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POST UTME GREENFIELD UNIVERSITY 2025 Chemistry | Objective

Are you preparing for POST UTME GREENFIELD UNIVERSITY exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2025 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 acetic acid (CH3COOH) at 25°C.

A. 3.5

Correct B. 4.5

C. 5.5

D. 6.5

Correct Answer: B

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Question 2

What is the molar mass of a compound composed of 40% carbon and 60% oxygen by mass?

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 3

A 2.5 L sample of a 0.2 M solution of NaOH is titrated with 0.1 M HCl. What is the pH of the resulting solution?

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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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 measure the pH of the solution

Correct Answer: A

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Question 5

A 0.1 M solution of NaOH is titrated with 0.1 M HCl. 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 6

Determine the pH of a 0.1 M solution of HCl.

Correct A. 1

B. 2

C. 3

D. 4

Correct Answer: A

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Question 7

A 2.5 g sample of a metal carbonate is treated with 20 cm³ of 0.5 M HCl. If 10 cm³ of the excess acid is titrated with 0.1 M NaOH, calculate the molar mass of the metal.

A. 50

B. 75

Correct C. 100

D. 125

Correct Answer: C

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Question 8

The diagram below shows a cell with a potential difference of 1.5 V. If the internal resis\tance of the cell is 5 Ω, calculate the current flowing through the circuit.

A. 0.3

Correct B. 0.5

C. 0.7

D. 0.9

Correct Answer: B

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Question 9

A solution containing 0.5 g of NaCl is diluted to 250 cm³. If 20 cm³ of the solution is titrated with 0.1 M AgNO₃, calculate the concentration of the solution.

A. 0.1

B. 0.2

Correct C. 0.3

D. 0.4

Correct Answer: C

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Question 10

A 2.0 g sample of a metal oxide is heated in a Bunsen flame. If 0.5 g of the metal is obtained, calculate the percentage yield.

A. 50

B. 60

Correct C. 70

D. 80

Correct Answer: C

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Question 11

The reaction between sodium hydroxide (NaOH) and hydrochloric acid (HCl) is highly exothermic. Calculate the s\tandard enthalpy change (ΔH°) for the reaction, given that the s\tandard enthalpy of formation (ΔH°f) for NaOH is -469.8 kJ/mol and for HCl is -92.3 kJ/mol.

A. NaOH + HCl → NaCl + H2O

Correct B. -377.5 kJ/mol

C. NaOH + HCl → NaCl + H2O + heat

D. The reaction is \endothermic

Correct Answer: B

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Question 12

A 0.5 M solution of calcium chloride (CaCl2) is prepared by dissolving 0.25 mol of CaCl2 in 0.5 L of water. What is the concentration of calcium ions \( Ca2+ \) in the solution?

Correct A. 0.25 M

B. 0.5 M

C. 1.0 M

D. 1.5 M

Correct Answer: A

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Question 13

The half-life of a radioactive subs\tance is 5 years. If 100 g of the subs\tance is initially present, how much of the subs\tance will remain after 20 years?

Correct A. 12.5 g

B. 25 g

C. 50 g

D. 100 g

Correct Answer: A

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Question 14

The reaction between hydrogen gas (H2) and oxygen gas (O2) is highly exothermic. Write a balanced chemical equation for the reaction, including the s\tandard enthalpy change (ΔH°) for the reaction.

Correct A. 2H2 + O2 → 2H2O, \u0394H° = -572 kJ/mol

B. H2 + O2 → H2O, \u0394H° = -286 kJ/mol

C. 2H2 + O2 → 2H2O, \u0394H° = -286 kJ/mol

D. H2 + O2 → H2O, \u0394H° = -572 kJ/mol

Correct Answer: A

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Question 15

A 0.1 M solution of sodium hydroxide (NaOH) is prepared by dissolving 0.01 mol of NaOH in 0.1 L of water. What is the concentration of hydroxide ions \( OH- \) in the solution?

Correct A. 0.01 M

B. 0.1 M

C. 0.5 M

D. 1.0 M

Correct Answer: A

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Question 16

A polymer is formed by the condensation reaction between a diol and a diacid. If 2.5 g of diol and 3.2 g of diacid are used, and the molecular weight of the diol is 62 g/mol, calculate the number of moles of the polymer formed.

A. 0.04 mol

B. 0.06 mol

Correct C. 0.08 mol

D. 0.1 mol

Correct Answer: C

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Question 17

A solution of ethanol (C2H5OH) is prepared by dissolving 25.0 g of ethanol in 100.0 g of water. Calculate the mole \fraction of ethanol in the solution.

A. 0.15

Correct B. 0.25

C. 0.35

D. 0.45

Correct Answer: B

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Question 18

A 2.0 M solution of sodium hydroxide (NaOH) is prepared by dissolving 40.0 g of NaOH in 1.0 L of water. Calculate the pH of the solution.

A. 12

Correct B. 13

C. 14

D. 15

Correct Answer: B

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Question 19

A metal rod of length 20.0 cm and radius 1.0 cm is heated to a temperature of 100°C. Calculate the energy required to raise the temperature of the rod to 200°C.

A. 1600

B. 3200

Correct C. 4800

D. 6400

Correct Answer: C

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Question 20

A 2.0 M solution of hydrochloric acid (HCl) is prepared by dissolving 40.0 g of HCl in 1.0 L of water. Calculate the concentration of HCl in the solution.

A. 1.1

Correct B. 1.2

C. 1.3

D. 1.4

Correct Answer: B

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Question 21

A metal rod of length 20.0 cm and radius 1.0 cm is heated to a temperature of 100°C. Calculate the energy required to raise the temperature of the rod to 200°C.

A. 1600

B. 3200

C. 4800

D. 6400

Correct Answer: VIEW ANSWER

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Question 22

Determine the equilibrium cons\tant (Kc) for the reaction: 2NO(g) + O2(g) ⇌ 2NO2(g), given that [NO] = 0.5 M, [O2] = 0.2 M, and [NO2] = 0.8 M.

Correct A. \( K_c = \frac{[NO_2]^2}{[NO]^2 [O_2]} \)

B. \( K_c = \frac{[NO_2]}{[NO]^2 [O_2]} \)

C. \( K_c = \frac{[NO]^2 [O_2]}{[NO_2]^2} \)

D. \( K_c = \frac{[NO]^2 [O_2]^2}{[NO_2]^2} \)

Correct Answer: A

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Question 23

A 0.5 M solution of NaOH is titrated with 0.1 M HCl. Calculate the pH of the solution after 25 mL of HCl has been added.

A. \( pH = 12.5 \)

Correct B. \( pH = 11.5 \)

C. \( pH = 10.5 \)

D. \( pH = 9.5 \)

Correct Answer: B

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Question 24

A sample of air contains 20% O2, 70% N2, and 10% CO2 by volume. Calculate the partial pressure of CO2 in a sample of air at 1 atm.

Correct A. \( P_{CO_2} = 0.1 \) atm

B. \( P_{CO_2} = 0.2 \) atm

C. \( P_{CO_2} = 0.3 \) atm

D. \( P_{CO_2} = 0.4 \) atm

Correct Answer: A

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Question 25

A 2 M solution of H2SO4 is mixed with 1 M solution of NaOH. Calculate the concentration of the resulting solution.

A. ( 1.5 ) M

B. ( 2.5 ) M

Correct C. ( 3.5 ) M

D. ( 4.5 ) M

Correct Answer: C

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