POST UTME ACHIEVERS UNIVERSITY 2023 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
Determine the number of moles of oxygen gas (O2) produced at STP when 2.50 g of potassium chlorate (KClO3) decomposes according to the equation: 2KClO3(s) → 2KCl(s) + 3O2(g).
A. 0.125 mol
B. 0.250 mol
C. 0.500 mol
D. 1.00 mol
Question 2
A 2.0 M solution of H2SO4 is titrated with 0.5 M NaOH. If 20 mL of NaOH is required to reach the equivalence point, calculate the number of moles of H2SO4 present in the solution.
A. 0.01 mol
B. 0.0125 mol
C. 0.015 mol
D. 0.0175 mol
Question 3
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. 0 kJ/mol
B. 10 kJ/mol
C. 20 kJ/mol
D. 30 kJ/mol
Question 4
The half-life of a radioactive subs\tance is 5 years. If 100 g of the subs\tance is initially present, what mass of the subs\tance will remain after 15 years?
A. 12.5 g
B. 25 g
C. 50 g
D. 100 g
Question 5
The rate cons\tant of a first-order reaction is given by the equation k = Ae^{-Ea/RT}. If the rate cons\tant at 25°C is 0.05 s^{-1} and at 50°C is 0.2 s^{-1}, calculate the activation energy (Ea) of the reaction.
A. 50000 J/mol
B. 60000 J/mol
C. 70000 J/mol
D. 80000 J/mol
Question 6
A 2.0 M solution of hydrochloric acid is prepared by dissolving 40 g of hydrochloric acid in 100 mL of water. What is the concentration of the solution in terms of molarity?
A. 2.0 M
B. 4.0 M
C. 6.0 M
D. 8.0 M
Question 7
A sample of nitrogen gas occupies 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 if the pressure is increased to 3.0 atm at cons\tant temperature?
A. 1.5 L
B. 2.5 L
C. 3.5 L
D. 4.5 L
Question 8
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. -130.5 kJ/mol
C. -150.5 kJ/mol
D. -170.5 kJ/mol
Question 9
A 0.5 M solution of HCl is prepared by dissolving 25 g of HCl in 1 L of water. Calculate the pH of the solution.
A. 0.5
B. 1.0
C. 1.5
D. 2.0
Question 10
A 10.0 g sample of a compound containing only carbon and hydrogen is analyzed by combustion. The volume of CO2 produced is 22.5 mL at 25°C and 1 atm. What is the empirical formula of the compound?
A. CH4
B. C2H4
C. C3H6
D. C4H8
Question 11
A 2.5 L flask contains 0.5 mol of an ideal gas at 25°C. Calculate the work done by the gas when it expands to 5 L against a cons\tant external pressure of 1.5 atm.
A. 1.9 kJ
B. 2.1 kJ
C. 2.3 kJ
D. 2.5 kJ
Question 12
A 0.5 M solution of NaOH is prepared by dissolving 25 g of NaOH in 1 L of water. Calculate the number of moles of NaOH dissolved.
A. 0.05 mol
B. 0.1 mol
C. 0.15 mol
D. 0.2 mol
Question 13
A 2.00 L flask contains 0.500 mol of an ideal gas at a temperature of 298 K. If the gas is compressed to 1.00 L, what is the new pressure of the gas?
A. 2.00 atm
B. 3.00 atm
C. 4.00 atm
D. 5.00 atm
Question 14
A 0.5 M solution of K2Cr2O7 is electrolyzed u\sing a platinum electrode. What is the mass of Cr2O3 produced after 2 hours of electrolysis?
A. 10 g
B. 20 g
C. 30 g
D. 40 g
Question 15
The reaction of sodium hydroxide with hydrochloric acid is represented by the equation: NaOH + HCl → NaCl + H2O. If 25.0 mL of 0.100 M NaOH is added to 25.0 mL of 0.100 M HCl, what is the concentration of the resulting solution?
A. 0.0500 M
B. 0.100 M
C. 0.200 M
D. 0.500 M

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