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POST UTME EKSU 2025 Chemistry | Objective

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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 2.5 g sample of a metal carbonate is heated to produce a metal oxide and carbon dioxide gas. If the mass of the metal oxide produced is 1.8 g, what is the percentage yield of the reaction?

A. 50%

B. 60%

Correct C. 70%

D. 80%

Correct Answer: C

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Question 3

A solution of sodium hydroxide (NaOH) is added to a solution of hydrochloric acid (HCl) in a titration experiment. If 25 cm^3 of 0.1 M NaOH is required to neutralize 50 cm^3 of 0.2 M HCl, what is the concentration of the NaOH solution?

A. 0.05 M

Correct B. 0.1 M

C. 0.2 M

D. 0.5 M

Correct Answer: B

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Question 4

A diagram of a titration setup is shown below. If the burette contains 25 cm^3 of 0.1 M NaOH and the volume of the acid solution is 50 cm^3, what is the concentration of the acid solution?

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 5

A 2.5 g sample of a metal carbonate is heated to produce a metal oxide and carbon dioxide gas. If the mass of the metal oxide produced is 1.8 g, what is the percentage yield of the reaction?

A. 50%

B. 60%

Correct C. 70%

D. 80%

Correct Answer: C

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Question 6

Determine the molar mass of a compound containing 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. The atomic masses of carbon, hydrogen, and oxygen are 12.01 g/mol, 1.008 g/mol, and 16.00 g/mol, respectively.

A. 120.0 g/mol

Correct B. 150.0 g/mol

C. 180.0 g/mol

D. 200.0 g/mol

Correct Answer: B

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Question 7

A 2.50 L sample of a gas at 25°C and 1.00 atm is collected over water at 25°C. If the vapor pressure of water at 25°C is 23.8 torr, what is the partial pressure of the gas?

A. 1.00 atm

Correct B. 0.975 atm

C. 0.950 atm

D. 0.925 atm

Correct Answer: B

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Question 8

A 25.0 mL sample of a 0.100 M solution of NaOH is mixed with 25.0 mL of a 0.100 M solution of HCl. 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 9

A 1.00 L sample of a gas at 25°C and 1.00 atm is collected over water at 25°C. If the vapor pressure of water at 25°C is 23.8 torr, what is the partial pressure of the gas?

A. 1.00 atm

Correct B. 0.975 atm

C. 0.950 atm

D. 0.925 atm

Correct Answer: B

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Question 10

A 2.50 L sample of a gas at 25°C and 1.00 atm is collected over water at 25°C. If the vapor pressure of water at 25°C is 23.8 torr, what is the partial pressure of the gas?

A. 1.00 atm

Correct B. 0.975 atm

C. 0.950 atm

D. 0.925 atm

Correct Answer: B

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Question 11

Determine the molar solubility of Ag2CrO4 in 0.1 M NaCl solution, given that the solubility product cons\tant (Ksp) for Ag2CrO4 is 1.1 × 10^\( -12 \).

A. 1.0 × 10^\( -6 \) M

Correct B. 1.5 × 10^\( -6 \) M

C. 2.0 × 10^\( -6 \) M

D. 3.0 × 10^\( -6 \) M

Correct Answer: B

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Question 12

A 2.50-g sample of a metal (M) is dissolved in 25.0 mL of 0.100 M HCl. The resulting solution is then titrated with 0.100 M NaOH. If the volume of NaOH required to reach the equivalence point is 12.5 mL, what is the identity of the metal (M)?

A. Zn

B. Fe

Correct C. Ni

D. Cu

Correct Answer: C

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Question 13

The reaction between H2 and O2 is catalyzed by Pt. The rate cons\tant (k) for this reaction is 2.5 × 10^\( -3 \) s^\( -1 \) at 298 K. If the initial concentrations of H2 and O2 are 0.100 M and 0.0500 M, respectively, what is the rate of reaction after 5.00 s?

A. 1.25 × 10^\( -5 \) M s^\( -1 \)

B. 2.50 × 10^\( -5 \) M s^\( -1 \)

Correct C. 3.75 × 10^\( -5 \) M s^\( -1 \)

D. 5.00 × 10^\( -5 \) M s^\( -1 \)

Correct Answer: C

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Question 14

A 0.100 M solution of NaOH is titrated with 0.100 M HCl. If the initial volume of NaOH is 25.0 mL and the final volume is 50.0 mL, what is the pH of the resulting solution?

A. 7.00

Correct B. 8.00

C. 9.00

D. 10.0

Correct Answer: B

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Question 15

A 0.100 M solution of HCl is titrated with 0.100 M NaOH. If the initial volume of HCl is 25.0 mL and the final volume is 50.0 mL, what is the pH of the resulting solution?

A. 1.00

B. 2.00

C. 3.00

Correct D. 4.00

Correct Answer: D

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Question 16

Determine the number of moles of oxygen gas (O2) produced at s\tandard temperature and pressure (STP) from the complete combustion of 2.5 g of propane (C3H8).

A. 0.25 mol

Correct B. 0.50 mol

C. 0.75 mol

D. 1.00 mol

Correct Answer: B

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Question 17

A 0.500 M solution of NaOH is mixed with a 0.500 M solution of HCl. What is the resulting pH after the reaction is complete?

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 18

A 2.00 L flask contains 0.500 atm of N2 and 0.500 atm of O2 at 25°C. What is the partial pressure of O2 after 0.500 atm of N2 is removed?

A. 0.250 atm

Correct B. 0.500 atm

C. 0.750 atm

D. 1.00 atm

Correct Answer: B

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Question 19

A 0.500 M solution of HCl is mixed with a 0.500 M solution of NaOH. What is the resulting concentration of HCl after the reaction is complete?

A. 0.250 M

Correct B. 0.500 M

C. 0.750 M

D. 1.00 M

Correct Answer: B

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Question 20

A 2.00 L flask contains 0.500 atm of N2 and 0.500 atm of O2 at 25°C. What is the total pressure of the gas mixture?

A. 0.500 atm

B. 1.00 atm

C. 1.50 atm

Correct D. 2.00 atm

Correct Answer: D

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Question 21

Determine the s\tandard electrode potential of the cell represented by the equation: Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s). Given that the s\tandard electrode potential of Zn²⁺/Zn is -0.76 V and that of Cu²⁺/Cu is +0.34 V.

Correct A. +0.10 V

B. -0.10 V

C. +0.50 V

D. -0.50 V

Correct Answer: A

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Question 22

A 100 mL sample of a solution containing 0.5 M NaCl is electrolyzed u\sing a current of 0.5 A for 10 minutes. Calculate the mass of Cl₂ gas produced at the anode.

A. 0.15 g

Correct B. 0.30 g

C. 0.45 g

D. 0.60 g

Correct Answer: B

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Question 23

The rate cons\tant (k) of a first-order reaction is given by the equation: ln\( [A]t/[A]0 \) = -kt. If the half-life of the reaction is 10 minutes, calculate the rate cons\tant (k) if the initial concentration of the reac\tant is 0.5 M.

Correct A. 0.069 min⁻¹

B. 0.069 hr⁻¹

C. 0.069 s⁻¹

D. 0.069 d⁻¹

Correct Answer: A

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Question 24

A 2.0 L sample of a solution containing 0.5 M H₂SO₄ is titrated with 0.5 M NaOH. Calculate the volume of NaOH required to reach the equivalence point.

A. 1.0 L

Correct B. 1.5 L

C. 2.0 L

D. 2.5 L

Correct Answer: B

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Question 25

A 100 mL sample of a solution containing 0.5 M NH₃ is treated with 10 mL of 0.5 M HCl. Calculate the pH of the resulting solution.

A. 4.0

Correct B. 5.0

C. 6.0

D. 7.0

Correct Answer: B

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