POST UTME LASU 2024 Chemistry | Objective

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Question 1 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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 View Details
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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