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POST UTME BELLS UNIVERSITY 2025 Chemistry | Objective

Are you preparing for POST UTME BELLS UNIVERSITY 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

A 2.50 g sample of a compound containing only carbon and hydrogen is burned in a combustion calorimeter. The mass of CO2 produced is 1.25 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 2

The rate cons\tant for the decomposition of N2O5 at 500 K is 1.5 × 10^\( -3 \) s^\( -1 \). What is the half-life of the reaction?

A. 1.5 × 10^3 s

Correct B. 1.5 × 10^4 s

C. 1.5 × 10^5 s

D. 1.5 × 10^6 s

Correct Answer: B

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Question 3

A 25.0 mL sample of 0.100 M NaOH is mixed with 25.0 mL of 0.100 M HCl. What is the pH of the resulting solution?

A. 7.00

Correct B. 7.50

C. 8.00

D. 9.00

Correct Answer: B

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Question 4

The diagram below shows a titration setup. What is the purpose of the burette?

Correct A. To measure the volume of the solution

B. To measure the pH of the solution

C. To measure the temperature of the solution

D. To measure the density of the solution

Correct Answer: A

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Question 5

The diagram below shows a circuit. What is the purpose of the resistor?

Correct A. To reduce the current flowing through the circuit

B. To increase the voltage of the circuit

C. To decrease the resis\tance of the circuit

D. To increase the power of the circuit

Correct Answer: A

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Question 6

A polymer is formed by the condensation reaction between two monomers, A and B. The molecular weight of the polymer is 100,000 g/mol. If the molecular weight of monomer A is 50,000 g/mol and that of monomer B is 30,000 g/mol, what is the ratio of the number of moles of monomer A to the number of moles of monomer B in the polymer?

A. 1:1

B. 1:2

Correct C. 2:1

D. 3:2

Correct Answer: C

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Question 7

The reaction between sodium hydroxide (NaOH) and hydrochloric acid (HCl) is as follows: NaOH + HCl → NaCl + H2O. If 100 mL of 0.5 M NaOH is mixed with 100 mL of 0.5 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 8

A solution contains 1.0 g of glu\cose (C6H12O6) per 100 mL of solution. What is the molarity of the solution?

A. 0.1 M

B. 0.5 M

Correct C. 1.0 M

D. 2.0 M

Correct Answer: C

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Question 9

A 10% solution of acetic acid (CH3COOH) is mixed with a 10% solution of sodium hydroxide (NaOH). If 100 mL of the acetic acid solution is mixed with 100 mL of the sodium hydroxide solution, what is the pH of the resulting solution?

A. 7

Correct B. 8

C. 9

D. 10

Correct Answer: B

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Question 10

A 1.0 M solution of sodium chloride (NaCl) is mixed with a 1.0 M solution of hydrochloric acid (HCl). If 100 mL of the sodium chloride solution is mixed with 100 mL of the hydrochloric acid solution, 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 11

A 1.0 M solution of AgNO3 is mixed with a 1.0 M solution of NaCl. If the reaction is allowed to go to completion, what is the concentration of AgCl that will precipitate out of the solution?

Correct A. 0.5 M

B. 1.0 M

C. 1.5 M

D. 2.0 M

Correct Answer: A

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Question 12

A solution of HCl is added to a solution of NaOH. If the initial concentration of HCl is 0.5 M and the initial concentration of NaOH is 0.2 M, what is the pH of the resulting solution after the reaction is complete?

A. 1

B. 2

Correct C. 3

D. 4

Correct Answer: C

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Question 13

A 1.0 M solution of FeCl3 is mixed with a 1.0 M solution of NaOH. If the reaction is allowed to go to completion, what is the concentration of Fe(OH)3 that will precipitate out of the solution?

A. 0.5 M

Correct B. 1.0 M

C. 1.5 M

D. 2.0 M

Correct Answer: B

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Question 14

A solution of H2SO4 is added to a solution of BaCl2. If the initial concentration of H2SO4 is 0.5 M and the initial concentration of BaCl2 is 0.2 M, what is the pH of the resulting solution after the reaction is complete?

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 15

A 1.0 M solution of CuSO4 is mixed with a 1.0 M solution of NaOH. If the reaction is allowed to go to completion, what is the concentration of Cu(OH)2 that will precipitate out of the solution?

A. 0.5 M

Correct B. 1.0 M

C. 1.5 M

D. 2.0 M

Correct Answer: B

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Question 16

Determine the s\tandard enthalpy of formation of cyclohexane (C6H12) from the s\tandard enthalpies of formation of its constituent atoms.

A. -123.0 kJ/mol

B. -124.5 kJ/mol

Correct C. -125.0 kJ/mol

D. -126.0 kJ/mol

Correct Answer: C

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Question 17

A polymer is synthesized from a monomer with the following structure: CH2=CH-CH2-CH3. What is the repeating unit of the polymer?

Correct A. -CH2-CH2-CH2-CH2-

B. -CH2-CH2-CH2-CH3

C. -CH2-CH2-CH2-CH2-CH2-

D. -CH2-CH2-CH2-CH2-CH3

Correct Answer: A

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Question 18

A solution of 0.100 M NaOH is mixed with a solution of 0.100 M HCl. What is the pH of the resulting solution?

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 19

A sample of air contains 21.0% O2, 78.0% N2, and 1.0% Ar by volume. What is the partial pressure of O2 at a total pressure of 1.00 atm?

Correct A. 0.210 atm

B. 0.2100 atm

C. 0.21000 atm

D. 0.210000 atm

Correct Answer: A

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Question 20

A diagram of a titration setup is shown below. 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 21

The reaction of zinc metal with copper(II) sulfate solution is represented by the equation: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s). If 2.5 g of zinc metal is added to 50 mL of 0.1 M copper(II) sulfate solution, what is the limiting reac\tant?

A. Zn(s)

Correct B. CuSO4(aq)

C. ZnSO4(aq)

D. Cu(s)

Correct Answer: B

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Question 22

A 2.5 M solution of sodium hydroxide is prepared by dissolving 25 g of sodium hydroxide in 100 mL of water. What is the concentration of the solution in moles per liter?

Correct A. 2.5 M

B. 5.0 M

C. 10.0 M

D. 12.5 M

Correct Answer: A

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Question 23

The half-life of a radioactive subs\tance is 5 years. If 100 g of the subs\tance is initially present, what is the amount of the subs\tance remaining after 10 years?

A. 50 g

B. 25 g

Correct C. 12.5 g

D. 6.25 g

Correct Answer: C

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Question 24

A 2.0 M solution of hydrochloric acid is prepared by dissolving 20 g of hydrochloric acid in 100 mL of water. What is the concentration of the solution in moles per liter?

Correct A. 2.0 M

B. 4.0 M

C. 6.0 M

D. 8.0 M

Correct Answer: A

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Question 25

The reaction of hydrogen gas with oxygen gas is represented by the equation: 2H2(g) + O2(g) → 2H2O(l). If 2.0 L of hydrogen gas is added to 1.0 L of oxygen gas, what is the limiting reac\tant?

A. H2(g)

Correct B. O2(g)

C. H2O(l)

D. None of the above

Correct Answer: B

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