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POST UTME UNN 2024 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 2024 Chemistry (Objective) questions designed to simulate the real exam environment.

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Question 1

A sample of an ideal gas is heated from 300 K to 400 K at cons\tant volume. What is the ratio of the final pressure to the initial pressure?

Correct A. 1.33

B. 2.00

C. 1.00

D. 0.75

Correct Answer: A

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Question 2

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

A. To measure the volume of the acid

Correct B. To measure the volume of the base

C. To measure the pH of the solution

D. To mix the acid and base

Correct Answer: B

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Question 3

A polymer has a molecular weight of 100,000 g/mol. If 2.5 g of the polymer is dissolved in 50 mL of solvent, what is the concentration of the solution in g/L?

A. 0.05 g/L

B. 0.5 g/L

Correct C. 5.0 g/L

D. 50 g/L

Correct Answer: C

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Question 4

A solution of NaOH is titrated with a solution of HCl. The pH of the solution at the equivalence point is 7. What is the concentration of the NaOH 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 5

A sample of a gas is collected over water at a temperature of 25°C and a pressure of 1 atm. The vapor pressure of water at this temperature is 0.0313 atm. What is the partial pressure of the gas?

Correct A. 0.9687 atm

B. 0.9697 atm

C. 0.9707 atm

D. 0.9717 atm

Correct Answer: A

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Question 6

A mixture of 0.5 mol of CO2 and 0.3 mol of H2O is placed in a 1 L flask at 25°C. Assuming ideal gas behavior, calculate the partial pressure of CO2 in the mixture.

A. 0.15 atm

Correct B. 0.25 atm

C. 0.35 atm

D. 0.45 atm

Correct Answer: B

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Question 7

A polymer has a molecular weight of 100,000 g/mol and a degree of polymerization of 500. Calculate the molar mass of the monomer.

A. 200 g/mol

Correct B. 250 g/mol

C. 300 g/mol

D. 350 g/mol

Correct Answer: B

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Question 8

A metal has a density of 8.5 g/cm3 and a molar mass of 65 g/mol. Calculate the number of moles of the metal in a 2.5 g sample.

Correct A. 0.038 mol

B. 0.048 mol

C. 0.058 mol

D. 0.068 mol

Correct Answer: A

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Question 9

A solution of 0.1 M HCl is mixed with a solution of 0.2 M 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 sample of air contains 20% O2, 70% N2, and 10% CO2 by volume. Calculate the partial pressure of CO2 in the sample at 1 atm.

A. 0.1 atm

Correct B. 0.2 atm

C. 0.3 atm

D. 0.4 atm

Correct Answer: B

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Question 11

Determine the number of unpaired electrons in the ground state of a copper atom, given that the atomic number of copper is 29 and the electron configuration is [Ar] 3d10 4s1.

Correct A. 1

B. 2

C. 3

D. 4

Correct Answer: A

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Question 12

A 0.5 M solution of sodium chloride (NaCl) is prepared by dissolving 25 g of NaCl in 1000 mL of water. Calculate the molarity of the solution if 10 mL of the solution is diluted to 100 mL with water.

A. 0.25 M

Correct B. 0.5 M

C. 1.0 M

D. 2.0 M

Correct Answer: B

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Question 13

The s\tandard enthalpy of formation of carbon dioxide (CO2) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of carbon monoxide (CO) if the s\tandard enthalpy of formation of carbon (C) is -717.1 kJ/mol and the s\tandard enthalpy of formation of oxygen (O2) is 0 kJ/mol.

A. -110.5 kJ/mol

B. -110.5 kJ/mol

C. -110.5 kJ/mol

Correct D. -110.5 kJ/mol

Correct Answer: D

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Question 14

A metal rod of length 50 cm and cross-sectional area 2 cm^2 is subjected to a force of 100 N. Calculate the stress and strain on the rod if the Young's modulus of the metal is 2.0 x 10^11 Pa.

A. 2.0 x 10^8 Pa, 0.01

B. 2.0 x 10^8 Pa, 0.01

C. 2.0 x 10^8 Pa, 0.01

Correct D. 2.0 x 10^8 Pa, 0.01

Correct Answer: D

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Question 15

A 2.0 M solution of sodium hydroxide (NaOH) is prepared by dissolving 40 g of NaOH in 1000 mL of water. Calculate the pH of the solution if 10 mL of the solution is diluted to 100 mL with water.

A. 13

B. 13

C. 13

Correct D. 13

Correct Answer: D

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Question 16

Determine the number of moles of $\text{O}_2$ required to react with 2.5 moles of $\text{C}_2\text{H}_4$ according to the equation: $\text{C}_2\text{H}_4 + 3\text{O}_2 \rightarrow 2\text{CO}_2 + 2\text{H}_2\text{O}$

A. 1.25 moles

B. 2.5 moles

Correct C. 3.75 moles

D. 5 moles

Correct Answer: C

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Question 17

A sample of $\text{CaCO}_3$ weighing 25.0 g is heated to produce $\text{CaO}$ and $\text{CO}_2$. If the mass of $\text{CaO}$ produced is 15.0 g, what is the mass of $\text{CO}_2$ produced?

A. 5.0 g

Correct B. 10.0 g

C. 15.0 g

D. 20.0 g

Correct Answer: B

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Question 18

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

Correct A. 12.5 mg

B. 25.0 mg

C. 50.0 mg

D. 100 mg

Correct Answer: A

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Question 19

A solution containing 2.0 M $\text{HCl}$ is mixed with a solution containing 1.0 M $\text{NaOH}$. If 50.0 mL of the $\text{HCl}$ solution is added to 50.0 mL of the $\text{NaOH}$ solution, what is the concentration of the resulting solution?

A. 1.0 M

Correct B. 1.5 M

C. 2.0 M

D. 2.5 M

Correct Answer: B

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Question 20

A 2.0 L flask contains 0.50 M $\text{CO}_2$ at 25°C. If 1.0 L of $\text{N}_2$ is added to the flask, what is the new concentration of $\text{CO}_2$?

A. 0.25 M

Correct B. 0.50 M

C. 0.75 M

D. 1.0 M

Correct Answer: B

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Question 21

Determine the number of moles of glu\cose (C6H12O6) that can be produced from 2.5 mol of ethene (C2H4) in the following reaction: C2H4 + 3O2 → C2H4O2 + 2CO2. Assume that the reaction proceeds to completion.

A. 1.5 mol

Correct B. 2.0 mol

C. 2.5 mol

D. 3.0 mol

Correct Answer: B

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Question 22

A 25.0 mL sample of 0.100 M HCl is titrated with 0.0500 M NaOH. Calculate the pH of the solution after 15.0 mL of NaOH has been added.

A. 2.00

B. 2.50

Correct C. 3.00

D. 3.50

Correct Answer: C

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Question 23

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of CH4(g) from the following reaction: C(s) + 2H2(g) → CH4(g).

A. -74.8 kJ/mol

B. -74.9 kJ/mol

Correct C. -75.0 kJ/mol

D. -75.1 kJ/mol

Correct Answer: C

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Question 24

A solution of 0.100 M NaOH is prepared by dissolving 3.00 g of NaOH in 100.0 mL of water. Calculate the pH of the solution.

A. 12.0

B. 12.1

Correct C. 12.2

D. 12.3

Correct Answer: C

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Question 25

A 2.00 L sample of 0.100 M HCl is titrated with 0.0500 M NaOH. Calculate the number of moles of NaOH required to reach the equivalence point.

A. 0.0100 mol

B. 0.0150 mol

Correct C. 0.0200 mol

D. 0.0250 mol

Correct Answer: C

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