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POST UTME LASU 2022 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 2022 Chemistry (Objective) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1

Determine the oxidation state of the underlined atom in the compound [Cr(H2O)6]Cl3.

Correct A. +3

B. +2

C. +6

D. +1

Correct Answer: A

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Question 2

A 2.5 L flask contains 0.5 mol of an ideal gas at 27°C. Calculate the pressure of the gas u\sing the ideal gas law.

A. 1.5 atm

B. 2.0 atm

Correct C. 2.5 atm

D. 3.0 atm

Correct Answer: C

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Question 3

The diagram below shows a titration setup. Identify the part labeled A.

Correct A. Burette

B. Conical Flask

C. Pipette

D. Thermometer

Correct Answer: A

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Question 4

Solve the equation \( \log_{10} \( x^2 \ \) = 4 ) for x.

A. 2

B. 4

Correct C. 10

D. 20

Correct Answer: C

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Question 5

A 25 mL sample of a solution containing 0.1 M NaOH is titrated with 0.1 M HCl. Calculate the number of moles of HCl required to reach the equivalence point.

A. 0.0025 mol

Correct B. 0.0050 mol

C. 0.0075 mol

D. 0.0100 mol

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 3.5, what is the pH of the solution after the addition of 20 mL of 0.1 M NaOH?

A. 4.5

B. 5.5

Correct C. 6.5

D. 7.5

Correct Answer: C

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Question 7

A metal M reacts with chlorine gas to form a white solid MX. If the molar mass of M is 55 g/mol and the molar mass of MX is 120 g/mol, what is the molar mass of X?

A. 65 g/mol

Correct B. 75 g/mol

C. 85 g/mol

D. 95 g/mol

Correct Answer: B

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Question 8

A 1.0 M solution of a non-electrolyte solute is prepared by dissolving 18 g of the solute in 1.0 L of water. What is the molar mass of the solute?

Correct A. 18 g/mol

B. 20 g/mol

C. 22 g/mol

D. 24 g/mol

Correct Answer: A

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Question 9

A 2.0 M solution of a weak base B is prepared by dissolving 20 g of B in 1.0 L of water. If the initial pH of the base solution is 10.5, what is the pH of the solution after the addition of 10 mL of 1.0 M HCl?

A. 9.5

B. 10.5

Correct C. 11.5

D. 12.5

Correct Answer: C

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Question 10

A metal M reacts with oxygen gas to form a white solid MO. If the molar mass of M is 40 g/mol and the molar mass of MO is 80 g/mol, what is the molar mass of O?

A. 40 g/mol

Correct B. 60 g/mol

C. 80 g/mol

D. 100 g/mol

Correct Answer: B

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Question 11

Determine the number of moles of oxygen gas (O2) required to react with 2.5 moles of carbon monoxide (CO) in the following equation: 2CO + O2 → 2CO2.

Correct A. 1.25 moles

B. 2.5 moles

C. 5 moles

D. 10 moles

Correct Answer: A

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Question 12

A sample of nitrogen gas (N2) occupies a volume of 2.5 liters at a pressure of 1 atm and a temperature of 298 K. Calculate the number of moles of N2 gas present in the sample.

A. 0.1 moles

Correct B. 0.2 moles

C. 0.5 moles

D. 1 mole

Correct Answer: B

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Question 13

The atomic radius of a certain element is 100 pm. If the element has an atomic number of 12, what is its electron configuration?

A. 1s² 2s² 2p⁶ 3s²

B. 1s² 2s² 2p⁶ 3s² 3p⁶

Correct C. 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

D. 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4p⁶

Correct Answer: C

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Question 14

A solution contains 2.5 grams of sodium chloride (NaCl) dissolved in 100 mL of water. Calculate the molarity of the solution.

A. 0.1 M

B. 0.2 M

Correct C. 0.5 M

D. 1 M

Correct Answer: C

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Question 15

A catalyst is added to a reaction mixture containing 2.5 moles of hydrogen gas (H2) and 2.5 moles of oxygen gas (O2). The reaction is: 2H2 + O2 → 2H2O. Calculate the number of moles of water (H2O) produced after 10 minutes.

A. 2.5 moles

Correct B. 5 moles

C. 10 moles

D. 20 moles

Correct Answer: B

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Question 16

Determine the pH of a solution containing 0.1 M HCl and 0.1 M NaOH after 10 mL of 1 M HCl is added to 100 mL of the solution.

A. 2

B. 3

C. 4

Correct D. 5

Correct Answer: D

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Question 17

A sample of nitrogen gas is collected over water at a temperature of 25°C and a pressure of 1 atm. Calculate the partial pressure of nitrogen gas in the sample.

A. 0.95 atm

B. 0.99 atm

Correct C. 1.00 atm

D. 1.05 atm

Correct Answer: C

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Question 18

A 2.5 g sample of a polymer is dissolved in 100 mL of a solvent. The solution has a vis\cosity of 1.2 Pa·s. Calculate the molar mass of the polymer.

A. 10^5 g/mol

Correct B. 10^6 g/mol

C. 10^7 g/mol

D. 10^8 g/mol

Correct Answer: B

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Question 19

A 50 mL sample of a solution containing 0.1 M HCl is titrated with 1 M NaOH. Calculate the volume of NaOH required to reach the equivalence point.

A. 25 mL

Correct B. 50 mL

C. 75 mL

D. 100 mL

Correct Answer: B

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Question 20

A sample of a metal oxide is heated in a furnace at 1000°C. The resulting gas has a volume of 2.5 L at 1 atm. Calculate the molar mass of the metal oxide.

A. 100 g/mol

B. 200 g/mol

Correct C. 300 g/mol

D. 400 g/mol

Correct Answer: C

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Question 21

The reaction of sodium hydroxide with hydrochloric acid is a classic example of a double displacement reaction. What is the net ionic equation for this reaction?

A. 2NaOH(aq) + 2HCl(aq) → 2NaCl(aq) + 2H2O(l)

B. NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Correct C. 2NaOH(aq) + 2HCl(aq) → 2NaCl(aq) + 2H2O(l)

D. NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Correct Answer: C

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Question 22

A 0.1 M solution of sodium hydroxide is mixed with a 0.1 M solution of hydrochloric acid. 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 23

The diagram below shows a titration setup.

Correct A. The burette contains the acid.

B. The beaker contains the acid.

C. The burette contains the base.

D. The beaker contains the base.

Correct Answer: A

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Question 24

The reaction of sodium hydroxide with hydrochloric acid is a classic example of a double displacement reaction. What is the net ionic equation for this reaction?

A. 2NaOH(aq) + 2HCl(aq) → 2NaCl(aq) + 2H2O(l)

B. NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Correct C. 2NaOH(aq) + 2HCl(aq) → 2NaCl(aq) + 2H2O(l)

D. NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Correct Answer: C

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Question 25

A 0.1 M solution of sodium hydroxide is mixed with a 0.1 M solution of hydrochloric acid. What is the pH of the resulting solution?

Correct A. 7

B. 8

C. 9

D. 10

Correct Answer: A

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