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POST UTME UNN 2025 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 2025 Chemistry (Objective) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1

Determine the pH of a 0.1 M solution of HCl.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 2

A diagram of a titration setup is shown below. If 25.0 mL of 0.1 M NaOH is required to reach the equivalence point, what is the concentration of the HCl 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 3

A sample of CO2 gas is collected over water at a temperature of 25°C and a pressure of 1 atm. If the partial pressure of CO2 is 0.5 atm, what is the mole \fraction of CO2 in the gas mixture?

Correct A. 0.25

B. 0.5

C. 0.75

D. 0.9

Correct Answer: A

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Question 4

A diagram of a simple distillation apparatus is shown below. If the boiling point of the solvent is 100°C and the boiling point of the impurity is 120°C, what is the minimum temperature required to separate the impurity from the solvent?

A. 110°C

B. 115°C

Correct C. 120°C

D. 125°C

Correct Answer: C

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Question 5

A sample of polystyrene is analyzed by gel permeation chromatography (GPC). The chromatogram shows a \single peak with a retention time of 10 minutes. If the calibration curve is linear, what is the molecular weight of the polystyrene sample?

A. 100,000 g/mol

B. 200,000 g/mol

Correct C. 500,000 g/mol

D. 1,000,000 g/mol

Correct Answer: C

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Question 6

The reaction between chlorine gas and potassium iodide is a classic example of a redox reaction. What is the oxidation state of iodine in KI?

A. 0

B. -1

Correct C. +1

D. +2

Correct Answer: C

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Question 7

A 2.50 g sample of a metal carbonate is heated to produce a metal oxide and carbon dioxide gas. If the mass of the metal oxide produced is 1.75 g, what is the molar mass of the metal carbonate?

A. 100 g/mol

B. 150 g/mol

Correct C. 200 g/mol

D. 250 g/mol

Correct Answer: C

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Question 8

The s\tandard enthalpy of formation of CO2 is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of CO?

Correct A. -110.5 kJ/mol

B. -130.5 kJ/mol

C. -150.5 kJ/mol

D. -170.5 kJ/mol

Correct Answer: A

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Question 9

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

Correct A. 0.76 atm

B. 0.86 atm

C. 0.96 atm

D. 1.06 atm

Correct Answer: A

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Question 10

A 2.00 g sample of a non-metallic element is heated in a crucible until it is completely vaporized. If the mass of the crucible and its contents after heating is 2.50 g, what is the molar mass of the element?

A. 50 g/mol

B. 60 g/mol

Correct C. 70 g/mol

D. 80 g/mol

Correct Answer: C

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Question 11

Determine the molar mass of a gas that occupies 2.5 L at 27°C and 1.2 atm. Use the ideal gas law to calculate the number of moles.

A. \( 2.5 , \text{L} \times 1.2 , \text{atm} \times 0.0821 , \text{L atm/mol K} \times 300 , \text{K} \)

Correct B. \( 2.5 , \text{L} \times 1.2 , \text{atm} \times 0.0821 , \text{L atm/mol K} \times 300 , \text{K} \times 6.022 \times 10^{23} \)

C. \( 2.5 , \text{L} \times 1.2 , \text{atm} \times 0.0821 , \text{L atm/mol K} \times 300 , \text{K} \times 6.022 \times 10^{23} \times 4.184 , \text{J/g°C} \)

D. \( 2.5 , \text{L} \times 1.2 , \text{atm} \times 0.0821 , \text{L atm/mol K} \times 300 , \text{K} \times 6.022 \times 10^{23} \times 4.184 , \text{J/g°C} \times 10^{-3} , \text{kg/g} \)

Correct Answer: B

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Question 12

A metal alloy consists of 75% copper and 25% zinc. If 2.5 kg of the alloy is melted and cast into a cylindrical shape, what is the volume of the cylinder?

A. \( 2.5 , \text{kg} \times 0.75 \times 8.9 , \text{g/cm}^3 \)

B. \( 2.5 , \text{kg} \times 0.75 \times 8.9 , \text{g/cm}^3 \times 1000 , \text{cm}^3/\text{L} \)

Correct C. \( 2.5 , \text{kg} \times 0.75 \times 8.9 , \text{g/cm}^3 \times 1000 , \text{cm}^3/\text{L} \times pi , \text{r}^2 \)

D. \( 2.5 , \text{kg} \times 0.75 \times 8.9 , \text{g/cm}^3 \times 1000 , \text{cm}^3/\text{L} \times pi , \text{r}^2 \times 2 , \text{cm} \)

Correct Answer: C

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Question 13

A polymer consists of repeating units of the following structure: CH2=CH-CH2-CH3. What is the molar mass of this polymer?

A. \( 28 , \text{g/mol} \)

B. \( 28 , \text{g/mol} \times 2 \)

Correct C. \( 28 , \text{g/mol} \times 3 \)

D. \( 28 , \text{g/mol} \times 4 \)

Correct Answer: C

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Question 14

A solution of ethanol (C2H5OH) is 20% by volume. If 2.5 L of this solution is diluted to 5.0 L, what is the new concentration?

A. \( 20% , \text{v/v} \)

B. \( 10% , \text{v/v} \)

Correct C. \( 5% , \text{v/v} \)

D. \( 2.5% , \text{v/v} \)

Correct Answer: C

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Question 15

A sample of a metal oxide has a mass of 25 g and a volume of 2.5 cm3. What is the density of the metal oxide?

A. \( 10 , \text{g/cm}^3 \)

B. \( 20 , \text{g/cm}^3 \)

Correct C. \( 30 , \text{g/cm}^3 \)

D. \( 40 , \text{g/cm}^3 \)

Correct Answer: C

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Question 16

The reaction between chlorine gas and ammonia is highly exothermic. What is the balanced chemical equation for this reaction?

Correct A. \text{Cl}_2 + \text{NH}_3 \rightarrow \text{NH}_4\text{Cl} + \text{HCl}

B. \text{Cl}_2 + \text{NH}_3 \rightarrow \text{NH}_3\text{Cl} + \text{HCl}

C. \text{Cl}_2 + \text{NH}_3 \rightarrow \text{NH}_4\text{Cl} + \text{NH}_3

D. \text{Cl}_2 + \text{NH}_3 \rightarrow \text{NH}_3\text{Cl} + \text{NH}_3

Correct Answer: A

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Question 17

A 2.5 M solution of sodium hydroxide is prepared by dissolving 12.5 g of NaOH in water to make 1 L of solution. What is the concentration of the solution in moles per liter?

Correct A. 2.5 M

B. 5 M

C. 10 M

D. 12.5 M

Correct Answer: A

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Question 18

A solution of 0.1 M HCl is titrated with 0.1 M NaOH. What is the pH of the solution after 10 mL of NaOH has been added?

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 19

A 1 L solution of 0.5 M NaCl is prepared by dissolving 25 g of NaCl in water. What is the concentration of the solution in moles per liter?

Correct A. 0.5 M

B. 1 M

C. 2 M

D. 5 M

Correct Answer: A

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Question 20

A 2 L solution of 0.2 M H2SO4 is prepared by dissolving 40 g of H2SO4 in water. What is the concentration of the solution in moles per liter?

Correct A. 0.2 M

B. 0.4 M

C. 0.6 M

D. 0.8 M

Correct Answer: A

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Question 21

A solution of 0.1 M HCl is titrated with 0.1 M NaOH. What is the pH of the solution after 20 mL of NaOH has been added?

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 22

A 1 L solution of 0.5 M NaCl is prepared by dissolving 25 g of NaCl in water. What is the concentration of the solution in moles per liter?

Correct A. 0.5 M

B. 1 M

C. 2 M

D. 5 M

Correct Answer: A

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Question 23

A 2 L solution of 0.2 M H2SO4 is prepared by dissolving 40 g of H2SO4 in water. What is the concentration of the solution in moles per liter?

Correct A. 0.2 M

B. 0.4 M

C. 0.6 M

D. 0.8 M

Correct Answer: A

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Question 24

A solution of 0.1 M HCl is titrated with 0.1 M NaOH. What is the pH of the solution after 30 mL of NaOH has been added?

A. 1

B. 2

C. 3

D. 4

Correct Answer: VIEW ANSWER

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Question 25

Determine the pH of a 0.1 M solution of HCl at 25°C, given that the dissociation cons\tant of HCl is 10^\( -7 \) and the temperature dep\endence of the dissociation cons\tant is described by the equation \( \log_{10} K = -\frac{1000}{2.303RT} \), where R is the gas cons\tant and T is the temperature in Kelvin.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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