POST UTME LASU 2020 Chemistry | Objective

Are you preparing for POST UTME LASU exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2020 Chemistry (Objective) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1
Determine the number of moles of $\text{H}_2$ produced when 2.5 moles of $\text{Ca}($s$)$ react with excess $\text{HCl}($aq$)$ according to the equation $\text{Ca}($s$) + 2\text{HCl}($aq$) \rightarrow \text{CaCl}_2($aq$) + \text{H}_2($g$)$.
Correct A. 1.25
B. 2.5
C. 3.75
D. 5.0

Correct Answer: A

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Question 2
A diagram of a titration setup is shown below. If 25.0 mL of 0.100 M $\text{NaOH}($aq$)$ is required to neutralize 25.0 mL of an acidic solution, what is the concentration of the acidic solution?
A. 0.0500 M
Correct B. 0.100 M
C. 0.200 M
D. 0.500 M

Correct Answer: B

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Question 3
The diagram below shows a simple black and white chemistry apparatus setup for a distillation process. If the boiling point of the liquid being distilled is 100°C, what is the temperature of the condenser?
Correct A. 90°C
B. 95°C
C. 99°C
D. 100°C

Correct Answer: A

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Question 4
A 2.50 L sample of a gas at 25.0°C and 1.00 atm is collected over water at 25.0°C. If the vapor pressure of water at 25.0°C is 23.8 torr, what is the partial pressure of the gas?
A. 0.975 atm
Correct B. 0.987 atm
C. 0.995 atm
D. 1.00 atm

Correct Answer: B

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Question 5
A 10.0 g sample of a compound containing only carbon and hydrogen is analyzed and found to contain 9.00 g of carbon and 1.00 g of hydrogen. What is the empirical formula of the compound?
A. CH
Correct B. C2H2
C. C3H4
D. C4H6

Correct Answer: B

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Question 6
The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of CO(g) and O2(g) from the following equation: CO2(g) → CO(g) + 1/2O2(g).
Correct A. -110.5 kJ/mol
B. -110.5 kJ/mol
C. -110.5 kJ/mol
D. -110.5 kJ/mol

Correct Answer: A

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Question 7
A 2.5 M solution of HCl is electrolyzed u\sing a platinum electrode. Calculate the mass of Cl2 gas produced at the anode after 2 hours, given that the current is 0.5 A and the cell potential is 2.0 V.
Correct A. 0.25 g
B. 0.25 g
C. 0.25 g
D. 0.25 g

Correct Answer: A

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Question 8
A sample of N2 gas at 25°C and 1 atm is compressed to 5 atm. Calculate the new volume of the gas, given that the temperature remains cons\tant.
Correct A. 0.2 L
B. 0.2 L
C. 0.2 L
D. 0.2 L

Correct Answer: A

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Question 9
A 1.0 M solution of H2SO4 is titrated with 1.0 M NaOH. Calculate the number of moles of H2SO4 required to react with 50 mL of NaOH.
Correct A. 0.05 mol
B. 0.05 mol
C. 0.05 mol
D. 0.05 mol

Correct Answer: A

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Question 10
A 2.0 M solution of NaCl is electrolyzed u\sing a platinum electrode. Calculate the mass of Cl2 gas produced at the anode after 1 hour, given that the current is 0.5 A and the cell potential is 2.0 V.
Correct A. 0.25 g
B. 0.25 g
C. 0.25 g
D. 0.25 g

Correct Answer: A

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Question 11
Determine the pH of a 0.1 M solution of HCl at 25°C. 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 12
A 25 mL sample of 0.5 M H2SO4 is titrated with 0.5 M NaOH. What is the pH of the solution after 15 mL of NaOH has been added?
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 13
A 100 mL sample of 0.2 M CH3COOH is titrated with 0.2 M NaOH. What is the pH of the solution after 20 mL of NaOH has been added?
A. 1
B. 2
Correct C. 3
D. 4

Correct Answer: C

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Question 14
A 50 mL sample of 0.1 M HCl is titrated with 0.1 M NaOH. What is the pH of the solution after 10 mL of NaOH has been added?
A. 1
B. 2
C. 3
Correct D. 4

Correct Answer: D

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Question 15
A 200 mL sample of 0.05 M H2SO4 is titrated with 0.05 M NaOH. What is the pH of the solution after 20 mL of NaOH has been added?
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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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. -1793.5 kJ/mol
B. -1793.5 kJ/mol
C. -1793.5 kJ/mol
Correct D. -1793.5 kJ/mol

Correct Answer: D

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Question 17
A 2.5 M solution of HCl is titrated with 0.5 M NaOH. Calculate the pH of the solution after 25 mL of NaOH has been added.
A. 2.5
B. 2.5
C. 2.5
Correct D. 2.5

Correct Answer: D

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Question 18
A 1.0 M solution of NH3 is mixed with 1.0 M HCl. Calculate the pH of the solution.
A. 9.25
B. 9.25
C. 9.25
Correct D. 9.25

Correct Answer: D

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Question 19
A 2.0 M solution of NaOH is titrated with 1.0 M HCl. Calculate the pH of the solution after 20 mL of HCl has been added.
A. 2.0
B. 2.0
C. 2.0
Correct D. 2.0

Correct Answer: D

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Question 20
A 1.5 M solution of H2SO4 is mixed with 1.5 M NaOH. Calculate the pH of the solution.
A. 0.5
B. 0.5
C. 0.5
Correct D. 0.5

Correct Answer: D

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Question 21
A 2.0 M solution of HCl is titrated with 1.0 M NaOH. Calculate the pH of the solution after 30 mL of NaOH has been added.
A. 2.0
B. 2.0
C. 2.0
Correct D. 2.0

Correct Answer: D

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Question 22
A 1.5 M solution of NH3 is mixed with 1.5 M HCl. Calculate the pH of the solution.
A. 9.25
B. 9.25
C. 9.25
Correct D. 9.25

Correct Answer: D

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Question 23
A 2.0 M solution of NaOH is titrated with 1.0 M HCl. Calculate the pH of the solution after 25 mL of HCl has been added.
A. 2.0
B. 2.0
C. 2.0
Correct D. 2.0

Correct Answer: D

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Question 24
A 1.5 M solution of H2SO4 is mixed with 1.5 M NaOH. Calculate the pH of the solution.
A. 0.5
B. 0.5
C. 0.5
Correct D. 0.5

Correct Answer: D

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Question 25
A 2.0 M solution of HCl is titrated with 1.0 M NaOH. Calculate the pH of the solution after 35 mL of NaOH has been added.
A. 2.0
B. 2.0
C. 2.0
D. 2.0

Correct Answer: VIEW ANSWER

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