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POST UTME NILE UNIVERSITY 2025 Chemistry | Objective

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Question 1

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 2

A 0.500 M solution of HCl(aq) is titrated with 0.500 M NaOH(aq). If 25.0 mL of NaOH(aq) is required to reach the equivalence point, what is the pH of the resulting solution?

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 3

The diagram below shows a titration setup.

Correct A. The burette contains HCl(aq).

B. The burette contains NaOH(aq).

C. The beaker contains HCl(aq).

D. The beaker contains NaOH(aq).

Correct Answer: A

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Question 4

The s\tandard enthalpy of formation of NH3(g) is -45.9 kJ/mol. Calculate the s\tandard enthalpy of formation of NH4Cl(s) u\sing the following reaction: NH3(g) + HCl(g) → NH4Cl(s).

A. -206.8 kJ/mol

B. -206.8 kJ/mol

C. -206.8 kJ/mol

Correct D. -206.8 kJ/mol

Correct Answer: D

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Question 5

A 0.100 M solution of H2SO4(aq) is titrated with 0.100 M NaOH(aq). If 50.0 mL of NaOH(aq) is required to reach the equivalence point, what is the pH of the resulting solution?

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 6

The reaction of cyclohexane with bromine in the presence of light produces a mixture of 1,2-dibromocyclohexane and 1,4-dibromocyclohexane. What is the major product of this reaction?

A. 1,2-dibromocyclohexane

Correct B. 1,4-dibromocyclohexane

C. cis-1,2-dibromocyclohexane

D. trans-1,2-dibromocyclohexane

Correct Answer: B

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Question 7

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of H2O(l) if the s\tandard enthalpy of formation of CO(g) is -110.5 kJ/mol and that of H2(g) is 0 kJ/mol?

Correct A. -285.8 kJ/mol

B. -241.8 kJ/mol

C. -393.5 kJ/mol

D. -110.5 kJ/mol

Correct Answer: A

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Question 8

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

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 separate the titrant and analyte

Correct Answer: A

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Question 9

The s\tandard enthalpy of formation of NH3(g) is -45.9 kJ/mol. What is the s\tandard enthalpy of formation of N2(g) if the s\tandard enthalpy of formation of H2(g) is 0 kJ/mol?

Correct A. 0 kJ/mol

B. -45.9 kJ/mol

C. -90.9 kJ/mol

D. -180.9 kJ/mol

Correct Answer: A

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Question 10

The diagram below shows a simple black and white chemistry apparatus showing a titration setup. What is the purpose of the burette in this setup?

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 separate the titrant and analyte

Correct Answer: A

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Question 11

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

Correct A. 12.5 mL

B. 25 mL

C. 37.5 mL

D. 50 mL

Correct Answer: A

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Question 12

A sample of air contains 20% O2, 70% N2, and 10% CO2 by volume. What is the partial pressure of CO2 in a sample of air at 1 atm total pressure?

Correct A. 0.1 atm

B. 0.2 atm

C. 0.3 atm

D. 0.4 atm

Correct Answer: A

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Question 13

A 2.0 g sample of an unknown hydrocarbon is burned in a bomb calorimeter, relea\sing 12.5 kJ of heat. What is the empirical formula of the hydrocarbon?

Correct A. C2H4

B. C3H6

C. C4H8

D. C5H10

Correct Answer: A

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Question 14

A 0.1 M solution of H2SO4 is titrated with 0.1 M NaOH. If 20 mL of H2SO4 is required to reach the equivalence point, what is the pH of the solution at the equivalence point?

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 15

A sample of a salt is dissolved in water to give a solution with a pH of 7. What is the nature of the salt?

A. Acidic

B. Basic

Correct C. Neutral

D. Amphoteric

Correct Answer: C

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Question 16

The rate cons\tant of a first-order reaction is 0.05 min^-1. If the initial concentration of the reac\tant is 0.1 M, what is the concentration of the reac\tant after 10 minutes?

Correct A. 0.01 M

B. 0.05 M

C. 0.1 M

D. 0.2 M

Correct Answer: A

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Question 17

A polymer has a molecular weight of 50000 g/mol. If the molar mass of the monomer is 100 g/mol, what is the degree of polymerization?

A. 50

B. 100

Correct C. 500

D. 1000

Correct Answer: C

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Question 18

A solution of HCl is 0.1 M. If 10 mL of this solution is titrated with 0.1 M NaOH, what is the pH of the solution after the titration?

A. 1

B. 2

Correct C. 3

D. 4

Correct Answer: C

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Question 19

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?

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 20

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

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 21

The polymerization of styrene in the presence of benzoyl peroxide as an initiator yields a polymer with a degree of polymerization (DP) of 1000. If the number-average molecular weight (Mn) of the polymer is 50000 g/mol, what is the weight-average molecular weight (Mw)?

Correct A. 250000 g/mol

B. 50000 g/mol

C. 100000 g/mol

D. 200000 g/mol

Correct Answer: A

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Question 22

A sample of sulfur (S) is heated in a stream of oxygen gas (O2) to produce sulfur dioxide (SO2). If 2.5 g of sulfur is heated for 10 minutes, and the reaction is 90% complete, what is the total mass of sulfur dioxide produced?

A. 10.5 g

Correct B. 12.5 g

C. 15.5 g

D. 18.5 g

Correct Answer: B

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Question 23

The atomic radius of a certain metal is 100 pm. If the metal is in the +2 oxidation state, what is the ionic radius of the metal ion?

Correct A. 90 pm

B. 95 pm

C. 100 pm

D. 105 pm

Correct Answer: A

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Question 24

A solution of sodium chloride (NaCl) is prepared by dissolving 10 g of NaCl in 100 mL of water. What is the molarity of the solution?

Correct A. 0.1 M

B. 0.5 M

C. 1.0 M

D. 2.0 M

Correct Answer: A

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Question 25

A sample of hydrogen gas (H2) is collected over water at a temperature of 25°C and a pressure of 1 atm. What is the partial pressure of hydrogen gas in the sample?

A. 0.5 atm

Correct B. 0.75 atm

C. 1.0 atm

D. 1.25 atm

Correct Answer: B

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