POST UTME PAN-ATLANTIC UNIVERSITY 2025 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
A solution of hydrochloric acid (HCl) is prepared by dissolving 25 g of the acid in 250 mL of water. What is the concentration of the solution in g/L?
A. 100 g/L
B. 110 g/L
C. 120 g/L
D. 130 g/L
Question 2
A 25.0 mL sample of 0.150 M HCl is mixed with a 25.0 mL sample of 0.150 M NaOH. What is the concentration of the resulting solution?
A. 0.0750 M
B. 0.150 M
C. 0.225 M
D. 0.300 M
Question 3
A 2.50 g sample of a compound containing only C, H, and O is analyzed by combustion. The CO2 produced is collected and found to have a mass of 1.25 g. The H2O produced is collected and found to have a mass of 0.500 g. What is the empirical formula of the compound?
A. C2H4O2
B. C2H6O
C. C3H6O
D. C3H8O
Question 4
A sample of oxygen (O2) is collected over water at a temperature of 20°C and a pressure of 1 atm. What is the volume of the gas at STP?
A. 2.0 L
B. 2.5 L
C. 3.0 L
D. 3.5 L
Question 5
A 2.00 g sample of a subs\tance is dissolved in 100.0 mL of water. What is the molarity of the solution?
A. M = 0.100 M
B. M = 0.200 M
C. M = 0.300 M
D. M = 0.400 M
Question 6
Calculate the s\tandard enthalpy change \( ΔH^circ \) for the reaction: 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s). The s\tandard enthalpy of formation \( ΔH^circ_f \) values are: ΔH^circ_f(Al2O3(s)) = -1675.7 kJ/mol, ΔH^circ_f(Al(s)) = 0 kJ/mol, ΔH^circ_f(Fe(s)) = 0 kJ/mol, and ΔH^circ_f(Fe2O3(s)) = -824.2 kJ/mol.
A. 0 kJ/mol
B. -1675.7 kJ/mol
C. 1675.7 kJ/mol
D. 824.2 kJ/mol
Question 7
A metal (M) reacts with oxygen (O2) to form a basic oxide (MO). If 2.5 g of the metal is heated in air, and 1.5 g of the oxide is formed, what is the percentage yield of the reaction?
A. 60%
B. 70%
C. 80%
D. 90%
Question 8
A 5.00-g sample of a non-metallic compound is dissolved in 100 mL of a solvent. The molar mass of the compound is 200 g/mol. Calculate the concentration of the compound in the solution.
A. 0.0500 M
B. 0.100 M
C. 0.200 M
D. 0.500 M
Question 9
In a reaction between sodium (Na) and chlorine (Cl2), what is the expected product?
A. Sodium chloride (NaCl)
B. Sodium oxide (Na2O)
C. Chlorine gas (Cl2)
D. Sodium hydroxide (NaOH)
Question 10
A metal (M) reacts with oxygen to form a basic oxide (MO). The reaction is: 4M + 3O2 → 2MO. If 2.50 g of M reacts with 1.50 g of O2, what is the mass of M used?
A. 2.50 g
B. 3.75 g
C. 4.25 g
D. 5.00 g
Question 11
A metal (M) has an atomic radius of 250 pm. If the metal forms a +3 ion, what is the radius of the ion?
A. 80 pm
B. 100 pm
C. 120 pm
D. 150 pm
Question 12
Determine the s\tandard Gibbs free energy change (ΔG°) for the reaction: 2Ag+(aq) + 2I-(aq) → 2Ag(s) + I2(s) at 298 K, given that the s\tandard enthalpy change (ΔH°) is -187.2 kJ/mol and the s\tandard entropy change (ΔS°) is -278.0 J/mol·K.
A. -187.2 kJ/mol
B. -187.2 kJ/mol + 278.0 J/mol·K
C. -187.2 kJ/mol - 278.0 J/mol·K
D. -187.2 kJ/mol + 278.0 J/mol·K
Question 13
The rate cons\tant for the decomposition of a certain compound is 2.50 × 10⁻² s⁻¹ at 25°C. If the initial concentration of the compound is 0.100 M, calculate the concentration of the compound after 5.00 minutes.
A. 0.0500 M
B. 0.0750 M
C. 0.100 M
D. 0.125 M
Question 14
A solution of sodium chloride (NaCl) is prepared by dissolving 35 g of the salt in 250 mL of water. What is the concentration of the solution in g/L?
A. 140 g/L
B. 150 g/L
C. 160 g/L
D. 170 g/L
Question 15
A 2.00 g sample of a subs\tance is burned in a bomb calorimeter. The temperature of the calorimeter increases by 10.0 K. What is the heat of combustion of the subs\tance?
A. \Delta H = -20.0 kJ
B. \Delta H = -30.0 kJ
C. \Delta H = -40.0 kJ
D. \Delta H = -50.0 kJ

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