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POST UTME OAU 2024 Chemistry | Objective

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Question 1

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. 1.0

Correct B. 2.0

C. 3.0

D. 4.0

Correct Answer: B

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Question 2

A 25.0 g sample of a metal carbonate is heated to produce a metal oxide and carbon dioxide gas. The mass of the metal oxide produced is 15.0 g. Calculate the molar mass of the metal carbonate.

A. 100 g/mol

B. 150 g/mol

Correct C. 200 g/mol

D. 250 g/mol

Correct Answer: C

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Question 3

A 2.0 L sample of a gas at 25°C and 1.0 atm is collected over water at 25°C. The vapor pressure of water at 25°C is 23.8 mmHg. Calculate the partial pressure of the gas.

Correct A. 0.97 atm

B. 0.98 atm

C. 0.99 atm

D. 1.0 atm

Correct Answer: A

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Question 4

A 50.0 mL sample of a 0.1 M solution of FeCl3 is mixed with 50.0 mL of a 0.1 M solution of NaOH. What is the concentration of the resulting solution?

A. 0.05 M

Correct B. 0.10 M

C. 0.15 M

D. 0.20 M

Correct Answer: B

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Question 5

A 100.0 mL sample of a 0.1 M solution of H2SO4 is mixed with 100.0 mL of a 0.1 M solution of NaOH. What is the pH of the resulting solution?

A. 1.0

B. 2.0

C. 3.0

Correct D. 4.0

Correct Answer: D

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Question 6

The rate cons\tant (k) of a first-order reaction is given by the equation: k = Ae^\( -Ea/RT \). If the activation energy (Ea) is 100 kJ/mol, the gas cons\tant (R) is 8.314 J/mol*K, and the temperature (T) is 300 K, what is the value of the rate cons\tant (k) if the pre-exponential factor (A) is 1.0 x 10^10 s^-1?

A. 1.0 x 10^6 s^-1

B. 1.0 x 10^7 s^-1

Correct C. 1.0 x 10^8 s^-1

D. 1.0 x 10^9 s^-1

Correct Answer: C

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Question 7

A solution contains 0.1 M Fe^2+ ions. If 10 mL of 1 M NaOH is added to 90 mL of the solution, what is the concentration of Fe(OH)2 that forms?

A. 0.01 M

Correct B. 0.1 M

C. 0.5 M

D. 1 M

Correct Answer: B

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Question 8

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. If 1.0 mol of CO2 is formed at 298 K, what is the change in entropy (ΔS) for the reaction?

Correct A. -1.3 J/mol*K

B. -13 J/mol*K

C. -130 J/mol*K

D. -1.3 kJ/mol*K

Correct Answer: A

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Question 9

A solution contains 0.1 M Fe^3+ ions. If 10 mL of 1 M NaOH is added to 90 mL of the solution, what is the concentration of Fe(OH)3 that forms?

A. 0.01 M

Correct B. 0.1 M

C. 0.5 M

D. 1 M

Correct Answer: B

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Question 10

The s\tandard enthalpy of formation of H2O(l) is -285.8 kJ/mol. If 1.0 mol of H2O is formed at 298 K, what is the change in entropy (ΔS) for the reaction?

Correct A. -1.3 J/mol*K

B. -13 J/mol*K

C. -130 J/mol*K

D. -1.3 kJ/mol*K

Correct Answer: A

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Question 11

The reaction of zinc metal with copper(II) sulfate solution is represented by the equation: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s). If 25.0 mL of 0.100 M CuSO4(aq) is mixed with 25.0 mL of 0.100 M Zn(NO3)2(aq), what is the limiting reac\tant?

A. Zn(s)

Correct B. CuSO4(aq)

C. ZnSO4(aq)

D. Cu(s)

Correct Answer: B

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Question 12

A 2.50 g sample of a metal carbonate is heated to produce a 0.500 g sample of the metal oxide. What is the molar mass of the metal carbonate?

A. 50.0 g/mol

B. 75.0 g/mol

Correct C. 100 g/mol

D. 125 g/mol

Correct Answer: C

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Question 13

A solution of 0.100 M HCl(aq) is mixed with a solution of 0.100 M NaOH(aq) in a 1:1 ratio. What is the pH of the resulting solution?

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 14

A 25.0 mL sample of 0.100 M HCl(aq) is titrated with 0.100 M NaOH(aq). What is the volume of NaOH(aq) required to reach the equivalence point?

A. 25.0 mL

Correct B. 50.0 mL

C. 75.0 mL

D. 100 mL

Correct Answer: B

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Question 15

A 1.00 g sample of a metal is heated in a crucible to produce a 0.500 g sample of the metal oxide. What is the percentage yield of the metal oxide?

A. 50.0%

Correct B. 75.0%

C. 80.0%

D. 90.0%

Correct Answer: B

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Question 16

A 25.0 mL sample of 0.100 M HCl(aq) is titrated with 0.100 M NaOH(aq). What is the pH of the resulting solution at the equivalence point?

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 17

A 1.00 g sample of a metal is heated in a crucible to produce a 0.500 g sample of the metal oxide. What is the molar mass of the metal?

A. 50.0 g/mol

B. 75.0 g/mol

Correct C. 100 g/mol

D. 125 g/mol

Correct Answer: C

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Question 18

A 25.0 mL sample of 0.100 M HCl(aq) is titrated with 0.100 M NaOH(aq). What is the volume of NaOH(aq) required to reach the equivalence point?

A. 25.0 mL

Correct B. 50.0 mL

C. 75.0 mL

D. 100 mL

Correct Answer: B

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Question 19

A 1.00 g sample of a metal is heated in a crucible to produce a 0.500 g sample of the metal oxide. What is the percentage yield of the metal oxide?

A. 50.0%

Correct B. 75.0%

C. 80.0%

D. 90.0%

Correct Answer: B

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Question 20

Determine the number of moles of oxygen gas (O2) required to completely combust 2.50 moles of propane (C3H8) according to the balanced equation: 2C3H8 + 19O2 → 12CO2 + 14H2O.

Correct A. 1.25 moles

B. 2.50 moles

C. 3.75 moles

D. 5.00 moles

Correct Answer: A

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Question 21

A sample of nitrogen gas (N2) is collected over water at a temperature of 25°C and a pressure of 1.00 atm. If the vapor pressure of water at 25°C is 0.0313 atm, calculate the partial pressure of nitrogen gas.

A. 0.9687 atm

Correct B. 0.9697 atm

C. 0.9710 atm

D. 0.9723 atm

Correct Answer: B

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Question 22

The s\tandard enthalpy of formation of carbon dioxide (CO2) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of combustion of 1.00 mole of carbon (C) according to the equation: C + O2 → CO2.

Correct A. -393.5 kJ

B. -394.5 kJ

C. -395.5 kJ

D. -396.5 kJ

Correct Answer: A

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Question 23

A 2.00 M solution of sulfuric acid (H2SO4) is mixed with 1.00 M solution of sodium hydroxide (NaOH). If the reaction is complete, calculate the concentration of the resulting solution.

A. 1.00 M

Correct B. 1.50 M

C. 2.00 M

D. 2.50 M

Correct Answer: B

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Question 24

A sample of air contains 21.0% oxygen (O2) by volume. If the air is compressed to a pressure of 10.0 atm, calculate the partial pressure of oxygen gas.

A. 2.10 atm

Correct B. 2.20 atm

C. 2.30 atm

D. 2.40 atm

Correct Answer: B

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Question 25

A 1.00 L sample of a 0.500 M solution of sodium chloride (NaCl) is mixed with 2.00 L of a 0.250 M solution of calcium chloride (CaCl2). If the reaction is complete, calculate the concentration of the resulting solution.

A. 0.125 M

B. 0.250 M

Correct C. 0.375 M

D. 0.500 M

Correct Answer: C

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