POST UTME LASU 2024 Chemistry | Objective

Are you preparing for POST UTME LASU exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2024 Chemistry (Objective) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1
Determine the number of moles of oxygen gas (O2) produced at s\tandard temperature and pressure (STP) when 2.5 moles of hydrogen gas (H2) react with oxygen gas according to the balanced equation: 2H2 + O2 → 2H2O.
Correct A. 1.25 moles
B. 2.5 moles
C. 5 moles
D. 10 moles

Correct Answer: A

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Question 2
A 2.5 M solution of sodium hydroxide (NaOH) is titrated with a 1.0 M solution of hydrochloric acid (HCl). If 25 mL of the acid is required to reach the equivalence point, what is the volume of the base solution required to reach the equivalence point?
Correct A. 12.5 mL
B. 25 mL
C. 50 mL
D. 100 mL

Correct Answer: A

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Question 3
A redox reaction involves the oxidation of copper metal (Cu) to copper(II) ions \( Cu2+ \) and the reduction of silver ions \( Ag+ \) to silver metal (Ag). Write the balanced half-equations for the oxidation and reduction reactions.
A. Oxidation: Cu → Cu2+ + 2e-; Reduction: Ag+ + e- → Ag
B. Oxidation: Cu → Cu2+ + e-; Reduction: Ag+ + 2e- → Ag
Correct C. Oxidation: Cu → Cu2+ + 2e-; Reduction: Ag+ + e- → Ag
D. Oxidation: Cu → Cu2+ + e-; Reduction: Ag+ + 2e- → Ag

Correct Answer: C

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Question 4
A 10% solution of sodium chloride (NaCl) is prepared by dissolving 10 g of NaCl in 90 g of water. What is the molarity of the solution?
Correct A. 0.1 M
B. 0.5 M
C. 1.0 M
D. 5.0 M

Correct Answer: A

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Question 5
A 2.0 L container is filled with 1.5 moles of an ideal gas at a temperature of 300 K. What is the pressure of the gas in the container?
A. 2.0 atm
Correct B. 3.0 atm
C. 4.0 atm
D. 5.0 atm

Correct Answer: B

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Question 6
A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the pH of the solution after the addition of 25.0 mL of NaOH.
A. 2.00
Correct B. 3.00
C. 4.00
D. 5.00

Correct Answer: B

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Question 7
The diagram below shows a titration setup. Identify the part labeled A.
Correct A. Burette
B. Beaker
C. Test tube
D. Circuit

Correct Answer: A

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Question 8
A metal (X) reacts with hydrochloric acid (HCl) to produce a salt (Y) and hydrogen gas. The reaction is as follows: \[ \text{X} + 2\text{HCl} \rightarrow \text{Y} + \text{H}_2 \]. Identify the metal (X) and the salt (Y).
Correct A. Zn, ZnCl2
B. Fe, FeCl2
C. Cu, CuCl2
D. Ag, AgCl

Correct Answer: A

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Question 9
A 10.0 g sample of a polymer is dissolved in 100.0 mL of a solvent. The solution has a vis\cosity of 0.50 Pa·s. Calculate the molar mass of the polymer.
A. 1000 g/mol
B. 5000 g/mol
Correct C. 10000 g/mol
D. 20000 g/mol

Correct Answer: C

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Question 10
The diagram below shows a phase diagram for a binary system. Identify the region labeled A.
Correct A. Liquid-liquid equilibrium
B. Solid-liquid equilibrium
C. Liquid-vapor equilibrium
D. Solid-vapor equilibrium

Correct Answer: A

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Question 11
Determine the pH of a 0.1 M solution of HCl. Assume that the dissociation of HCl is complete.
A. 1
B. 2
C. 3
Correct D. 4

Correct Answer: D

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Question 12
A sample of a hydrocarbon has a molecular formula of C5H12. What is the type of hydrocarbon?
Correct A. Alkane
B. Alkene
C. Alkyne
D. Aromatic hydrocarbon

Correct Answer: A

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Question 13
A 25 mL sample of a solution containing 0.1 M HCl is titrated with 0.1 M NaOH. Calculate the volume of NaOH required to reach the equivalence point.
A. 12.5 mL
B. 25 mL
Correct C. 37.5 mL
D. 50 mL

Correct Answer: C

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Question 14
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 filter the solution

Correct Answer: A

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Question 15
A sample of a gas has a volume of 2.5 L at a pressure of 1.5 atm and a temperature of 298 K. What is the new volume of the gas at a pressure of 3.0 atm and a temperature of 323 K?
A. 3.2 L
Correct B. 3.5 L
C. 3.8 L
D. 4.0 L

Correct Answer: B

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Question 16
Determine the pH of a solution containing 0.1 M HCl and 0.2 M NaOH.
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 17
A 0.5 M solution of a weak acid HA has a pH of 4.5. Calculate the value of Ka.
A. 1.0 x 10^\( -5 \)
Correct B. 1.0 x 10^\( -4 \)
C. 1.0 x 10^\( -3 \)
D. 1.0 x 10^\( -2 \)

Correct Answer: B

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Question 18
The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of combustion of 1 mole of methane (CH4(g)) at 298 K.
Correct A. -890.3 kJ/mol
B. -890.6 kJ/mol
C. -890.9 kJ/mol
D. -891.1 kJ/mol

Correct Answer: A

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Question 19
A 2.0 M solution of a weak base B has a pOH of 10.5. Calculate the value of Kb.
A. 1.0 x 10^\( -5 \)
B. 1.0 x 10^\( -4 \)
Correct C. 1.0 x 10^\( -3 \)
D. 1.0 x 10^\( -2 \)

Correct Answer: C

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Question 20
A 0.5 M solution of a weak acid HA has a pH of 4.5. Calculate the value of Ka.
A. 1.0 x 10^\( -5 \)
Correct B. 1.0 x 10^\( -4 \)
C. 1.0 x 10^\( -3 \)
D. 1.0 x 10^\( -2 \)

Correct Answer: B

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Question 21
The reaction of nitrogen dioxide with water produces nitric acid and nitric oxide. Write the balanced chemical equation for this reaction.
A. \text{NO}_2 + \text{H}_2\text{O} \rightarrow \text{HNO}_3 + \text{NO}_2
B. \text{NO}_2 + \text{H}_2\text{O} \rightarrow \text{HNO}_3 + \text{O}_2
Correct C. \text{NO}_2 + \text{H}_2\text{O} \rightarrow \text{HNO}_3 + \text{NO}
D. \text{NO}_2 + \text{H}_2\text{O} \rightarrow \text{HNO}_3 + \text{H}_2

Correct Answer: C

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Question 22
The boiling point of a subs\tance is the temperature at which the vapor pressure of the subs\tance equals the surrounding pressure. What is the boiling point of water at s\tandard atmospheric pressure?
Correct A. 373.15 K
B. 373.15 °C
C. 100 °C
D. 100 K

Correct Answer: A

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Question 23
The reaction of sodium hydroxide with hydrochloric acid produces sodium chloride and water. Write the balanced chemical equation for this reaction.
Correct A. \text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O}
B. \text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2
C. \text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{O}_2
D. \text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O}_2

Correct Answer: A

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Question 24
The reaction of sulfuric acid with sodium hydroxide produces sodium sulfate and water. Write the balanced chemical equation for this reaction.
Correct A. \text{H}_2\text{SO}_4 + 2\text{NaOH} \rightarrow \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O}
B. \text{H}_2\text{SO}_4 + 2\text{NaOH} \rightarrow \text{Na}_2\text{SO}_4 + \text{H}_2
C. \text{H}_2\text{SO}_4 + 2\text{NaOH} \rightarrow \text{Na}_2\text{SO}_4 + \text{O}_2
D. \text{H}_2\text{SO}_4 + 2\text{NaOH} \rightarrow \text{Na}_2\text{SO}_4 + \text{H}_2\text{O}_2

Correct Answer: A

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Question 25
The reaction of nitric acid with sodium hydroxide produces sodium nitrate and water. Write the balanced chemical equation for this reaction.
Correct A. \text{HNO}_3 + \text{NaOH} \rightarrow \text{NaNO}_3 + \text{H}_2\text{O}
B. \text{HNO}_3 + \text{NaOH} \rightarrow \text{NaNO}_3 + \text{H}_2
C. \text{HNO}_3 + \text{NaOH} \rightarrow \text{NaNO}_3 + \text{O}_2
D. \text{HNO}_3 + \text{NaOH} \rightarrow \text{NaNO}_3 + \text{H}_2\text{O}_2

Correct Answer: A

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