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POST UTME REDEEMERS UNIVERSITY 2020 Chemistry | Objective

Are you preparing for POST UTME REDEEMERS UNIVERSITY exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2020 Chemistry (Objective) questions designed to simulate the real exam environment.

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Question 1

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 2

A 25.0 mL sample of 0.500 M NaOH is titrated with 0.100 M HCl. Calculate the number of moles of HCl required to reach the equivalence point.

A. 0.0125

Correct B. 0.0250

C. 0.0375

D. 0.0500

Correct Answer: B

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Question 3

A polymer has a molecular weight of 50,000 g/mol and a degree of polymerization of 500. Calculate the molar mass of the repeating unit.

A. 100

B. 200

Correct C. 500

D. 1000

Correct Answer: C

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Question 4

A 2.00 g sample of a metal oxide is dissolved in 50.0 mL of 0.100 M HCl. Calculate the number of moles of metal ions present in the solution.

A. 0.00250

Correct B. 0.00500

C. 0.00750

D. 0.0100

Correct Answer: B

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Question 5

A 1.00 L sample of a gas at 25°C and 1.00 atm is compressed to 2.00 atm. Calculate the new volume of the gas.

A. 0.500 L

B. 1.00 L

Correct C. 2.00 L

D. 4.00 L

Correct Answer: C

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Question 6

A 2.5 g sample of a metal oxide is heated in a crucible until it loses 0.75 g of oxygen. If the metal has an atomic mass of 55.85 g/mol, calculate the mass of the metal in the sample.

Correct A. 1.25 g

B. 1.5 g

C. 1.75 g

D. 2.0 g

Correct Answer: A

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Question 7

The pH of a solution is 4.5. What is the concentration of hydrogen ions in the solution?

Correct A. 1.0 x 10^-5 M

B. 1.0 x 10^-4 M

C. 1.0 x 10^-3 M

D. 1.0 x 10^-2 M

Correct Answer: A

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Question 8

A 25 mL sample of a solution containing 0.1 M HCl is titrated with 0.1 M NaOH. What is the pH of the solution after the addition of 20 mL of NaOH?

A. 2.0

Correct B. 3.0

C. 4.0

D. 5.0

Correct Answer: B

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Question 9

A metal (X) reacts with chlorine gas to form a white solid. The reaction is as follows: 2X + Cl2 → 2XCl. If 2.5 g of X reacts with 1.5 g of Cl2, what is the mass of XCl formed?

A. 3.5 g

Correct B. 4.0 g

C. 4.5 g

D. 5.0 g

Correct Answer: B

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Question 10

A solution containing 0.05 M H2SO4 is titrated with 0.05 M NaOH. What is the pH of the solution after the addition of 20 mL of NaOH?

A. 1.0

B. 2.0

Correct C. 3.0

D. 4.0

Correct Answer: C

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Question 11

The reaction between chlorine gas and sodium hydroxide solution is represented by the equation: Cl2 + 2NaOH → NaCl + NaClO + H2O. What is the oxidation state of chlorine in the product NaClO?

A. +1

B. +3

Correct C. +5

D. +7

Correct Answer: C

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Question 12

A sample of oxygen gas is collected over water at a temperature of 25°C and a pressure of 1 atm. If the partial pressure of water vapor is 0.031 atm, what is the partial pressure of oxygen gas?

A. 0.969 atm

Correct B. 0.971 atm

C. 0.973 atm

D. 0.975 atm

Correct Answer: B

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Question 13

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. What is the s\tandard enthalpy of combustion of 1 mole of methane gas?

Correct A. -890.3 kJ/mol

B. -892.3 kJ/mol

C. -894.3 kJ/mol

D. -896.3 kJ/mol

Correct Answer: A

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Question 14

A solution contains 0.5 M NaCl and 0.2 M CaCl2. What is the concentration of Cl- ions in the solution?

A. 0.5 M

Correct B. 0.6 M

C. 0.7 M

D. 0.8 M

Correct Answer: B

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Question 15

A 2.5 L flask contains 0.5 mol of an ideal gas at a temperature of 300 K. What is the pressure of the gas?

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 16

The rate cons\tant (k) of a first-order reaction is related to the half-life \( t_\( 1/2 \ \)) by the equation: \( k = \frac{ln 2}{t_{1/2}} \). What is the value of k if the half-life of the reaction is 120 minutes?

Correct A. 0.00578 min^\( -1 \)

B. 0.00578 min^\( -1 \)

C. 0.00578 min^\( -1 \)

D. 0.00578 min^\( -1 \)

Correct Answer: A

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Question 17

A sample of a polymer has a molecular weight of 200,000 g/mol. If the polymer has a degree of polymerization (n) of 500, what is the molecular weight of the repeating unit?

Correct A. 400 g/mol

B. 400 g/mol

C. 400 g/mol

D. 400 g/mol

Correct Answer: A

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Question 18

A solution of 0.1 M NaCl is mixed with a solution of 0.1 M NaOH. What is the pH of the resulting solution?

Correct A. 9.25

B. 9.25

C. 9.25

D. 9.25

Correct Answer: A

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Question 19

The s\tandard enthalpy of formation of CO_(2) is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of CO?

Correct A. -110.5 kJ/mol

B. -110.5 kJ/mol

C. -110.5 kJ/mol

D. -110.5 kJ/mol

Correct Answer: A

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Question 20

A sample of a non-metal has a mass of 2.5 g. If the density of the non-metal is 5.6 g/cm^3, what is the volume of the sample?

Correct A. 0.45 cm^3

B. 0.45 cm^3

C. 0.45 cm^3

D. 0.45 cm^3

Correct Answer: A

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Question 21

Determine the number of moles of CO2 produced from the reaction of 2.5 g of calcium carbonate (CaCO3) with excess hydrochloric acid (HCl). The molar mass of CaCO3 is 100.09 g/mol, and the molar mass of CO2 is 44.01 g/mol.

Correct A. 0.056 mol

B. 0.0565 mol

C. 0.057 mol

D. 0.0575 mol

Correct Answer: A

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Question 22

A diagram of a titration setup is shown below. If 25 mL of 0.1 M NaOH is required to neutralize 20 mL of HCl, what is the concentration of the HCl solution?

A. 0.05 M

B. 0.05 M

Correct C. 0.1 M

D. 0.2 M

Correct Answer: C

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Question 23

A sample of 1.5 g of an unknown hydrocarbon \( C_xH_y \) is burned in a combustion apparatus, producing 1.2 L of CO2 at STP. What is the empirical formula of the hydrocarbon?

A. C2H4

Correct B. C2H6

C. C3H6

D. C3H8

Correct Answer: B

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Question 24

A diagram of a simple distillation setup is shown below. If the boiling point of the mixture is 90°C, and the \fraction of the mixture that is water is 0.3, what is the boiling point of the mixture?

A. 80°C

B. 85°C

Correct C. 90°C

D. 95°C

Correct Answer: C

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Question 25

A sample of 2.0 g of an unknown compound \( C_xH_yO_z \) is dissolved in 100 mL of water, and the resulting solution is titrated with 0.1 M HCl. If 25 mL of HCl is required to neutralize the solution, what is the empirical formula of the compound?

A. C2H4O2

B. C2H6O2

Correct C. C3H6O3

D. C3H8O3

Correct Answer: C

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