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POST UTME OAU 2019 Chemistry | Objective

Are you preparing for POST UTME OAU exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2019 Chemistry (Objective) questions designed to simulate the real exam environment.

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Question 1

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 slow down the reaction

Correct Answer: B

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Question 2

A sample of nitrogen gas is collected over water at a temperature of 298 K and a pressure of 1 atm. What is the partial pressure of the nitrogen gas?

Correct A. 0.98 atm

B. 1.01 atm

C. 1.02 atm

D. 1.03 atm

Correct Answer: A

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Question 3

A 2.5 M solution of sodium hydroxide is prepared by dissolving 25 g of sodium hydroxide in water to make 1 L of solution. What is the concentration of sodium ions in the 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 4

A diagram of a titration setup is shown below. What is the purpose of the burette?

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 5

A 1.0 M solution of hydrochloric acid is prepared by dissolving 36.5 g of hydrochloric acid in water to make 1 L of solution. What is the concentration of hydrogen ions in the 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 6

Determine the number of moles of CO2 produced from the complete combustion of 2.5 g of propane (C3H8) according to the balanced equation: C3H8 + 5O2 → 3CO2 + 4H2O.

A. 0.25 mol

Correct B. 0.5 mol

C. 0.75 mol

D. 1.0 mol

Correct Answer: B

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Question 7

A 0.5 M solution of NaOH is prepared by dissolving 10 g of NaOH in water to make 1 L of solution. Calculate the concentration of the solution in mol/L.

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 8

A 0.5 M solution of NaOH is prepared by dissolving 10 g of NaOH in water to make 1 L of solution. Calculate the concentration of the solution in mol/L.

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 9

A 0.5 M solution of NaOH is prepared by dissolving 10 g of NaOH in water to make 1 L of solution. Calculate the concentration of the solution in mol/L.

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 10

A 0.5 M solution of NaOH is prepared by dissolving 10 g of NaOH in water to make 1 L of solution. Calculate the concentration of the solution in mol/L.

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 11

A 2.50 g sample of a non-metallic oxide of nitrogen is decomposed by heating with graphite. The volume of nitrogen gas produced at 25°C and 1 atm is 2.50 L. Calculate the molar mass of the oxide.

A. 60 g/mol

B. 80 g/mol

Correct C. 100 g/mol

D. 120 g/mol

Correct Answer: C

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Question 12

A 10% solution of sulfuric acid (H2SO4) is made by dissolving 10 g of the acid in 90 g of water. Calculate the molarity of the solution.

A. 0.1 M

Correct B. 0.5 M

C. 1.0 M

D. 2.0 M

Correct Answer: B

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Question 13

A colloidal solution of starch in water is prepared by adding 2 g of starch to 100 mL of water. The solution is then centrifuged at 3000 rpm for 10 minutes. Calculate the volume of the superna\tant liquid.

A. 50 mL

B. 75 mL

Correct C. 100 mL

D. 125 mL

Correct Answer: C

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Question 14

A polymer of ethylene glycol (C2H6O2) has a molecular weight of 180 g/mol. Calculate the number of repeating units in the polymer.

A. 5

B. 10

Correct C. 15

D. 20

Correct Answer: C

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Question 15

A metal (M) reacts with chlorine gas (Cl2) to form a white solid. The reaction is as follows: M + Cl2 → MCl2. If 2.5 g of MCl2 is produced, calculate the mass of M used.

Correct A. 1.25 g

B. 2.5 g

C. 3.75 g

D. 5.0 g

Correct Answer: A

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Question 16

Determine the pH of a 0.1 M solution of HCl after 10 mL of 0.1 M NaOH has been added to 20 mL of the HCl solution.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 17

A 25 mL sample of 0.2 M H2SO4 is titrated with 0.2 M NaOH. Calculate the volume of NaOH 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 18

The s\tandard electrode potential of the Mn2+/Mn couple is +1.18 V. Calculate the s\tandard electrode potential of the MnO42-/Mn couple.

A. +1.18 V

Correct B. +1.38 V

C. +1.58 V

D. +1.78 V

Correct Answer: B

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Question 19

A 1.0 M solution of Fe2+ is electrolyzed for 2.0 hours. Calculate the mass of Fe deposited at the cathode.

A. 0.1 g

Correct B. 0.2 g

C. 0.3 g

D. 0.4 g

Correct Answer: B

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Question 20

The rate cons\tant for a first-order reaction is 0.05 min-1. Calculate the half-life of the reaction.

A. 10 min

Correct B. 20 min

C. 30 min

D. 40 min

Correct Answer: B

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Question 21

The reaction of zinc metal with copper(II) sulfate solution is represented by the equation: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s). What is the oxidation state of copper in the reac\tant and product?

Correct A. +2 in reac\tant, +2 in product

B. +2 in reac\tant, -2 in product

C. -2 in reac\tant, +2 in product

D. -2 in reac\tant, -2 in product

Correct Answer: A

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Question 22

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of CaCO3(s) from the following reaction: Ca(s) + CO2(g) → CaCO3(s).

Correct A. -1201.0 kJ/mol

B. -1201.5 kJ/mol

C. -1202.0 kJ/mol

D. -1202.5 kJ/mol

Correct Answer: A

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Question 23

A 2.50 g sample of a non-metallic element is found to have a mass of 1.25 g after being heated in a Bunsen burner. What is the percentage increase in mass?

A. 25.0%

Correct B. 50.0%

C. 75.0%

D. 100.0%

Correct Answer: B

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Question 24

The half-life of a radioactive subs\tance is 5.00 days. If a sample initially contains 100.0 g of the subs\tance, what is the mass remaining after 20.0 days?

Correct A. 25.0 g

B. 50.0 g

C. 75.0 g

D. 100.0 g

Correct Answer: A

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Question 25

A solution containing 0.100 M NaCl is prepared by dissolving 10.0 g of NaCl in 1.00 L of water. What is the concentration of Cl- ions in the solution?

A. 0.0500 M

Correct B. 0.100 M

C. 0.150 M

D. 0.200 M

Correct Answer: B

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