POST UTME OSUSTECH 2025 Chemistry | Objective

Are you preparing for POST UTME OSUSTECH 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.

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Question 1
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, and ΔHf(C(s)) = 0 kJ/mol.
Correct A. -1206.60 kJ/mol
B. -1206.19 kJ/mol
C. -1206.79 kJ/mol
D. -1206.99 kJ/mol

Correct Answer: A

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Question 2
A metal (M) reacts with chlorine gas to form a white solid. The reaction is highly exothermic, relea\sing 22.5 kJ of heat per mole of M. If 2.5 g of M reacts with 1.5 g of Cl2, what is the percentage yield of the reaction?
Correct A. 75%
B. 80%
C. 85%
D. 90%

Correct Answer: A

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Question 3
The diagram below shows the periodic table. Which element is a noble gas?
A. He
Correct B. Ne
C. Ar
D. Kr

Correct Answer: B

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Question 4
A solution of 0.1 M NaOH is mixed with a solution of 0.1 M HCl. What is the pH of the resulting solution?
Correct A. 7
B. 8
C. 9
D. 10

Correct Answer: A

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Question 5
The diagram below shows a titration setup. What is the purpose of the burette?
Correct A. To measure the volume of the titrant
B. To measure the volume of the analyte
C. To mix the titrant and analyte
D. To measure the pH of the solution

Correct Answer: A

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Question 6
A polymer chain consists of 100 monomers, each with a molecular weight of 100 g/mol. If the polymer chain has a degree of polymerization of 50, what is the number-average molecular weight of the polymer?
A. 100 g/mol
Correct B. 200 g/mol
C. 500 g/mol
D. 1000 g/mol

Correct Answer: B

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Question 7
A solution of 2.0 g of NaCl in 100 mL of water has a boiling point elevation of 0.50°C. What is the molar mass of NaCl?
Correct A. 58.5 g/mol
B. 74.5 g/mol
C. 108.5 g/mol
D. 142.5 g/mol

Correct Answer: A

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Question 8
A sample of 1.0 g of an unknown hydrocarbon is burned in a bomb calorimeter, relea\sing 12.5 kJ of heat. What is the molar mass of the hydrocarbon?
A. 30 g/mol
B. 40 g/mol
Correct C. 50 g/mol
D. 60 g/mol

Correct Answer: C

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Question 9
A solution of 1.0 M NaOH is mixed with a solution of 1.0 M HCl. What is the pH of the resulting solution?
A. 1.0
B. 2.0
C. 3.0
Correct D. 4.0

Correct Answer: D

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Question 10
A gas at 25°C and 1 atm is compressed to 2 atm. What is the new volume of the gas?
Correct A. 1/2 V
B. 1/3 V
C. 2/3 V
D. V

Correct Answer: A

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Question 11
The reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH) is a classic example of a neutralization reaction. Write the balanced chemical equation for this reaction, including the state of each subs\tance.
Correct A. HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
B. HCl(aq) + NaOH(aq) → NaCl(s) + H2O(l)
C. HCl(g) + NaOH(aq) → NaCl(aq) + H2O(g)
D. HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(g)

Correct Answer: A

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Question 12
A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the number of moles of HCl in the sample.
Correct A. 0.0025
B. 0.005
C. 0.0075
D. 0.01

Correct Answer: A

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Question 13
The following diagram shows a titration setup. Identify the subs\tance being titrated.
A. HCl
Correct B. NaOH
C. H2SO4
D. NaCl

Correct Answer: B

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Question 14
A 2.00 g sample of an unknown hydrocarbon is burned in a combustion reaction. The products are 2.00 g of CO2 and 1.00 g of H2O. Calculate the empirical formula of the hydrocarbon.
Correct A. CH2
B. C2H4
C. C3H6
D. C4H8

Correct Answer: A

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Question 15
The following diagram shows a polymerization reaction. Identify the type of polymerization reaction.
A. Addition polymerization
Correct B. Condensation polymerization
C. Ring-opening polymerization
D. Step-growth polymerization

Correct Answer: B

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Question 16
The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of combustion of 2.5 g of C(s) at 298 K.
A. -981.25 kJ
Correct B. -981.375 kJ
C. -981.5 kJ
D. -981.625 kJ

Correct Answer: B

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Question 17
A 2.5 M solution of NaOH is prepared by dissolving 12.5 g of NaOH in 1 L of water. Calculate the molarity of the solution.
Correct A. 2.5 M
B. 2.5 M
C. 5.0 M
D. 10.0 M

Correct Answer: A

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Question 18
The boiling point of a solution containing 10 g of glu\cose in 100 g of water is 100.5°C. Calculate the molality of the solution.
Correct A. 0.1 m
B. 0.2 m
C. 0.3 m
D. 0.4 m

Correct Answer: A

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Question 19
A 2.5 M solution of HCl is prepared by dissolving 12.5 g of HCl in 1 L of water. Calculate the pH of the solution.
A. 1.0
Correct B. 2.0
C. 3.0
D. 4.0

Correct Answer: B

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Question 20
The s\tandard enthalpy of formation of CO(g) is -110.5 kJ/mol. Calculate the s\tandard enthalpy of combustion of 2.5 g of C(s) at 298 K.
A. -275.625 kJ
Correct B. -275.75 kJ
C. -275.875 kJ
D. -276.0 kJ

Correct Answer: B

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Question 21
A 0.1 M solution of NaOH is mixed with a 0.1 M solution of HCl. If the initial temperature of both solutions is 25°C, what is the final temperature of the mixture after complete reaction?
A. 25°C
Correct B. 30°C
C. 35°C
D. 40°C

Correct Answer: B

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Question 22
A 2.5 L flask contains 0.2 mol of CO2 at 25°C. If 0.1 mol of O2 is added to the flask, what is the new partial pressure of CO2?
A. 0.2 atm
B. 0.3 atm
Correct C. 0.4 atm
D. 0.5 atm

Correct Answer: C

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Question 23
A 0.1 M solution of FeCl3 is mixed with a 0.1 M solution of NaOH. If the initial temperature of both solutions is 25°C, what is the final temperature of the mixture after complete reaction?
A. 25°C
B. 30°C
C. 35°C
Correct D. 40°C

Correct Answer: D

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Question 24
A 2.5 L flask contains 0.2 mol of CO2 at 25°C. If 0.1 mol of O2 is added to the flask, what is the new partial pressure of CO2?
A. 0.2 atm
B. 0.3 atm
Correct C. 0.4 atm
D. 0.5 atm

Correct Answer: C

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Question 25
A 0.1 M solution of FeCl3 is mixed with a 0.1 M solution of NaOH. If the initial temperature of both solutions is 25°C, what is the final temperature of the mixture after complete reaction?
A. 25°C
B. 30°C
C. 35°C
Correct D. 40°C

Correct Answer: D

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