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POST UTME UNIOSUN 2020 Chemistry | Objective

Are you preparing for POST UTME UNIOSUN exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2020 Chemistry (Objective) questions designed to simulate the real exam environment.

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Question 1

The reaction of polyethylene with oxygen in the presence of a catalyst is an example of a

A. combustion reaction

Correct B. oxidation reaction

C. polymerization reaction

D. degradation reaction

Correct Answer: B

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Question 2

The electrolysis of water produces hydrogen gas at the cathode and oxygen gas at the anode. What is the half-reaction at the cathode?

Correct A. 2H+ + 2e- → H2

B. 2H2O → O2 + 4H+ + 4e-

C. 2H2O + 2e- → H2 + 2OH-

D. 2H+ + 2e- → H2O

Correct Answer: A

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Question 3

The rate cons\tant of a reaction is 1.5 s-1. If the initial concentration of the reac\tant is 0.5 M, what is the concentration after 2 minutes?

Correct A. 0.25 M

B. 0.50 M

C. 0.75 M

D. 1.00 M

Correct Answer: A

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Question 4

The half-life of a radioactive subs\tance is 5 years. If the initial activity is 1000 Bq, what is the activity after 10 years?

Correct A. 250 Bq

B. 500 Bq

C. 750 Bq

D. 1000 Bq

Correct Answer: A

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Question 5

The reaction of iron with oxygen in the presence of moisture is an example of a

Correct A. corrosion reaction

B. oxidation reaction

C. polymerization reaction

D. degradation reaction

Correct Answer: A

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Question 6

Calculate the s\tandard enthalpy change for the reaction: 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s). Given that ΔH°(Al2O3) = -1675 kJ/mol, ΔH°(Fe) = -13.8 kJ/mol, and ΔH°(Al) = 0 kJ/mol.

A. -1650 kJ/mol

Correct B. -1675 kJ/mol

C. -1700 kJ/mol

D. -1725 kJ/mol

Correct Answer: B

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Question 7

A 2.5 L flask contains 0.15 mol of an ideal gas at 27°C. Calculate the pressure of the gas u\sing the ideal gas law.

A. 1.1 atm

Correct B. 1.2 atm

C. 1.3 atm

D. 1.4 atm

Correct Answer: B

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Question 8

The half-life of a radioactive subs\tance is 5 years. If 100 g of the subs\tance is initially present, how much will remain after 15 years?

Correct A. 12.5 g

B. 25 g

C. 50 g

D. 100 g

Correct Answer: A

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Question 9

A 10 M solution of HCl is mixed with a 10 M solution of NaOH. Calculate 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 L flask contains 0.50 mol of CO2 at 25°C. Calculate the partial pressure of CO2 u\sing the ideal gas law.

A. 1.1 atm

Correct B. 1.2 atm

C. 1.3 atm

D. 1.4 atm

Correct Answer: B

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Question 11

A polymer is a large molecule composed of many repeated subunits called monomers. Which of the following is an example of a polymer?

A. DNA

B. Water

Correct C. Polyethylene

D. Glu\cose

Correct Answer: C

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Question 12

A solution of 0.1 M HCl is titrated with 0.1 M NaOH. What is the pH of the solution after 25 mL of NaOH has been added?

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 13

A 2.5 g sample of a subs\tance is dissolved in 50 mL of water. The resulting solution has a concentration of 0.5 M. What is the molar mass of the subs\tance?

A. 10 g/mol

Correct B. 20 g/mol

C. 30 g/mol

D. 40 g/mol

Correct Answer: B

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Question 14

A 10 mL sample of a solution containing 0.1 M CuSO4 is electrolyzed u\sing a current of 2 A for 5 minutes. What is the mass of copper deposited at the cathode?

A. 0.1 g

Correct B. 0.2 g

C. 0.3 g

D. 0.4 g

Correct Answer: B

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Question 15

A 1.5 L sample of a gas at 2 atm and 300 K is compressed to 4 atm. What is the new volume of the gas?

A. 0.5 L

B. 1 L

Correct C. 2 L

D. 3 L

Correct Answer: C

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Question 16

A metal oxide, M2O3, is formed by the reaction of a metal, M, with oxygen. If 2.5 g of M2O3 is obtained from 3.2 g of M, calculate the percentage yield of M2O3.

A. 75%

Correct B. 80%

C. 85%

D. 90%

Correct Answer: B

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Question 17

A sample of a gas at 25°C and 1 atm is compressed to 2 atm. Calculate the new volume of the gas, assuming ideal gas behavior.

A. 0.5 L

B. 1 L

Correct C. 2 L

D. 4 L

Correct Answer: C

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Question 18

A solution of 0.1 M NaCl is prepared by dissolving 5.0 g of NaCl in 100 mL of water. What is the concentration of the solution in g/L?

A. 0.5 g/L

B. 1 g/L

C. 2 g/L

Correct D. 5 g/L

Correct Answer: D

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Question 19

A 2.0 L flask contains a mixture of 1.0 M HCl and 0.5 M NaOH. What is the concentration of the resulting solution?

A. 0.5 M

B. 1 M

Correct C. 1.5 M

D. 2 M

Correct Answer: C

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Question 20

A 10.0 mL sample of a solution containing 0.1 M CuSO4 is titrated with 0.1 M NaOH. What is the volume of NaOH required to reach the equivalence point?

A. 10 mL

Correct B. 20 mL

C. 30 mL

D. 40 mL

Correct Answer: B

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Question 21

A 2.5 M solution of HCl is prepared by dissolving 25 g of HCl in 1000 mL of water. Calculate the number of moles of HCl in the solution.

A. 0.1 mol

B. 0.2 mol

Correct C. 0.25 mol

D. 0.5 mol

Correct Answer: C

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Question 22

A sample of a gas has a volume of 2.5 L at a pressure of 1.5 atm. If the pressure is increased to 3.0 atm, what is the new volume of the gas?

A. 1.5 L

Correct B. 2.0 L

C. 2.5 L

D. 3.0 L

Correct Answer: B

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Question 23

A 0.1 M solution of NaOH is prepared by dissolving 1 g of NaOH in 1000 mL of water. Calculate the pH of the solution.

A. 12

B. 13

Correct C. 14

D. 15

Correct Answer: C

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Question 24

A sample of a metal is heated in a crucible and reacts with oxygen to form a compound. The reaction is represented by the equation: 2M + O2 → 2MO. If 2.5 g of the metal is heated, what is the mass of oxygen required?

A. 1.0 g

Correct B. 1.5 g

C. 2.0 g

D. 2.5 g

Correct Answer: B

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Question 25

A 1.0 M solution of H2SO4 is prepared by dissolving 50 g of H2SO4 in 1000 mL of water. Calculate the number of moles of H2SO4 in the solution.

A. 0.05 mol

Correct B. 0.1 mol

C. 0.15 mol

D. 0.2 mol

Correct Answer: B

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