moles
B. 2.5 moles
C. 3.75 moles
D. 5 moles

Correct Answer: A

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Question 7
A sample of nitrogen gas (N2) at 25°C and 1 atm is allowed to expand to 2 atm. What is the new volume of the gas, assuming ideal gas behavior?
A. 50 L
B. 100 L
Correct C. 200 L
D. 400 L

Correct Answer: C

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Question 8
A 2.5 M solution of sulfuric acid (H2SO4) is prepared by dissolving 2.5 g of H2SO4 in 100 mL of water. What is the concentration of the solution in g/L?
A. 0.025 g/L
B. 0.25 g/L
Correct C. 2.5 g/L
D. 25 g/L

Correct Answer: C

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Question 9
A 5.0 g sample of sodium chloride (NaCl) is dissolved in 100 mL of water to prepare a solution. What is the concentration of the solution in g/L?
A. 0.05 g/L
B. 0.5 g/L
Correct C. 5 g/L
D. 50 g/L

Correct Answer: C

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Question 10
A 1.0 M solution of sodium hydroxide (NaOH) is prepared by dissolving 4.0 g of NaOH in 100 mL of water. What is the concentration of the solution in g/L?
A. 0.04 g/L
B. 0.4 g/L
Correct C. 4 g/L
D. 40 g/L

Correct Answer: C

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Question 11
Determine the s\tandard enthalpy of formation of CaCO3(s) from the following data: ΔHf(CaO(s)) = -635.09 kJ/mol, ΔHf(CO2(g)) = -393.51 kJ/mol. The reaction is CaO(s) + CO2(g) → CaCO3(s).
Correct A. -1781.60 kJ/mol
B. -1781.60 kJ/mol
C. -1781.60 kJ/mol
D. -1781.60 kJ/mol

Correct Answer: A

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Question 12
A 2.50 M solution of HCl is titrated with a 1.00 M solution of NaOH. Calculate the pH of the solution after 25.0 mL of NaOH has been added.
Correct A. 2.00
B. 2.00
C. 2.00
D. 2.00

Correct Answer: A

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Question 13
The diagram below shows a titration curve for the reaction between HCl and NaOH. Identify the pH at point A.
A. 1.00
Correct B. 2.00
C. 3.00
D. 4.00

Correct Answer: B

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Question 14
A sample of benzene (C6H6) has a mass of 25.0 g. Calculate the number of moles of benzene present.
Correct A. 0.250 mol
B. 0.250 mol
C. 0.250 mol
D. 0.250 mol

Correct Answer: A

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Question 15
The diagram below shows a setup for the extraction of a metal from its ore. Identify the purpose of the beaker labeled B.
A. To dissolve the metal oxide
Correct B. To dissolve the metal oxide
C. To dissolve the metal oxide
D. To dissolve the metal oxide

Correct Answer: B

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Question 16
The atomic radius of an element decreases across a period in the periodic table. Which of the following is a correct explanation for this tr\end?
Correct A. The atomic radius decreases due to the increase in effective nuclear charge.
B. The atomic radius decreases due to the decrease in atomic mass.
C. The atomic radius decreases due to the increase in electron-electron repulsion.
D. The atomic radius decreases due to the decrease in atomic size.

Correct Answer: A

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Question 17
A solution of 0.1 M NaCl is prepared by dissolving 6.0 g of NaCl in 100 mL of water. What is the concentration of Cl- ions in the solution?
A. 0.05 M
Correct B. 0.1 M
C. 0.2 M
D. 0.5 M

Correct Answer: B

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Question 18
A sample of 2.0 g of a hydrocarbon is burned in a combustion apparatus. The volume of CO2 produced is 2.5 L at STP. What is the empirical formula of the hydrocarbon?
A. CH4
Correct B. C2H6
C. C3H8
D. C4H10

Correct Answer: B

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Question 19
A 0.1 M solution of HCl is prepared by dissolving 3.0 g of HCl in 100 mL of water. What is the pH of the solution?
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 20
A sample of 1.0 g of a non-metallic oxide is heated in a crucible. The mass of the oxide decreases by 0.5 g. What is the percentage decrease in mass?
A. 25%
Correct B. 30%
C. 35%
D. 40%

Correct Answer: B

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Question 21
The solubility of a subs\tance is defined as the maximum amount of solute that can dissolve in a given amount of solvent at a particular temperature. What is the term for the minimum amount of solvent required to dissolve a given amount of solute at a particular temperature?
A. Solubility limit
B. Solubility product
C. Solubility equilibrium
Correct D. Solubility minimum

Correct Answer: D

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Question 22
A 0.1 M solution of NaCl is prepared by dissolving 6.0 g of NaCl in 100 mL of water. What is the concentration of the solution in g/L?
A. 0.6 g/L
Correct B. 6.0 g/L
C. 60 g/L
D. 600 g/L

Correct Answer: B

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Question 23
A metal M reacts with oxygen to form a basic oxide MO. The reaction is as follows: M + O2 → MO. If 2.5 g of M reacts with 10.0 g of O2 to form 3.0 g of MO, what is the percentage yield of the reaction?
A. 80%
B. 90%
Correct C. 95%
D. 98%

Correct Answer: C

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Question 24
A solution of HCl is prepared by dissolving 25.0 g of HCl in 100 mL of water. What is the concentration of the solution in M?
Correct A. 0.25 M
B. 0.5 M
C. 1.0 M
D. 2.0 M

Correct Answer: A

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Question 25
A 0.1 M solution of NaOH is prepared by dissolving 2.0 g of NaOH in 100 mL of water. What is the concentration of the solution in g/L?
Correct A. 2.0 g/L
B. 20 g/L
C. 200 g/L
D. 2000 g/L

Correct Answer: A

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