POST UTME LASU 2024 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
The reaction of nitrogen dioxide with water is an example of a reaction that involves the formation of a new compound through the interaction of two reac\tants. Which of the following is the correct equation for this reaction?
A. \( 2NO_2 + H_2O \rightarrow HNO_3 + NO \)
B. \( 2NO_2 + H_2O \rightarrow HNO_3 + NO_2 \)
C. \( 2NO_2 + H_2O \rightarrow HNO_3 + H_2O \)
D. \( 2NO_2 + H_2O \rightarrow NO_3^- + H^+ \)
Question 2
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^\( -5 \)
B. 1.0 x 10^\( -4 \)
C. 1.0 x 10^\( -3 \)
D. 1.0 x 10^\( -2 \)
Question 3
The half-life of a radioactive subs\tance is 10 years. If the initial amount of the subs\tance is 100 g, what is the amount remaining after 20 years?
A. 25 g
B. 50 g
C. 75 g
D. 100 g
Question 4
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.
A. -890.3 kJ/mol
B. -890.6 kJ/mol
C. -890.9 kJ/mol
D. -891.1 kJ/mol
Question 5
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
C. 37.5 mL
D. 50 mL
Question 6
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
C. Oxidation: Cu → Cu2+ + 2e-; Reduction: Ag+ + e- → Ag
D. Oxidation: Cu → Cu2+ + e-; Reduction: Ag+ + 2e- → Ag
Question 7
The s\tandard enthalpy of formation of carbon dioxide is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of carbon monoxide?
A. -110.5 kJ/mol
B. -393.5 kJ/mol
C. 110.5 kJ/mol
D. 393.5 kJ/mol
Question 8
The diagram below shows a phase diagram for a binary system. Identify the region labeled A.
A. Liquid-liquid equilibrium
B. Solid-liquid equilibrium
C. Liquid-vapor equilibrium
D. Solid-vapor equilibrium
Question 9
The s\tandard enthalpy of formation of H2O(l) is -285.8 kJ/mol. What is the s\tandard enthalpy of formation of H2(g)?
A. -285.8 kJ/mol
B. 0 kJ/mol
C. 285.8 kJ/mol
D. 572.8 kJ/mol
Question 10
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?
A. 373.15 K
B. 373.15 °C
C. 100 °C
D. 100 K
Question 11
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?
A. 0.1 M
B. 0.5 M
C. 1.0 M
D. 5.0 M
Question 12
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
B. 3.0 atm
C. 4.0 atm
D. 5.0 atm
Question 13
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
B. 3.5 L
C. 3.8 L
D. 4.0 L
Question 14
The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of CO(g)?
A. -110.5 kJ/mol
B. -393.5 kJ/mol
C. -74.8 kJ/mol
D. 74.8 kJ/mol
Question 15
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?
A. 12.5 mL
B. 25 mL
C. 50 mL
D. 100 mL

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