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POST UTME UNILAG 2022 Chemistry | Objective

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Question 1

Determine the molar mass of a gas that occupies 2.5 L at 273 K and 1 atm. Use the ideal gas law to calculate the number of moles.

Correct A. \( 0.0224 , \text{mol} \)

B. \( 0.0448 , \text{mol} \)

C. \( 0.0672 , \text{mol} \)

D. \( 0.0896 , \text{mol} \)

Correct Answer: A

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Question 2

A metal M reacts with chlorine gas to form a white solid. The reaction is as follows: M + Cl2 → MCl2. If 2.5 g of M reacts with 5.0 g of Cl2, what is the percentage yield of MCl2 if the molar mass of M is 55.85 g/mol and the molar mass of Cl2 is 70.90 g/mol?

A. ( 85% )

Correct B. ( 90% )

C. ( 95% )

D. ( 98% )

Correct Answer: B

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Question 3

A 2.0 M solution of HCl is mixed with a 2.0 M solution of NaOH. If 50.0 mL of each solution is used, what is the pH of the resulting solution?

A. ( 1.0 )

Correct B. ( 2.0 )

C. ( 3.0 )

D. ( 4.0 )

Correct Answer: B

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Question 4

A diagram of a titration setup is shown below. If 25.0 mL of 0.100 M NaOH is required to reach the equivalence point, what is the concentration of the HCl solution?

A. \( 0.0500 , \text{M} \)

Correct B. \( 0.100 , \text{M} \)

C. \( 0.200 , \text{M} \)

D. \( 0.500 , \text{M} \)

Correct Answer: B

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Question 5

A diagram of a distillation setup is shown below. If the temperature of the distillate is 95°C and the boiling point of the solvent is 100°C, what is the percentage recovery of the solvent?

A. ( 80% )

B. ( 85% )

Correct C. ( 90% )

D. ( 95% )

Correct Answer: C

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Question 6

At 273.15 K, 1 mole of an ideal gas occupies a volume of 22.4 L. If the temperature is increased to 373.15 K, what is the new volume of the gas, assuming it remains ideal?

Correct A. 11.2 L

B. 22.4 L

C. 44.8 L

D. 67.2 L

Correct Answer: A

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Question 7

A metal alloy contains 80% copper and 20% zinc by mass. If a 250 g sample of the alloy is dissolved in acid, what is the mass of copper that will be dissolved?

A. 100 g

Correct B. 150 g

C. 200 g

D. 250 g

Correct Answer: B

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Question 8

The element with atomic number 12 is _______.

A. Mg

Correct B. Ca

C. K

D. Na

Correct Answer: B

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Question 9

A solution contains 2.5 g of NaCl in 100 mL of water. What is the molarity of the solution?

A. 0.1 M

B. 0.2 M

Correct C. 0.3 M

D. 0.4 M

Correct Answer: C

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Question 10

The diagram below shows a titration setup. If 25 mL of 0.1 M NaOH is added to the burette, what is the pH of the solution?

A. 7

B. 8

Correct C. 9

D. 10

Correct Answer: C

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Question 11

The rate cons\tant (k) of a first-order reaction is related to the half-life \( t_\( 1/2 \ \)) by the equation: k = ln(2) / t_\( 1/2 \). If the half-life of a reaction is 10 minutes, what is the rate cons\tant (k) in min^\( -1 \)?

Correct A. 0.0693 min^\( -1 \)

B. 0.693 min^\( -1 \)

C. 6.93 min^\( -1 \)

D. 69.3 min^\( -1 \)

Correct Answer: A

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Question 12

A solution contains 0.1 M NaCl. If 10 mL of this solution is diluted to 100 mL, what is the concentration of the resulting solution?

Correct A. 0.01 M

B. 0.1 M

C. 1 M

D. 10 M

Correct Answer: A

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Question 13

The reaction: 2NO(g) + O_(2)(g) → 2NO_(2)(g) has a rate cons\tant (k) of 0.05 min^\( -1 \) at 25°C. If the initial concentrations of NO and O_(2) are 0.1 M and 0.2 M, respectively, what is the rate of reaction (r) in M min^\( -1 \)?

Correct A. 0.0002 M min^\( -1 \)

B. 0.002 M min^\( -1 \)

C. 0.02 M min^\( -1 \)

D. 0.2 M min^\( -1 \)

Correct Answer: A

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Question 14

A 0.1 M solution of NaOH is titrated with 0.1 M HCl. If 20 mL of HCl is required to reach the equivalence point, what is the volume of NaOH required to reach the equivalence point?

A. 10 mL

Correct B. 20 mL

C. 30 mL

D. 40 mL

Correct Answer: B

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Question 15

The solubility of a sparingly soluble salt, M_(2)X, in water is 0.01 g/100 mL. If 100 mL of a 0.1 M solution of MCl is added to 100 mL of water, what is the concentration of MCl in the resulting solution?

Correct A. 0.01 M

B. 0.1 M

C. 1 M

D. 10 M

Correct Answer: A

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Question 16

Determine the pH of a 0.1 M solution of HCl after 10 mL of 0.1 M NaOH has been added to 20 mL of the HCl solution. The initial pH of the HCl solution is 1.0.

A. 1.5

Correct B. 2.5

C. 3.5

D. 4.5

Correct Answer: B

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Question 17

A 25 mL sample of a 0.2 M solution of CaCl2 is mixed with 25 mL of a 0.2 M solution of Na2CO3. Determine the concentration of CaCO3 formed in the resulting solution.

A. 0.02 M

B. 0.04 M

Correct C. 0.06 M

D. 0.08 M

Correct Answer: C

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Question 18

A metal (X) reacts with HCl to produce a gas (Y) and a salt (Z). The reaction is as follows: X + 2HCl → Y + Z. If 2.5 g of X reacts with 10 mL of 0.5 M HCl, determine the molar mass of X.

A. 50 g/mol

Correct B. 75 g/mol

C. 100 g/mol

D. 125 g/mol

Correct Answer: B

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Question 19

A solution of NaOH is added to a solution of HCl in a titration experiment. The initial pH of the HCl solution is 1.0. If 20 mL of 0.1 M NaOH is added to 20 mL of the HCl solution, determine the pH of the resulting solution.

A. 2.0

B. 2.5

Correct C. 3.0

D. 3.5

Correct Answer: C

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Question 20

A 25 mL sample of a 0.2 M solution of CuSO4 is mixed with 25 mL of a 0.2 M solution of NaOH. Determine the concentration of Cu(OH)2 formed in the resulting solution.

A. 0.02 M

Correct B. 0.04 M

C. 0.06 M

D. 0.08 M

Correct Answer: B

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Question 21

Determine the pH of a 0.1 M solution of HCl.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 22

The diagram below shows a titration setup. What is the purpose of the burette?

Correct A. To measure the volume of the acid

B. To measure the volume of the base

C. To mix the acid and base

D. To measure the pH of the solution

Correct Answer: A

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Question 23

Calculate the molarity of a solution containing 25 g of NaCl in 250 mL of water.

A. 0.1 M

Correct B. 0.2 M

C. 0.3 M

D. 0.4 M

Correct Answer: B

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Question 24

The diagram below shows a periodic table. Identify the group number of the element with atomic number 12.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 25

The pH of a solution is 4. What is the concentration of H+ ions in the solution?

Correct A. 10^-4 M

B. 10^-3 M

C. 10^-2 M

D. 10^-1 M

Correct Answer: A

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