POST UTME OAU 2019 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
A 2.50 g sample of a non-metallic element is found to have a mass of 1.25 g after being heated in a Bunsen burner. What is the percentage increase in mass?
A. 25.0%
B. 50.0%
C. 75.0%
D. 100.0%
Question 2
A 1.0 M solution of Fe2+ is electrolyzed for 2.0 hours. Calculate the mass of Fe deposited at the cathode.
A. 0.1 g
B. 0.2 g
C. 0.3 g
D. 0.4 g
Question 3
The reaction of methane with oxygen to form carbon dioxide and water is represented by the equation: CH4 + 2O2 → CO2 + 2H2O. What is the value of ΔH for this reaction, given that ΔH for the formation of CO2 is -393.5 kJ/mol and ΔH for the formation of H2O is -285.8 kJ/mol?
A. -890.1 kJ/mol
B. -393.5 kJ/mol
C. -285.8 kJ/mol
D. -74.8 kJ/mol
Question 4
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. -74.8 kJ/mol
D. -74.8 kJ/mol
Question 5
A 10% solution of sulfuric acid (H2SO4) is made by dissolving 10 g of the acid in 90 g of water. Calculate the molarity of the solution.
A. 0.1 M
B. 0.5 M
C. 1.0 M
D. 2.0 M
Question 6
A polymer of ethylene glycol (C2H6O2) has a molecular weight of 180 g/mol. Calculate the number of repeating units in the polymer.
A. 5
B. 10
C. 15
D. 20
Question 7
A 1.0 M solution of hydrochloric acid is prepared by dissolving 36.5 g of hydrochloric acid in water to make 1 L of solution. What is the concentration of hydrogen ions in the solution?
A. 0.5 M
B. 1.0 M
C. 1.5 M
D. 2.0 M
Question 8
Determine the number of moles of CO2 produced from the complete combustion of 2.5 g of propane (C3H8) according to the balanced equation: C3H8 + 5O2 → 3CO2 + 4H2O.
A. 0.25 mol
B. 0.5 mol
C. 0.75 mol
D. 1.0 mol
Question 9
The s\tandard enthalpy of formation of H2O(l) is -285.8 kJ/mol. Calculate the s\tandard enthalpy of vaporization of 1.00 mol of water at 373 K.
A. 40.7 kJ
B. 41.1 kJ
C. 41.5 kJ
D. 42.0 kJ
Question 10
The half-life of a radioactive subs\tance is 5.00 days. If a sample initially contains 100.0 g of the subs\tance, what is the mass remaining after 20.0 days?
A. 25.0 g
B. 50.0 g
C. 75.0 g
D. 100.0 g
Question 11
The reaction of zinc metal with copper(II) sulfate solution is represented by the equation: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s). What is the oxidation state of copper in the reac\tant and product?
A. +2 in reac\tant, +2 in product
B. +2 in reac\tant, -2 in product
C. -2 in reac\tant, +2 in product
D. -2 in reac\tant, -2 in product
Question 12
A 2.50 g sample of a non-metallic oxide of nitrogen is decomposed by heating with graphite. The volume of nitrogen gas produced at 25°C and 1 atm is 2.50 L. Calculate the molar mass of the oxide.
A. 60 g/mol
B. 80 g/mol
C. 100 g/mol
D. 120 g/mol
Question 13
The molar mass of a gas is 44.0 g/mol. If 2.50 g of the gas occupies a volume of 22.4 L at 298 K, what is the gas?
A. CO2
B. O2
C. N2
D. H2
Question 14
A 0.5 M solution of NaOH is prepared by dissolving 10 g of NaOH in water to make 1 L of solution. Calculate the concentration of the solution in mol/L.
A. 0.1 M
B. 0.2 M
C. 0.5 M
D. 1.0 M
Question 15
A 25 mL sample of 0.2 M H2SO4 is titrated with 0.2 M NaOH. Calculate the volume of NaOH required to reach the equivalence point.
A. 10 mL
B. 20 mL
C. 30 mL
D. 40 mL

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