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POST UTME ESUT 2019 Chemistry | Objective

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Question 1

Determine the number of moles of oxygen gas (O2) produced when 2.5 moles of hydrogen gas (H2) react with excess oxygen according to the equation: 2H2 + O2 → 2H2O. The reaction occurs at 25°C and 1 atm.

A. 1.25 moles

B. 2.5 moles

Correct C. 3.75 moles

D. 5 moles

Correct Answer: C

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Question 2

Identify the major product formed when 1-bromopropane reacts with sodium hydroxide (NaOH) in a reaction that involves an SN2 mechanism.

Correct A. 2-propanol

B. 1-propanol

C. 2-bromopropane

D. 1-bromopropane

Correct Answer: A

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Question 3

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 M

Correct B. 0.100 M

C. 0.200 M

D. 0.500 M

Correct Answer: B

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Question 4

A diagram of a circuit is shown below. If the battery is replaced with a 9.0 V battery, what will be the new reading on the ammeter?

A. 2.0 A

B. 3.0 A

Correct C. 4.0 A

D. 5.0 A

Correct Answer: C

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Question 5

A diagram of a plant cell is shown below. Identify the organelle responsible for protein synthesis.

A. mitochondria

B. nucleus

Correct C. ribosomes

D. lysosomes

Correct Answer: C

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Question 6

Determine the rate cons\tant (k) for the reaction: 2NO(g) + O2(g) → 2NO2(g), given that the initial concentrations of NO and O2 are 0.1 M and 0.2 M, respectively, and the rate of reaction is 0.05 M/s after 10 minutes.

A. \( k = 0.05 , \text{M/s} \)

Correct B. \( k = 0.1 , \text{M/s} \)

C. \( k = 0.2 , \text{M/s} \)

D. \( k = 0.3 , \text{M/s} \)

Correct Answer: B

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Question 7

A 2.5 L flask contains 0.5 mol of an ideal gas at 298 K. Calculate the work done (w) when the gas expands isothermally to a final volume of 5.0 L.

Correct A. \( w = - 1.5 , \text{kJ} \)

B. \( w = - 3.0 , \text{kJ} \)

C. \( w = - 4.5 , \text{kJ} \)

D. \( w = - 6.0 , \text{kJ} \)

Correct Answer: A

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Question 8

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of combustion of 1.0 mol of C6H12O6(s) at 298 K.

A. \( Delta H = - 2800 , \text{kJ} \)

Correct B. \( Delta H = - 3000 , \text{kJ} \)

C. \( Delta H = - 3200 , \text{kJ} \)

D. \( Delta H = - 3400 , \text{kJ} \)

Correct Answer: B

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Question 9

A 1.0 M solution of NaOH is mixed with a 1.0 M solution of HCl. Calculate the pH of the resulting solution.

Correct A. \( \text{pH} = 7 \)

B. \( \text{pH} = 8 \)

C. \( \text{pH} = 9 \)

D. \( \text{pH} = 10 \)

Correct Answer: A

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Question 10

A 2.0 L flask contains 0.5 mol of an ideal gas at 298 K. Calculate the entropy change (ΔS) when the gas expands isothermally to a final volume of 5.0 L.

A. \( Delta S = 1.5 , \text{J/K} \)

Correct B. \( Delta S = 3.0 , \text{J/K} \)

C. \( Delta S = 4.5 , \text{J/K} \)

D. \( Delta S = 6.0 , \text{J/K} \)

Correct Answer: B

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Question 11

Determine the oxidation state of the metal in the compound [Co(H2O)6]SO4.

Correct A. +2

B. +3

C. +4

D. +5

Correct Answer: A

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Question 12

A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the pH of the solution after the addition of 15.0 mL of NaOH.

A. 2.00

Correct B. 2.50

C. 3.00

D. 3.50

Correct Answer: B

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Question 13

The diagram below shows a cell with a salt bridge.

A. The cell is a galvanic cell.

B. The cell is an electrolytic cell.

Correct C. The salt bridge is used to connect the two half-cells.

D. The salt bridge is used to separate the two half-cells.

Correct Answer: C

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Question 14

A 2.00 g sample of an unknown hydrocarbon is burned in a combustion calorimeter. The heat of combustion is 12.5 kJ/g. Calculate the molar mass of the hydrocarbon.

A. 50.0 g/mol

B. 75.0 g/mol

C. 100 g/mol

Correct D. 125 g/mol

Correct Answer: D

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Question 15

The diagram below shows a titration setup.

A. The burette contains the titrant.

Correct B. The beaker contains the analyte.

C. The burette contains the analyte.

D. The beaker contains the titrant.

Correct Answer: B

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Question 16

A sample of an ideal gas at 25°C and 1 atm is heated to 50°C at cons\tant pressure. Calculate the ratio of the final volume to the initial volume.

Correct A. 1.25

B. 2.00

C. 2.50

D. 3.00

Correct Answer: A

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Question 17

A 2.5 g sample of a metal carbonate is heated to produce a metal oxide and carbon dioxide gas. If the mass of the metal oxide produced is 1.8 g, calculate the molar mass of the metal.

A. 40.0 g/mol

Correct B. 50.0 g/mol

C. 60.0 g/mol

D. 70.0 g/mol

Correct Answer: B

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Question 18

A solution containing 5.0 g of NaCl is prepared by dissolving the salt in 100 mL of water. Calculate the molarity of the solution.

A. 0.10 M

Correct B. 0.20 M

C. 0.30 M

D. 0.40 M

Correct Answer: B

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Question 19

A 2.5 L sample of a gas at 25°C and 1 atm is compressed to 1 L at cons\tant temperature. Calculate the final pressure of the gas.

A. 4.0 atm

B. 5.0 atm

Correct C. 6.0 atm

D. 7.0 atm

Correct Answer: C

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Question 20

A 1.0 g sample of a metal is heated in a crucible to produce a metal oxide. If the mass of the metal oxide produced is 1.5 g, calculate the percentage yield of the reaction.

A. 50%

B. 60%

Correct C. 70%

D. 80%

Correct Answer: C

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Question 21

A 2.50-g sample of a metal oxide is heated in a crucible until it decomposes completely. The mass of the metal obtained is 1.25 g. Calculate the percentage yield of the metal if the theoretical yield is 1.50 g.

Correct A. 75%

B. 80%

C. 85%

D. 90%

Correct Answer: A

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Question 22

A gas at 27°C and 1 atm is compressed to 4 atm. If the initial volume is 2.5 L, what is the final volume of the gas?

A. 1.25 L

B. 2.5 L

Correct C. 5.0 L

D. 10.0 L

Correct Answer: C

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Question 23

A solution containing 0.50 M NaOH is mixed with a solution containing 0.25 M HCl. What is the concentration of the resulting solution?

A. 0.25 M

B. 0.50 M

Correct C. 0.75 M

D. 1.00 M

Correct Answer: C

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Question 24

A 10.0-g sample of a metal is heated in a crucible until it decomposes completely. The mass of the metal obtained is 5.0 g. Calculate the percentage yield of the metal if the theoretical yield is 6.0 g.

A. 83%

Correct B. 85%

C. 87%

D. 90%

Correct Answer: B

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Question 25

A gas at 37°C and 2 atm is expanded to 1 atm. If the initial volume is 3.0 L, what is the final volume of the gas?

A. 1.5 L

B. 3.0 L

Correct C. 4.5 L

D. 6.0 L

Correct Answer: C

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