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POST UTME UNN 2022 Chemistry | Objective

Are you preparing for POST UTME UNN exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2022 Chemistry (Objective) questions designed to simulate the real exam environment.

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Question 1

The atomic radius of a metal atom is 200 pm. If the metal atom has a valency of 2, what is the expected value of the atomic radius of its monovalent ion?

Correct A. 180 pm

B. 220 pm

C. 240 pm

D. 260 pm

Correct Answer: A

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Question 2

A sample of an ideal gas occupies a volume of 2.5 L at a pressure of 1.5 atm. What is the expected volume of the gas at a pressure of 3.0 atm, assuming the temperature remains cons\tant?

A. 1.67 L

Correct B. 2.33 L

C. 3.33 L

D. 4.67 L

Correct Answer: B

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Question 3

The reaction of an alkene with a strong acid results in the formation of a tertiary alcohol. What is the expected product of the reaction?

Correct A. CH₃C(OH)(CH₃)₂

B. CH₃CH(OH)CH₃

C. CH₃C(OH)CH₂CH₃

D. CH₃CH₂C(OH)CH₃

Correct Answer: A

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Question 4

A polymer has a molecular weight of 50,000 g/mol. If the polymer has a degree of polymerization of 500, what is the expected molecular weight of the monomer?

A. 100 g/mol

Correct B. 500 g/mol

C. 1000 g/mol

D. 5000 g/mol

Correct Answer: B

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Question 5

A metal has a density of 10 g/cm³. If the metal has a volume of 2 cm³, what is the expected mass of the metal?

A. 20 g

Correct B. 30 g

C. 40 g

D. 50 g

Correct Answer: B

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Question 6

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of CaCO3(s) u\sing the following reaction: CaO(s) + CO2(g) → CaCO3(s).

A. -1206.5 kJ/mol

B. -1206.5 kJ/mol

C. -1206.5 kJ/mol

Correct D. -1206.5 kJ/mol

Correct Answer: D

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Question 7

A 2.50 g sample of a non-metallic oxide of nitrogen is dissolved in water to give a solution with a pH of 7.00. What is the molar mass of the oxide?

A. 60.0 g/mol

B. 60.0 g/mol

C. 60.0 g/mol

Correct D. 60.0 g/mol

Correct Answer: D

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Question 8

A 1.00 L sample of a gas at 25°C and 1.00 atm is collected over water at 25°C. The vapor pressure of water at 25°C is 23.8 mmHg. What is the partial pressure of the gas?

A. 0.976 atm

B. 0.976 atm

C. 0.976 atm

Correct D. 0.976 atm

Correct Answer: D

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Question 9

A 10.0 mL sample of a 0.100 M solution of NaOH is mixed with 10.0 mL of a 0.100 M solution of HCl. What is the pH of the resulting solution?

A. 7.00

B. 7.00

C. 7.00

Correct D. 7.00

Correct Answer: D

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Question 10

A 5.00 g sample of a non-metallic oxide of nitrogen is dissolved in water to give a solution with a pH of 7.00. What is the molar mass of the oxide?

A. 60.0 g/mol

B. 60.0 g/mol

C. 60.0 g/mol

Correct D. 60.0 g/mol

Correct Answer: D

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Question 11

Determine the number of moles of oxygen gas (O2) produced at STP when 2.5 moles of hydrogen gas (H2) react with oxygen gas according to the equation: 2H2 + O2 → 2H2O.

A. 1.25 moles

B. 2.5 moles

Correct C. 3.75 moles

D. 5 moles

Correct Answer: C

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Question 12

A 2.5 L flask contains 0.5 mol of an ideal gas at 300 K. If the gas is heated to 400 K at cons\tant volume, what is the new pressure?

A. 1.5 atm

B. 2.5 atm

Correct C. 3.5 atm

D. 4.5 atm

Correct Answer: C

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Question 13

A polymer has a degree of polymerization (n) of 1000. If the molecular weight of the repeating unit is 100 g/mol, what is the molecular weight of the polymer?

Correct A. 100,000 g/mol

B. 200,000 g/mol

C. 300,000 g/mol

D. 400,000 g/mol

Correct Answer: A

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Question 14

A 10 g sample of a subs\tance is burned in a bomb calorimeter, relea\sing 2500 J of heat. If the heat capacity of the calorimeter is 1000 J/K, what is the change in internal energy (ΔU) of the subs\tance?

Correct A. -2500 J

B. -2000 J

C. -1500 J

D. -1000 J

Correct Answer: A

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Question 15

A voltaic cell consists of a zinc anode and a copper cathode. If the s\tandard reduction potential of zinc is -0.76 V and the s\tandard reduction potential of copper is +0.34 V, what is the cell potential?

Correct A. -1.1 V

B. -0.9 V

C. -0.7 V

D. -0.5 V

Correct Answer: A

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Question 16

The solubility of a gas in a liquid is influenced by the following factors: temperature, pressure, and the nature of the gas and liquid. Which of the following statements is NOT true about the solubility of a gas in a liquid?

A. The solubility of a gas in a liquid increases with increa\sing temperature.

B. The solubility of a gas in a liquid decreases with increa\sing pressure.

Correct C. The solubility of a gas in a liquid is indep\endent of the nature of the gas and liquid.

D. The solubility of a gas in a liquid increases with increa\sing pressure.

Correct Answer: C

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Question 17

A 0.1 M solution of a weak acid HA is 5% ionized at 25°C. Calculate the pH of the solution.

A. 2.3

Correct B. 2.5

C. 2.7

D. 2.9

Correct Answer: B

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Question 18

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 19

A sample of a polymer has a molecular weight of 100,000 g/mol. If the polymer is composed of 80% monomer A and 20% monomer B, what is the average molecular weight of the polymer?

A. 80,000 g/mol

Correct B. 90,000 g/mol

C. 100,000 g/mol

D. 110,000 g/mol

Correct Answer: B

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Question 20

The diagram below shows a simple black and white chemistry apparatus showing 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 21

The reaction between chlorine gas and potassium iodide is a classic example of a redox reaction. Write the balanced chemical equation for this reaction, including the states of matter for each reac\tant and product.

A. Cl2(g) + 2KI(s) → 2KCl(s) + I2(s)

Correct B. Cl2(g) + 2KI(s) → 2KCl(s) + I2(g)

C. Cl2(g) + 2KI(l) → 2KCl(l) + I2(g)

D. Cl2(l) + 2KI(s) → 2KCl(s) + I2(g)

Correct Answer: B

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Question 22

A sample of nitrogen gas at 25°C and 1 atm is allowed to expand into a larger container. If the final temperature is 50°C and the final pressure is 0.5 atm, what is the final volume of the gas?

Correct A. 0.25 m³

B. 0.5 m³

C. 1 m³

D. 2 m³

Correct Answer: A

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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 CO(g)?

Correct A. -110.5 kJ/mol

B. -110.5 kJ/mol

C. -110.5 kJ/mol

D. -110.5 kJ/mol

Correct Answer: A

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Question 24

A 2.5 M solution of HCl is mixed with a 1.5 M solution of NaOH. What is the concentration of the resulting solution?

A. 1.5 M

B. 2.5 M

Correct C. 3.5 M

D. 4.5 M

Correct Answer: C

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Question 25

A sample of oxygen gas at 25°C and 1 atm is compressed to a final pressure of 5 atm. What is the final temperature of the gas?

A. 50°C

B. 75°C

C. 100°C

Correct D. 125°C

Correct Answer: D

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