POST UTME UNIOSUN 2019 Chemistry | Objective

Are you preparing for POST UTME UNIOSUN exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2019 Chemistry (Objective) questions designed to simulate the real exam environment.

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Question 1
The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of combustion of 2.5 g of carbon at 298 K.
Correct A. -981.25 kJ
B. -981.375 kJ
C. -981.5 kJ
D. -981.625 kJ

Correct Answer: A

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Question 2
A 0.500 M solution of NaOH is mixed with a 0.500 M solution of HCl. What is the pH of the resulting solution?
A. 1.00
Correct B. 2.00
C. 3.00
D. 4.00

Correct Answer: B

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Question 3
The half-life of a radioactive subs\tance is 5.0 days. If 100 g of the subs\tance initially exists, how much will remain after 20 days?
A. 12.5 g
Correct B. 25.0 g
C. 37.5 g
D. 50.0 g

Correct Answer: B

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Question 4
A gas at 300 K and 1 atm expands to 2 atm against a cons\tant external pressure of 1 atm. What is the work done by the gas?
Correct A. 2.303 kJ
B. 3.303 kJ
C. 4.303 kJ
D. 5.303 kJ

Correct Answer: A

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Question 5
The s\tandard Gibbs free energy change for the reaction 2H2(g) + O2(g) → 2H2O(l) is -237 kJ/mol. What is the equilibrium cons\tant for this reaction?
Correct A. 1.00 × 10^12
B. 1.00 × 10^15
C. 1.00 × 10^18
D. 1.00 × 10^21

Correct Answer: A

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Question 6
A 0.1 M solution of AgNO3 is mixed with a 0.1 M solution of NaCl. If the resulting solution is a double salt, what is the molar concentration of the double salt?
Correct A. 0.05 M
B. 0.1 M
C. 0.2 M
D. 0.05 M

Correct Answer: A

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Question 7
A metal M has an electron configuration of [Ar] 3d^5 4s^2. Which of the following is a possible oxidation state for M?
A. +2
Correct B. +3
C. +4
D. +5

Correct Answer: B

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Question 8
A solution of H2O2 is treated with a strong acid. What is the resulting product?
Correct A. H2O
B. H2SO4
C. HCl
D. HNO3

Correct Answer: A

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Question 9
A 1.0 M solution of NaOH is mixed with a 1.0 M solution of HCl. What is the resulting pH?
Correct A. 7
B. 10
C. 12
D. 14

Correct Answer: A

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Question 10
A metal M has a s\tandard reduction potential of +0.5 V. What is the s\tandard reduction potential of the metal ion M2+?
Correct A. -0.5 V
B. +0.5 V
C. +1.0 V
D. -1.0 V

Correct Answer: A

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Question 11
A 0.1 M solution of a weak acid HA is titrated with 0.1 M NaOH. If 20 mL of NaOH is required to reach the equivalence point, calculate the number of moles of HA present in 100 mL of the acid solution.
A. 0.0025 mol
Correct B. 0.005 mol
C. 0.0075 mol
D. 0.01 mol

Correct Answer: B

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Question 12
The diagram below shows a titration setup. If the burette contains 0.1 M NaOH and the initial volume is 20 mL, what is the concentration of the acid solution if 25 mL of NaOH is required to reach the equivalence point?
A. 0.05 M
B. 0.1 M
Correct C. 0.15 M
D. 0.2 M

Correct Answer: C

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Question 13
A polymer has a molecular weight of 5000 g/mol and a degree of polymerization of 100. What is the molar mass of the repeating unit?
A. 50 g/mol
B. 100 g/mol
Correct C. 500 g/mol
D. 1000 g/mol

Correct Answer: C

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Question 14
The diagram below shows a chemical apparatus setup. Identify the part labeled A.
Correct A. Burette
B. Beaker
C. Conical flask
D. Test tube

Correct Answer: A

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Question 15
A 1.0 M solution of a strong acid HA is titrated with 1.0 M NaOH. If 20 mL of NaOH is required to reach the equivalence point, calculate the number of moles of HA present in 100 mL of the acid solution.
A. 0.0025 mol
Correct B. 0.005 mol
C. 0.0075 mol
D. 0.01 mol

Correct Answer: B

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Question 16
The diagram below shows a titration setup. If the burette contains 1.0 M NaOH and the initial volume is 20 mL, what is the concentration of the acid solution if 25 mL of NaOH is required to reach the equivalence point?
A. 0.05 M
B. 0.1 M
Correct C. 0.15 M
D. 0.2 M

Correct Answer: C

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Question 17
A polymer has a molecular weight of 10000 g/mol and a degree of polymerization of 200. What is the molar mass of the repeating unit?
A. 50 g/mol
B. 100 g/mol
Correct C. 500 g/mol
D. 1000 g/mol

Correct Answer: C

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Question 18
The pH of a solution is 4.5. What is the concentration of hydrogen ions in moles per liter?
Correct A. 1.0 x 10^-5 M
B. 1.0 x 10^-4 M
C. 1.0 x 10^-3 M
D. 1.0 x 10^-2 M

Correct Answer: A

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Question 19
A sample of gas occupies 2.5 liters at a pressure of 1.2 atm. What is the volume of the gas at a pressure of 3.0 atm, assuming the temperature remains cons\tant?
A. 1.0 L
Correct B. 1.5 L
C. 2.0 L
D. 2.5 L

Correct Answer: B

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Question 20
A solution contains 25.0 g of NaCl. What is the molarity of the solution, assuming a density of 1.0 g/mL?
A. 0.5 M
Correct B. 1.0 M
C. 1.5 M
D. 2.0 M

Correct Answer: B

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Question 21
A metal reacts with oxygen to form a compound with the formula M2O3. If 25.0 g of the metal is used, what is the mass of oxygen in the compound?
A. 10.0 g
B. 15.0 g
Correct C. 20.0 g
D. 25.0 g

Correct Answer: C

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Question 22
A solution contains 50.0 mL of 0.5 M HCl. What is the concentration of the solution after adding 25.0 mL of 1.0 M NaOH?
A. 0.25 M
B. 0.5 M
Correct C. 0.75 M
D. 1.0 M

Correct Answer: C

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Question 23
A metal has an atomic radius of 200 pm. What is the expected atomic radius of the metal's ion, assuming it loses 2 electrons?
A. 150 pm
Correct B. 175 pm
C. 200 pm
D. 225 pm

Correct Answer: B

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Question 24
A solution contains 10.0 g of glu\cose. What is the molarity of the solution, assuming a density of 1.0 g/mL?
A. 0.1 M
Correct B. 0.5 M
C. 1.0 M
D. 2.0 M

Correct Answer: B

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Question 25
A metal reacts with oxygen to form a compound with the formula MO2. If 25.0 g of the metal is used, what is the mass of oxygen in the compound?
A. 10.0 g
B. 15.0 g
Correct C. 20.0 g
D. 25.0 g

Correct Answer: C

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