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POST UTME NOUN 2025 Chemistry | Objective

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Question 1

The reaction 2Ag+(aq) + Cr(s) → 2Ag(s) + Cr2+(aq) is an example of a redox reaction. What is the oxidation state of chromium in the reac\tant?

A. 0

B. +2

Correct C. -2

D. +3

Correct Answer: C

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Question 2

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)?

Correct A. 1.0 x 10^\( -4 \) s^\( -1 \)

B. 1.0 x 10^\( -3 \) s^\( -1 \)

C. 1.0 x 10^\( -2 \) s^\( -1 \)

D. 1.0 x 10^\( -1 \) s^\( -1 \)

Correct Answer: A

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Question 3

A 2.0 M solution of HCl is mixed with a 2.0 M solution of NaOH. What is the concentration of the resulting solution?

A. 0.5 M

Correct B. 1.0 M

C. 2.0 M

D. 4.0 M

Correct Answer: B

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Question 4

The s\tandard enthalpy of formation (ΔHf) of CO2(g) is -393.5 kJ/mol. What is the s\tandard enthalpy of formation (ΔHf) of CO(g)?

Correct A. -110.5 kJ/mol

B. -393.5 kJ/mol

C. -74.8 kJ/mol

D. -247.4 kJ/mol

Correct Answer: A

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Question 5

A 1.0 M solution of HCl is mixed with a 1.0 M solution of NaOH. 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 6

Determine the s\tandard enthalpy of formation of NH3(g) from the following data: ΔHf(NH3(g)) = ?; ΔHf(H2(g)) = -285.8 kJ/mol; ΔHf(N2(g)) = 0 kJ/mol.

A. -45.9 kJ/mol

B. -92.1 kJ/mol

Correct C. -45.9 kJ/mol

D. -92.1 kJ/mol

Correct Answer: C

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Question 7

The reaction 2NO(g) + O2(g) → 2NO2(g) has a rate cons\tant of 0.05 s^-1 at 298 K. Calculate the rate of reaction at 298 K.

A. 0.1 mol L^-1 s^-1

Correct B. 0.05 mol L^-1 s^-1

C. 0.1 mol L^-1 s^-1

D. 0.05 mol L^-1 s^-1

Correct Answer: B

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Question 8

A 2.5 M solution of HCl is mixed with a 2.5 M solution of NaOH. Calculate the concentration of the resulting solution.

A. 2.5 M

Correct B. 5.0 M

C. 2.5 M

D. 5.0 M

Correct Answer: B

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Question 9

A 25 mL sample of 0.1 M NaOH is titrated with 0.1 M HCl. Calculate the volume of HCl required to reach the equivalence point.

A. 25 mL

Correct B. 50 mL

C. 25 mL

D. 50 mL

Correct Answer: B

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Question 10

A 100 mL sample of 0.5 M H2SO4 is mixed with a 100 mL sample of 0.5 M NaOH. Calculate the pH of the resulting solution.

A. 1

Correct B. 2

C. 1

D. 2

Correct Answer: B

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Question 11

Determine the type of reaction that occurs when 1-bu\tanol is heated with a strong base.

A. Substitution reaction

Correct B. Elimination reaction

C. Condensation reaction

D. Addition reaction

Correct Answer: B

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Question 12

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

Correct B. 2.5 atm

C. 3.5 atm

D. 4.5 atm

Correct Answer: B

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Question 13

A solution contains 2.0 g of NaCl in 100 mL of water. Calculate the molarity of the solution.

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 14

A 10.0 mL sample of a solution containing 0.5 M HCl is titrated with 0.1 M NaOH. Calculate the volume of NaOH required to reach the equivalence point.

A. 10.0 mL

Correct B. 20.0 mL

C. 30.0 mL

D. 40.0 mL

Correct Answer: B

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Question 15

A diagram of a titration setup is shown below.

Correct A. The burette contains NaOH.

B. The beaker contains HCl.

C. The burette contains HCl.

D. The beaker contains NaOH.

Correct Answer: A

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Question 16

The atomic radius of an element increases down a group in the periodic table due to the addition of new energy levels. However, the atomic radius of an element decreases across a period due to the increase in effective nuclear charge. Which of the following elements has the largest atomic radius?

A. Francium (Fr)

Correct B. Caesium (Cs)

C. Rubidium (Rb)

D. Potassium (K)

Correct Answer: B

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Question 17

A 2.5 M solution of sodium hydroxide (NaOH) is prepared by dissolving 12.5 g of NaOH in water to make 250 mL of solution. What is the concentration of the solution in moles per liter?

A. 0.1 M

Correct B. 0.2 M

C. 0.5 M

D. 1.0 M

Correct Answer: B

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Question 18

A sample of air contains 21% oxygen, 78% nitrogen, and 1% other gases. What is the partial pressure of oxygen in a sample of air at 1 atm total pressure?

Correct A. 0.21 atm

B. 0.21 kPa

C. 0.21 bar

D. 0.21 MPa

Correct Answer: A

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Question 19

A 10.0 g sample of sulfur (S) is burned in oxygen to produce sulfur dioxide (SO2). If the reaction is 100% efficient, what is the volume of SO2 produced at STP?

A. 22.4 L

Correct B. 44.8 L

C. 67.2 L

D. 89.6 L

Correct Answer: B

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Question 20

A 1.0 M solution of hydrochloric acid (HCl) is prepared by dissolving 36.5 g of HCl in water to make 1 L of solution. What is the pH of the solution?

A. 0.5

Correct B. 1.0

C. 2.0

D. 3.0

Correct Answer: B

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Question 21

The reaction of zinc metal with hydrochloric acid is represented by the equation: Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g). What is the oxidation state of zinc in this reaction?

A. 0

Correct B. +2

C. -2

D. +1

Correct Answer: B

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Question 22

A solution of sodium hydroxide (NaOH) is mixed with a solution of acetic acid (CH3COOH). The reaction is represented by the equation: NaOH(aq) + CH3COOH(aq) → CH3COONa(aq) + H2O(l). 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

A sample of copper metal is electrolyzed in a solution of copper(II) sulfate. The reaction is represented by the equation: Cu(s) + Cu2+(aq) → 2Cu+(aq). What is the mass of copper deposited at the cathode after 2 hours of electrolysis?

A. 10 g

Correct B. 20 g

C. 30 g

D. 40 g

Correct Answer: B

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Question 24

A solution of potassium permanganate (KMnO4) is added to a solution of oxalic acid (H2C2O4). The reaction is represented by the equation: 2KMnO4(aq) + 5H2C2O4(aq) + 3H2SO4(aq) → K2SO4(aq) + 2MnSO4(aq) + 10CO2(g) + 8H2O(l). What is the number of moles of oxalic acid required to react with 2 moles of potassium permanganate?

A. 2 moles

Correct B. 3 moles

C. 4 moles

D. 5 moles

Correct Answer: B

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Question 25

A sample of hydrogen gas is collected over water at a temperature of 25°C and a pressure of 1 atm. What is the volume of the hydrogen gas at s\tandard temperature and pressure (STP)?

Correct A. 22.4 L

B. 44.8 L

C. 67.2 L

D. 89.6 L

Correct Answer: A

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