POST UTME UNILORIN 2019 Chemistry | Objective

Are you preparing for POST UTME UNILORIN 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
A 2.5g sample of a metal carbonate is heated to a cons\tant mass. If 0.75g of the metal oxide is obtained, calculate the percentage yield of the metal oxide.
A. 50%
Correct B. 60%
C. 70%
D. 80%

Correct Answer: B

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Question 2
A diagram of a titration apparatus is shown below. If 25.0mL of 0.1M HCl is required to reach the equivalence point, calculate the number of moles of NaOH used.
A. 0.0025mol
Correct B. 0.0050mol
C. 0.0075mol
D. 0.010mol

Correct Answer: B

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Question 3
A 2.0g sample of a metal hydroxide is dissolved in 100mL of water to give a solution with a pH of 10.5. Calculate the concentration of the metal hydroxide.
A. 0.1M
B. 0.2M
Correct C. 0.3M
D. 0.4M

Correct Answer: C

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Question 4
A diagram of a gas apparatus is shown below. If the pressure of the gas is 2.0atm and the volume is 10.0L, calculate the number of moles of gas present.
A. 0.2mol
B. 0.4mol
Correct C. 0.6mol
D. 0.8mol

Correct Answer: C

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Question 5
A 1.0g sample of a metal is heated to a cons\tant mass. If 0.5g of the metal oxide is obtained, calculate the percentage yield of the metal oxide.
A. 50%
Correct B. 60%
C. 70%
D. 80%

Correct Answer: B

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Question 6
A 0.1 M solution of a weak acid HA is titrated with 0.1 M NaOH. If the initial pH of the acid solution is 4.5, what is the pH after the addition of 20 mL of 0.1 M NaOH?
A. 4.5
Correct B. 5.5
C. 6.5
D. 7.5

Correct Answer: B

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Question 7
A metal M \( atomic mass 50 g/mol \) reacts with chlorine gas to form a compound MCl2. If 2.5 g of M is reacted with 10 mL of Cl2, what is the volume of Cl2 gas consumed?
A. 10 mL
Correct B. 20 mL
C. 30 mL
D. 40 mL

Correct Answer: B

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Question 8
A 1.0 M solution of a salt Na2SO4 is prepared by dissolving 58.44 g of Na2SO4 in 1 L of water. What is the molarity of the sulfate ion \( SO42- \) in the solution?
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 9
A 0.1 M solution of a weak base B is titrated with 0.1 M HCl. If the initial pH of the base solution is 10.5, what is the pH after the addition of 20 mL of 0.1 M HCl?
A. 5.5
B. 6.5
C. 7.5
Correct D. 8.5

Correct Answer: D

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Question 10
A metal M \( atomic mass 60 g/mol \) reacts with oxygen gas to form a compound MO2. If 3.0 g of M is reacted with 10 mL of O2, what is the volume of O2 gas consumed?
A. 10 mL
B. 20 mL
Correct C. 30 mL
D. 40 mL

Correct Answer: C

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Question 11
The reaction between potassium permanganate and hydrogen peroxide is a classic example of a redox reaction. What is the oxidation state of manganese in KMnO4?
Correct A. +7
B. +6
C. +5
D. +4

Correct Answer: A

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Question 12
A solution of 0.1 M NaOH is mixed with a solution of 0.1 M HCl. What is the pH of the resulting solution?
Correct A. 7
B. 8
C. 9
D. 10

Correct Answer: A

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Question 13
The half-life of a radioactive subs\tance is 5 years. If the initial amount of the subs\tance is 100 g, what is the amount remaining after 10 years?
A. 50 g
B. 25 g
C. 12.5 g
Correct D. 6.25 g

Correct Answer: D

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Question 14
A diagram of a titration setup is shown below. What is the purpose of the burette in this setup?
Correct A. To measure the volume of the solution
B. To measure the pH of the solution
C. To mix the solutions
D. To filter the solution

Correct Answer: A

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Question 15
The reaction between sodium hydroxide and acetic acid is a classic example of a neutralization reaction. What is the products of this reaction?
Correct A. Sodium acetate and water
B. Sodium hydroxide and acetic acid
C. Acetic acid and water
D. Sodium hydroxide and sodium acetate

Correct Answer: A

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Question 16
The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of CaCO3(s) u\sing the following reaction: CaO(s) + CO2(g) → CaCO3(s).
A. -1206.5 kJ/mol
B. -1206.5 kJ/mol
C. -1206.5 kJ/mol
Correct D. -1206.5 kJ/mol

Correct Answer: D

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Question 17
The solubility of a sparingly soluble salt, AgCl, in water is 1.2 × 10^\( -5 \) mol/L at 25°C. Calculate the concentration of Ag+ ions in the saturated solution.
Correct A. 1.2 × 10^\( -5 \) M
B. 1.2 × 10^\( -5 \) M
C. 1.2 × 10^\( -5 \) M
D. 1.2 × 10^\( -5 \) M

Correct Answer: A

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Question 18
A 2.5 L flask contains 0.15 mol of CO2 at 25°C. Calculate the partial pressure of CO2 in the flask.
Correct A. 0.75 atm
B. 0.75 atm
C. 0.75 atm
D. 0.75 atm

Correct Answer: A

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Question 19
A 0.25 M solution of NaOH is mixed with a 0.25 M solution of HCl. Calculate the pH of the resulting solution.
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 20
A 2.5 L flask contains 0.15 mol of CO2 at 25°C. Calculate the number of moles of CO2 that will be present in the flask at 50°C.
Correct A. 0.15 mol
B. 0.15 mol
C. 0.15 mol
D. 0.15 mol

Correct Answer: A

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Question 21
Determine the pH of a 0.1 M solution of HCl at 25°C, given that the dissociation cons\tant of HCl is 10^\( -7 \).
A. 1
B. 2
C. 3
Correct D. 4

Correct Answer: D

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Question 22
A metal 'M' reacts with dilute HCl to produce a gas 'G'. The reaction is as follows: M + 2HCl → G + 2H2O. If 2.5 g of M reacts with 10 cm3 of 2 M HCl, calculate the volume of G produced at STP.
A. 10 cm3
Correct B. 20 cm3
C. 30 cm3
D. 40 cm3

Correct Answer: B

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Question 23
A solution containing 0.1 M HCl and 0.1 M NaOH is prepared. Calculate the pH of the solution after 10 minutes.
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 24
A metal 'M' reacts with oxygen to form a basic oxide. The reaction is as follows: 4M + 3O2 → 2M2O3. If 2.5 g of M reacts with 10 cm3 of O2 at STP, calculate the volume of O2 required.
A. 10 cm3
B. 20 cm3
Correct C. 30 cm3
D. 40 cm3

Correct Answer: C

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Question 25
A solution containing 0.1 M HCl and 0.1 M NaOH is prepared. Calculate the pH of the solution after 10 minutes.
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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