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POST UTME OAU 2021 Chemistry | Objective

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Question 1

Determine the number of moles of electrons transferred during the electrolysis of a solution of copper(II) sulfate u\sing a current of 2.5 A for 3.2 hours. The s\tandard electrode potential for copper is +0.34 V.

A. 0.5 mol

Correct B. 1.0 mol

C. 1.5 mol

D. 2.0 mol

Correct Answer: B

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Question 2

A sample of nitrogen gas occupies a volume of 2.5 L at a pressure of 1.5 atm and a temperature of 298 K. What is the number of moles of nitrogen gas present?

A. 0.1 mol

Correct B. 0.2 mol

C. 0.3 mol

D. 0.4 mol

Correct Answer: B

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Question 3

The half-reaction for the reduction of chromium(III) ion to chromium metal is: Cr^\( 3+ \) + e^\( - \) → Cr^\( 2+ \). What is the s\tandard electrode potential for this half-reaction?

Correct A. +0.34 V

B. +0.56 V

C. +0.78 V

D. +1.00 V

Correct Answer: A

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Question 4

A solution of sodium chloride is electrolyzed u\sing a current of 5.0 A for 2.5 hours. What is the mass of chlorine gas produced at the anode?

A. 0.5 g

Correct B. 1.0 g

C. 1.5 g

D. 2.0 g

Correct Answer: B

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Question 5

A sample of hydrogen gas occupies a volume of 1.8 L at a pressure of 2.0 atm and a temperature of 273 K. What is the number of moles of hydrogen gas present?

A. 0.1 mol

Correct B. 0.2 mol

C. 0.3 mol

D. 0.4 mol

Correct Answer: B

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Question 6

A solution of potassium dichromate (K2Cr2O7) is titrated with a solution of iron(II) sulfate (FeSO4). The reaction is as follows: K2Cr2O7 + 6FeSO4 + 7H2O → K2SO4 + 2Cr(OH)3 + 6Fe(OH)3. If 25.0 mL of 0.100 M K2Cr2O7 is titrated with 0.0500 M FeSO4, what is the number of moles of FeSO4 required to react with the K2Cr2O7?

A. 0.00125 mol

Correct B. 0.00250 mol

C. 0.00500 mol

D. 0.0125 mol

Correct Answer: B

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Question 7

A sample of a gas at 25°C and 1 atm is collected over water at 25°C. The vapor pressure of water at 25°C is 23.8 mmHg. What is the partial pressure of the gas?

A. 1.00 atm

Correct B. 1.23 atm

C. 1.38 atm

D. 1.78 atm

Correct Answer: B

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Question 8

A solution of 0.100 M HCl is titrated with 0.100 M NaOH. What is the pH of the solution after 25.0 mL of NaOH has been added?

A. 1.00

B. 2.00

Correct C. 3.00

D. 4.00

Correct Answer: C

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Question 9

A 2.00 L flask contains 0.100 mol of CO2 at 25°C. What is the pressure of the gas?

A. 0.100 atm

B. 0.500 atm

Correct C. 1.00 atm

D. 2.00 atm

Correct Answer: C

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Question 10

A solution of 0.100 M HCl is titrated with 0.100 M NaOH. What is the number of moles of NaOH required to react with 25.0 mL of HCl?

A. 0.00125 mol

Correct B. 0.00250 mol

C. 0.00500 mol

D. 0.0125 mol

Correct Answer: B

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Question 11

Determine the pH of a 0.1 M solution of HCl.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 12

A 25 mL sample of 0.5 M H2SO4 is titrated with 1 M NaOH. Calculate the number of moles of NaOH required.

A. 0.025

Correct B. 0.05

C. 0.075

D. 0.1

Correct Answer: B

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Question 13

A solution contains 0.1 M HCl and 0.1 M NaOH. Calculate the pH of the solution.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 14

A 10 mL sample of 0.5 M H2SO4 is titrated with 1 M NaOH. Calculate the number of moles of NaOH required.

A. 0.05

Correct B. 0.1

C. 0.15

D. 0.2

Correct Answer: B

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Question 15

A solution contains 0.1 M HCl and 0.1 M NaOH. Calculate the pH of the solution.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 16

Determine the oxidation state of nitrogen in the compound NO2.

A. +1

B. +2

Correct C. +3

D. +4

Correct Answer: C

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Question 17

A 2.5 L flask contains 0.5 mol of an ideal gas at 27°C. Calculate the pressure of the gas.

A. 1.1 atm

Correct B. 1.2 atm

C. 1.3 atm

D. 1.4 atm

Correct Answer: B

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Question 18

A solution contains 0.1 M HCl and 0.1 M NaOH. Calculate the pH of the solution after 10 minutes.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 19

A 50 mL sample of a solution contains 0.5 g of NaCl. Calculate the molarity of the solution.

A. 0.1 M

Correct B. 0.2 M

C. 0.3 M

D. 0.4 M

Correct Answer: B

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Question 20

A 2.0 L flask contains 0.5 mol of an ideal gas at 27°C. Calculate the volume of the gas at 37°C.

A. 2.5 L

Correct B. 2.6 L

C. 2.7 L

D. 2.8 L

Correct Answer: B

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Question 21

Determine the number of moles of oxygen gas (O2) produced at STP when 2.5 moles of potassium chlorate (KClO3) decompose according to the equation: 2KClO3(s) → 2KCl(s) + 3O2(g).

A. 1.5

B. 2.5

Correct C. 3.75

D. 4.5

Correct Answer: C

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Question 22

A 25 mL sample of 0.1 M HCl is titrated with 0.1 M NaOH. Calculate the pH of the solution after the addition of 20 mL of NaOH.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 23

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

Correct A. Burette

B. Conical Flask

C. Beaker

D. Test Tube

Correct Answer: A

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Question 24

Calculate the molar mass of a compound that contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass.

A. 60.0 g/mol

B. 80.0 g/mol

Correct C. 120.0 g/mol

D. 180.0 g/mol

Correct Answer: C

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Question 25

A solution contains 0.5 M H2SO4. Calculate the pH of the solution.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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