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POST UTME LASU 2021 Chemistry | Objective

Are you preparing for POST UTME LASU exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2021 Chemistry (Objective) questions designed to simulate the real exam environment.

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Question 1

Determine the number of moles of oxygen gas (O2) that will react with 2.50 moles of propane (C3H8) according to the balanced equation: 2C3H8 + 19O2 → 12CO2 + 14H2O.

A. 0.50 mol

Correct B. 1.00 mol

C. 1.50 mol

D. 2.00 mol

Correct Answer: B

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Question 2

A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the pH of the solution after the addition of 25.0 mL of NaOH.

A. 1.00

B. 2.00

C. 3.00

Correct D. 4.00

Correct Answer: D

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Question 3

The rate cons\tant (k) for the decomposition of N2O5 is 2.50 × 10^\( -3 \) s^\( -1 \) at 25°C. Calculate the half-life \( t1/2 \) of N2O5.

A. 1.00 × 10^3 s

B. 1.00 × 10^4 s

Correct C. 1.00 × 10^5 s

D. 1.00 × 10^6 s

Correct Answer: C

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Question 4

A 2.00 L sample of 0.100 M H2SO4 is titrated with 0.100 M NaOH. Calculate the number of moles of H2SO4.

A. 0.0100 mol

B. 0.0200 mol

C. 0.0300 mol

Correct D. 0.0400 mol

Correct Answer: D

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Question 5

The diagram below shows a titration setup.

A. The burette contains HCl.

Correct B. The beaker contains NaOH.

C. The burette contains NaOH.

D. The beaker contains HCl.

Correct Answer: B

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Question 6

In a redox reaction, what is the role of the oxidizing agent?

A. To donate electrons

Correct B. To accept electrons

C. To facilitate the reaction

D. To inhibit the reaction

Correct Answer: B

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Question 7

What is the major difference between primary and secondary alcohols?

A. Primary alcohols have a higher boiling point than secondary alcohols

Correct B. Secondary alcohols have a higher boiling point than primary alcohols

C. Primary alcohols are more soluble in water than secondary alcohols

D. Secondary alcohols are more soluble in water than primary alcohols

Correct Answer: B

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Question 8

A 2.5 g sample of a metal oxide is heated in a crucible. The mass of the oxide is reduced to 1.8 g. What is the percentage decrease in mass?

A. 10%

Correct B. 20%

C. 30%

D. 40%

Correct Answer: B

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Question 9

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 10

A diagram of a titration setup is shown below. 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 mix the solutions

D. To heat the solutions

Correct Answer: A

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Question 11

Determine the number of unpaired electrons in the ground state of a neutral atom of the element with atomic number 13.

A. 4

Correct B. 6

C. 8

D. 10

Correct Answer: B

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Question 12

A 0.5 M solution of NaOH is mixed with a 0.5 M solution of HCl. What is the pH of the resulting solution?

A. 1

Correct B. 7

C. 10

D. 12

Correct Answer: B

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Question 13

A sample of a polymer is analyzed and found to have a molecular weight of 50,000 g/mol. If the polymer has a degree of polymerization of 500, what is the molecular weight of the repeating unit?

A. 50

B. 100

Correct C. 500

D. 1000

Correct Answer: C

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Question 14

A colloidal solution is prepared by mixing 10 mL of a 0.1 M solution of FeCl3 with 10 mL of a 0.1 M solution of NaOH. What is the type of colloid formed?

Correct A. Sol

B. Emulsion

C. Foam

D. Gel

Correct Answer: A

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Question 15

A metal is extracted from its ore by the process of electrolysis. What is the purpose of the electrolyte in this process?

A. To conduct electricity

Correct B. To provide a medium for the reaction

C. To purify the metal

D. To increase the temperature

Correct Answer: B

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Question 16

Determine the rate cons\tant (k) for the reaction: 2NO(g) + O2(g) → 2NO2(g), given that the initial concentration of NO is 0.5 M, the initial concentration of O2 is 0.2 M, and after 10 minutes, the concentration of NO2 is 0.4 M. The rate cons\tant (k) is related to the rate cons\tant (k') by the equation: k = k' / \( 1 + k' * t \), where t is the time in minutes.

A. 0.05 min^-1

Correct B. 0.1 min^-1

C. 0.2 min^-1

D. 0.5 min^-1

Correct Answer: B

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Question 17

A 0.5 M solution of HCl is titrated with a 0.5 M solution of NaOH. If 25 mL of NaOH is required to reach the equivalence point, what is the pH of the solution at this point?

A. 1

B. 2

Correct C. 7

D. 14

Correct Answer: C

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Question 18

A sample of CO2 gas is collected over water at a temperature of 25°C and a pressure of 1 atm. If the volume of the gas is 2 L, what is the partial pressure of CO2?

A. 0.5 atm

Correct B. 0.75 atm

C. 1 atm

D. 1.5 atm

Correct Answer: B

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Question 19

A 1 M solution of NaOH is mixed with a 1 M solution of HCl. If the initial pH of the NaOH solution is 12, what is the pH of the solution after the reaction?

A. 1

B. 2

Correct C. 7

D. 14

Correct Answer: C

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Question 20

A 0.5 M solution of H2SO4 is titrated with a 0.5 M solution of NaOH. If 20 mL of NaOH is required to reach the equivalence point, what is the pH of the solution at this point?

A. 1

B. 2

Correct C. 7

D. 14

Correct Answer: C

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Question 21

Determine the pH of a 0.1 M solution of HCl at 25°C if the concentration of H+ ions is 0.05 M.

A. 1.0

Correct B. 2.0

C. 3.0

D. 4.0

Correct Answer: B

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Question 22

A 25 mL sample of 0.5 M H2SO4 is titrated with 0.5 M NaOH. Calculate the volume of NaOH required to reach the equivalence point.

A. 12.5 mL

B. 25 mL

Correct C. 37.5 mL

D. 50 mL

Correct Answer: C

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Question 23

A 1.0 L solution of 0.1 M NaOH is mixed with 1.0 L of 0.1 M HCl. What is the pH of the resulting solution?

Correct A. 7.0

B. 8.0

C. 9.0

D. 10.0

Correct Answer: A

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Question 24

A 2.0 L solution of 0.2 M H2SO4 is mixed with 2.0 L of 0.2 M NaOH. What is the pH of the resulting solution?

A. 2.0

Correct B. 3.0

C. 4.0

D. 5.0

Correct Answer: B

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Question 25

A 1.0 L solution of 0.1 M HCl is mixed with 1.0 L of 0.1 M NaOH. What is the pH of the resulting solution?

A. 1.0

Correct B. 2.0

C. 3.0

D. 4.0

Correct Answer: B

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