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POST UTME NILE UNIVERSITY 2021 Chemistry | Objective

Are you preparing for POST UTME NILE UNIVERSITY 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.

Practice these randomly selected questions to test your readiness.

Question 1

Determine the s\tandard electrode potential of the cell represented by the following reaction: MnO4- + 8H+ + 5e- → Mn2+ + 4H2O. Given that the s\tandard electrode potential of the MnO4-/Mn2+ couple is +1.23 V.

A. +1.23 V

Correct B. +1.46 V

C. +1.69 V

D. +1.92 V

Correct Answer: B

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Question 2

A 0.5 M solution of H2SO4 is prepared by dissolving 9.0 g of H2SO4 in 1.0 L of water. What is the concentration of H+ ions in the solution?

A. 0.1 M

B. 0.2 M

Correct C. 0.5 M

D. 1.0 M

Correct Answer: C

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Question 3

A sample of nitrogen gas is collected over water at a temperature of 25°C and a pressure of 1.0 atm. If the vapor pressure of water at 25°C is 0.0313 atm, what is the partial pressure of nitrogen 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 4

A solution contains 0.1 M NaCl. What is the concentration of Cl- ions in the solution?

A. 0.05 M

Correct B. 0.1 M

C. 0.15 M

D. 0.2 M

Correct Answer: B

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Question 5

A 2.0 M solution of HCl is prepared by dissolving 36.5 g of HCl in 1.0 L of water. What is the concentration of H+ ions in the solution?

A. 1.0 M

B. 1.5 M

Correct C. 2.0 M

D. 2.5 M

Correct Answer: C

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Question 6

In the electrolysis of a solution of silver nitrate, the anode is made of platinum and the cathode is made of silver. The reaction at the anode is:

Correct A. 2Ag+(aq) + 2e- → Ag(s)

B. 2Ag+(aq) + 2e- → Ag2O(s)

C. 2Ag+(aq) + 2e- → Ag2O2(s)

D. 2Ag+(aq) + 2e- → Ag2O3(s)

Correct Answer: A

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Question 7

A solution of sodium chloride is electrolyzed u\sing a platinum electrode. The reaction at the cathode is:

Correct A. 2Na+(aq) + 2e- → Na(s)

B. 2Cl-(aq) + 2e- → Cl2(g)

C. 2Na+(aq) + 2e- → Na2(g)

D. 2Cl-(aq) + 2e- → Cl2(s)

Correct Answer: A

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Question 8

A colloidal solution of gold is prepared by the reduction of gold chloride u\sing a reducing agent. The reaction is:

Correct A. Au3+(aq) + 3e- → Au(s)

B. Au3+(aq) + 3e- → Au2O3(s)

C. Au3+(aq) + 3e- → Au2O(s)

D. Au3+(aq) + 3e- → Au2O2(s)

Correct Answer: A

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Question 9

A polymer is prepared by the condensation reaction of two monomers. The reaction is:

Correct A. A + B → AB + C

B. A + B → AB + D

C. A + B → AC + D

D. A + B → AD + C

Correct Answer: A

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Question 10

A non-metal is prepared by the reaction of a metal with a non-metal. The reaction is:

Correct A. 2Na + Cl2 → 2NaCl

B. 2Na + S → Na2S

C. 2Na + O2 → Na2O

D. 2Na + N2 → Na2N2

Correct Answer: A

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Question 11

The reaction of nitrogen with oxygen to form nitrogen dioxide is an example of a redox reaction. Write the balanced chemical equation for this reaction, including the s\tandard enthalpy change (ΔH°) and the s\tandard entropy change (ΔS°).

Correct A. 2NO + O2 → 2NO2, ΔH° = -114.2 kJ/mol, ΔS° = -146.4 J/mol K

B. 2NO2 + O2 → 2NO, ΔH° = 114.2 kJ/mol, ΔS° = 146.4 J/mol K

C. 2NO + O2 → 2NO2, ΔH° = 114.2 kJ/mol, ΔS° = 146.4 J/mol K

D. 2NO2 + O2 → 2NO, ΔH° = -114.2 kJ/mol, ΔS° = -146.4 J/mol K

Correct Answer: A

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Question 12

A 2.50 M solution of sulfuric acid (H2SO4) is mixed with a 1.25 M solution of sodium hydroxide (NaOH). Calculate the number of moles of sulfuric acid that react with sodium hydroxide to form water and sodium sulfate.

Correct A. 0.5 mol

B. 1.0 mol

C. 1.5 mol

D. 2.0 mol

Correct Answer: A

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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.

Correct A. -110.5 kJ/mol

B. -120.5 kJ/mol

C. -130.5 kJ/mol

D. -140.5 kJ/mol

Correct Answer: A

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Question 14

A sample of hydrogen gas (H2) is collected over water at a temperature of 25°C and a pressure of 1.00 atm. Calculate the partial pressure of hydrogen gas in the sample.

A. 0.50 atm

Correct B. 0.75 atm

C. 1.00 atm

D. 1.25 atm

Correct Answer: B

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Question 15

A 1.00 M solution of sodium chloride (NaCl) is mixed with a 1.00 M solution of hydrochloric acid (HCl). Calculate the concentration of the resulting solution.

A. 0.25 M

Correct B. 0.50 M

C. 0.75 M

D. 1.00 M

Correct Answer: B

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Question 16

Determine the molar mass of a polymer with the following composition: 60% polyethylene (C2H4) and 40% polypropylene (C3H6).

A. 60 g/mol

Correct B. 120 g/mol

C. 180 g/mol

D. 240 g/mol

Correct Answer: B

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Question 17

A 2.0 L container is filled with 1.5 mol of an ideal gas at 27°C. Calculate the pressure of the gas u\sing the ideal gas law.

A. 2.5 atm

Correct B. 3.0 atm

C. 3.5 atm

D. 4.0 atm

Correct Answer: B

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Question 18

A redox reaction involves the oxidation of Cu(s) to Cu2+(aq) and the reduction of MnO4-(aq) to Mn2+(aq). Write the balanced half-reactions and the overall balanced equation.

Correct A. Cu(s) → Cu2+(aq) + 2e-; MnO4-(aq) + 8H+(aq) + 5e- → Mn2+(aq) + 4H2O(l)

B. Cu(s) → Cu2+(aq) + 2e-; MnO4-(aq) + 2H2O(l) + 3e- → Mn2+(aq) + 4OH-(aq)

C. Cu(s) → Cu2+(aq) + 2e-; MnO4-(aq) + 4H+(aq) + 3e- → Mn2+(aq) + 2H2O(l)

D. Cu(s) → Cu2+(aq) + 2e-; MnO4-(aq) + 6H+(aq) + 4e- → Mn2+(aq) + 3H2O(l)

Correct Answer: A

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Question 19

A 25.0 g sample of a subs\tance is found to have a mass of 10.0 g after being burned in air. If the subs\tance is composed of 85.0% carbon and 15.0% hydrogen, calculate the energy released per gram of the subs\tance.

A. -3.5 kJ/g

Correct B. -4.5 kJ/g

C. -5.5 kJ/g

D. -6.5 kJ/g

Correct Answer: B

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Question 20

A diagram of a simple harmonic oscillator is shown below. If the oscillator has a mass of 2.0 kg and a spring cons\tant of 100 N/m, calculate the frequency of oscillation.

A. 1.0 Hz

Correct B. 2.0 Hz

C. 3.0 Hz

D. 4.0 Hz

Correct Answer: B

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Question 21

Determine the number of moles of oxygen gas produced when 2.5 moles of calcium carbonate are decomposed according to the equation: CaCO3(s) → CaO(s) + CO2(g) + 1/2O2(g).

Correct A. 1.25

B. 2.5

C. 3.75

D. 5

Correct Answer: A

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Question 22

A 0.5 M solution of sodium hydroxide is mixed with a 0.5 M solution of hydrochloric acid. What is the pH of the resulting solution?

Correct A. 7

B. 8

C. 9

D. 10

Correct Answer: A

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Question 23

A diagram of a titration setup is shown below. If the burette contains 25 mL of 0.1 M sodium hydroxide and the titration requires 15 mL of the base to reach the \endpoint, what is the concentration of the acid?

A. 0.05 M

B. 0.1 M

Correct C. 0.2 M

D. 0.5 M

Correct Answer: C

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Question 24

A sample of a gas at 25°C and 1 atm is found to have a volume of 2.5 L. What is the number of moles of the gas?

A. 0.1

Correct B. 0.2

C. 0.3

D. 0.4

Correct Answer: B

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Question 25

A diagram of a gas law setup is shown below. If the initial pressure is 1 atm and the final pressure is 2 atm, what is the final volume?

A. 2.5 L

Correct B. 5 L

C. 10 L

D. 20 L

Correct Answer: B

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