POST UTME UNIBEN 2025 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
Determine the number of moles of CO2 produced when 2.5 g of calcium carbonate (CaCO3) is completely decomposed at cons\tant pressure and temperature.
A. 0.05 mol
B. 0.10 mol
C. 0.15 mol
D. 0.20 mol
Question 2
A 2.5 M solution of HCl is electrolyzed u\sing a platinum electrode. What is the mass of Cl2 gas produced at the anode in 2 hours?
A. 0.25 g
B. 0.50 g
C. 1.00 g
D. 2.00 g
Question 3
What is the oxidation state of sulfur in the compound SO2Cl2?
A. +4
B. +2
C. +6
D. +8
Question 4
A 2.0 L flask contains 0.5 mol of an ideal gas at 25°C. What is the pressure of the gas in atm, given that the gas cons\tant R = 0.0821 L atm/mol K?
A. 0.5 atm
B. 1.0 atm
C. 1.5 atm
D. 2.0 atm
Question 5
The rate of a chemical reaction is affected by several factors, including the concentration of reac\tants, temperature, and surface area. Which of the following is an example of a factor that increases the rate of a chemical reaction?
A. Increa\sing the concentration of reac\tants
B. Decrea\sing the temperature
C. Increa\sing the surface area of reac\tants
D. Decrea\sing the pressure
Question 6
Determine the number of moles of oxygen gas (O2) required to completely combust 2.5 moles of propane (C3H8) according to the balanced equation: C3H8 + 5O2 → 3CO2 + 4H2O.
A. 1.25
B. 2.5
C. 3.75
D. 5.0
Question 7
A sample of hydrogen gas (H2) is collected over water at a temperature of 20°C and a pressure of 1 atm. If the volume of the gas is 2.5 L, calculate the partial pressure of the hydrogen gas.
A. 0.5 atm
B. 0.6 atm
C. 0.7 atm
D. 0.8 atm
Question 8
A sample of oxygen gas (O2) is collected over water at a temperature of 20°C and a pressure of 1 atm. If the volume of the gas is 2.5 L, calculate the partial pressure of the oxygen gas.
A. 0.5 atm
B. 0.6 atm
C. 0.7 atm
D. 0.8 atm
Question 9
The atomic radius of an atom is defined as the dis\tance from the nucleus to the outermost electron in a neutral atom. Which of the following statements is true about the atomic radius of an atom?
A. The atomic radius of an atom decreases as the atomic number increases.
B. The atomic radius of an atom increases as the atomic number increases.
C. The atomic radius of an atom remains cons\tant for all elements.
D. The atomic radius of an atom is indep\endent of the atomic number.
Question 10
A polymer has a molecular weight of 50,000 g/mol and a degree of polymerization of 500. What is the molar mass of the repeating unit?
A. 100
B. 200
C. 500
D. 1000
Question 11
The entropy change (ΔS) for a reaction is given by the equation ΔS = ΔH/T. If the enthalpy change (ΔH) for a reaction is -120 kJ/mol and the temperature (T) is 298 K, calculate the entropy change (ΔS) in J/mol·K.
A. 400 J/mol·K
B. 500 J/mol·K
C. 600 J/mol·K
D. 700 J/mol·K
Question 12
A gas is confined to a container with a volume of 2.5 L. If the temperature of the gas is increased from 20°C to 50°C, calculate the new volume of the gas, assuming the pressure remains cons\tant.
A. 3.5 L
B. 4.0 L
C. 4.5 L
D. 5.0 L
Question 13
A 5.0 L flask contains 2.0 mol of an ideal gas at 30°C. What is the pressure of the gas in atm, given that the gas cons\tant R = 0.0821 L atm/mol K?
A. 1.0 atm
B. 1.5 atm
C. 2.0 atm
D. 2.5 atm
Question 14
The boiling point of a subs\tance is the temperature at which the vapor pressure of the subs\tance equals the surrounding pressure. Which of the following is an example of a subs\tance with a high boiling point?
A. H2O
B. CO2
C. CH4
D. O2
Question 15
The solubility of a subs\tance is the maximum amount of the subs\tance that can dissolve in a given amount of solvent at a particular temperature. Which of the following is an example of a subs\tance with a high solubility?
A. NaCl
B. CaCO3
C. H2O
D. CO2

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