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POST UTME UNIOSUN 2021 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 2021 Chemistry (Objective) questions designed to simulate the real exam environment.

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Question 1

Determine the type of hybridization exhibited by the central atom in the molecule CH2Cl2.

Correct A. sp3

B. sp2

C. sp

D. dsp3

Correct Answer: A

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Question 2

A 25.0 mL sample of 0.150 M HCl is mixed with a 25.0 mL sample of 0.100 M NaOH. Calculate the resulting pH.

A. 2.00

B. 2.50

C. 3.00

Correct D. 3.50

Correct Answer: D

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Question 3

The diagram below shows a titration setup. Identify the part labeled A.

Correct A. burette

B. pipette

C. Erlenmeyer flask

D. beaker

Correct Answer: A

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Question 4

A solution containing 0.250 mol of NaCl is diluted to a total volume of 1.50 L. Calculate the resulting concentration of NaCl.

Correct A. 0.167 M

B. 0.167 M

C. 0.250 M

D. 0.500 M

Correct Answer: A

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Question 5

The diagram below shows a simple black and white chemistry apparatus showing a titration setup. Identify the part labeled B.

A. burette

Correct B. Erlenmeyer flask

C. pipette

D. beaker

Correct Answer: B

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Question 6

A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. If the pH of the resulting solution is 7.00, what is the volume of NaOH added?

A. 12.5 mL

B. 25.0 mL

Correct C. 37.5 mL

D. 50.0 mL

Correct Answer: C

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Question 7

The rate cons\tant (k) for a first-order reaction is 0.0500 min^-1. If the initial concentration of the reac\tant is 0.100 M, what is the concentration after 10.0 minutes?

A. 0.0500 M

Correct B. 0.0700 M

C. 0.0900 M

D. 0.100 M

Correct Answer: B

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Question 8

A 2.00 g sample of an unknown hydrocarbon is burned in a bomb calorimeter. If the heat of combustion is 42.0 kJ/g, what is the molar mass of the hydrocarbon?

A. 50.0 g/mol

B. 60.0 g/mol

Correct C. 70.0 g/mol

D. 80.0 g/mol

Correct Answer: C

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Question 9

A 1.00 M solution of HCl is mixed with a 1.00 M solution of NaOH. If the resulting solution is 0.500 M HCl, what is the initial volume of the HCl solution?

A. 1.00 L

Correct B. 2.00 L

C. 3.00 L

D. 4.00 L

Correct Answer: B

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Question 10

A 2.00 g sample of an unknown nonmetal is burned in a bomb calorimeter. If the heat of combustion is 35.0 kJ/g, what is the molar mass of the nonmetal?

A. 40.0 g/mol

B. 50.0 g/mol

C. 60.0 g/mol

Correct D. 70.0 g/mol

Correct Answer: D

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Question 11

The rate cons\tant (k) of a first-order reaction is given by the equation: k = Ae^\( -Ea/RT \). If the activation energy (Ea) is 100 kJ/mol, the gas cons\tant (R) is 8.314 J/mol*K, and the temperature (T) is 300 K, what is the value of the rate cons\tant (k) if the pre-exponential factor (A) is 1.0 x 10^10 s^-1?

A. 1.0 x 10^5 s^-1

B. 1.0 x 10^6 s^-1

Correct C. 1.0 x 10^7 s^-1

D. 1.0 x 10^8 s^-1

Correct Answer: C

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Question 12

A 2.0 M solution of sulfuric acid (H2SO4) is mixed with a 1.0 M solution of sodium hydroxide (NaOH). If the reaction is complete, what is the concentration of the resulting solution?

A. 0.5 M

Correct B. 1.0 M

C. 1.5 M

D. 2.0 M

Correct Answer: B

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Question 13

A sample of nitrogen gas (N2) is collected over water at a temperature of 25°C and a pressure of 1 atm. If the vapor pressure of water at 25°C is 23.8 mmHg, what is the partial pressure of the nitrogen gas?

A. 760 mmHg

Correct B. 736.2 mmHg

C. 720 mmHg

D. 700 mmHg

Correct Answer: B

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Question 14

A 1.0 M solution of sodium chloride (NaCl) is mixed with a 1.0 M solution of calcium chloride (CaCl2). If the reaction is complete, what is the concentration of the resulting solution?

A. 0.5 M

B. 1.0 M

Correct C. 1.5 M

D. 2.0 M

Correct Answer: C

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Question 15

A sample of hydrogen gas (H2) is collected over water at a temperature of 25°C and a pressure of 1 atm. If the vapor pressure of water at 25°C is 23.8 mmHg, what is the partial pressure of the hydrogen gas?

A. 760 mmHg

Correct B. 736.2 mmHg

C. 720 mmHg

D. 700 mmHg

Correct Answer: B

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Question 16

Determine the pH of a 0.1 M solution of HCl at 25°C, given that the dissociation cons\tant of HCl is 10^\( -7 \).

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 17

A 2.5 g sample of a polymer is dissolved in 100 mL of a solvent. Calculate the molar mass of the polymer if the osmotic pressure of the solution is 2.5 atm at 25°C.

A. 1000 g/mol

B. 2000 g/mol

Correct C. 3000 g/mol

D. 4000 g/mol

Correct Answer: C

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Question 18

A 10 mL sample of a 0.1 M solution of NaOH is titrated with a 0.1 M solution of HCl. Calculate the pH of the solution after the titration.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 19

A 2.5 g sample of a polymer is dissolved in 100 mL of a solvent. Calculate the molar mass of the polymer if the osmotic pressure of the solution is 2.5 atm at 25°C.

A. 1000 g/mol

B. 2000 g/mol

Correct C. 3000 g/mol

D. 4000 g/mol

Correct Answer: C

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Question 20

A 10 mL sample of a 0.1 M solution of NaOH is titrated with a 0.1 M solution of HCl. Calculate the pH of the solution after the titration.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 21

The rate cons\tant (k) of a first-order reaction is related to the half-life \( t_\( 1/2 \ \)) by the equation: k = ln(2) / t_\( 1/2 \). If the half-life of a certain reaction is 10 minutes, what is the rate cons\tant (k) in min^\( -1 \)?

Correct A. 0.0693 min^\( -1 \)

B. 0.693 min^\( -1 \)

C. 6.93 min^\( -1 \)

D. 69.3 min^\( -1 \)

Correct Answer: A

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Question 22

A 2.5 M solution of NaCl is prepared by dissolving 2.5 g of NaCl in 100 mL of water. What is the molarity of the solution?

Correct A. 2.5 M

B. 5.0 M

C. 10.0 M

D. 15.0 M

Correct Answer: A

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Question 23

The s\tandard electrode potential (E°) of the Zn^2+/Zn couple is -0.76 V. What is the s\tandard electrode potential (E°) of the Cu^2+/Cu couple if the s\tandard electrode potential (E°) of the Cu^2+/Cu couple is 0.34 V?

Correct A. -0.42 V

B. -0.76 V

C. 0.34 V

D. 0.76 V

Correct Answer: A

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Question 24

A 10 mL sample of a 0.1 M solution of NaOH is titrated with a 0.1 M solution of HCl. What is the volume (in mL) of HCl 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 25

A 2.0 g sample of a polymer is dissolved in 100 mL of a solvent. What is the concentration \( in g/mL \) of the polymer solution?

A. 0.02 g/mL

Correct B. 0.04 g/mL

C. 0.06 g/mL

D. 0.08 g/mL

Correct Answer: B

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