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POST UTME UNIPORT 2019 Chemistry | Objective

Are you preparing for POST UTME UNIPORT exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2019 Chemistry (Objective) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1

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.

Correct A. -46.1 kJ/mol

B. -92.2 kJ/mol

C. -46.1 kJ/mol

D. -92.2 kJ/mol

Correct Answer: A

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Question 2

A 0.500 M solution of NaOH is titrated with 0.500 M HCl. Calculate the pH of the solution after 25.0 mL of HCl has been added.

A. 2.00

Correct B. 3.00

C. 4.00

D. 5.00

Correct Answer: B

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Question 3

A diagram of a titration setup is shown below. If 25.0 mL of 0.500 M HCl is added to 25.0 mL of 0.500 M NaOH, what is the pH of the resulting solution?

A. 2.00

Correct B. 3.00

C. 4.00

D. 5.00

Correct Answer: B

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Question 4

A 0.100 M solution of H2S is titrated with 0.100 M Ba(OH)2. Calculate the pH of the solution after 50.0 mL of Ba(OH)2 has been added.

A. 1.00

B. 2.00

C. 3.00

Correct D. 4.00

Correct Answer: D

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Question 5

A diagram of a titration setup is shown below. If 25.0 mL of 0.500 M HCl is added to 25.0 mL of 0.500 M NaOH, what is the pH of the resulting solution?

A. 2.00

Correct B. 3.00

C. 4.00

D. 5.00

Correct Answer: B

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Question 6

Determine the major product of the reaction between 2-methylpropene and HCl.

Correct A. 2-chloro-2-methylpropane

B. 2-chloro-2-methylbu\tane

C. 2-chloro-3-methylbu\tane

D. 2-chloro-3-methylpen\tane

Correct Answer: A

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Question 7

Calculate the equilibrium cons\tant (Kc) for the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g), given that at equilibrium, [N2] = 0.2 M, [H2] = 0.6 M, and [NH3] = 0.8 M.

A. 0.25

B. 0.50

Correct C. 1.00

D. 2.00

Correct Answer: C

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Question 8

A 2.5 L flask contains 0.5 mol of an ideal gas at a temperature of 300 K. Calculate the pressure of the gas u\sing the ideal gas law.

A. 1.0 atm

Correct B. 2.0 atm

C. 3.0 atm

D. 4.0 atm

Correct Answer: B

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Question 9

A solution contains 10 g of NaCl in 100 g of water. Calculate the molality 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 10

A 25 mL sample of a colloidal solution contains 0.5 g of particles. Calculate the concentration of the particles in the solution.

A. 0.02 g/mL

Correct B. 0.04 g/mL

C. 0.06 g/mL

D. 0.08 g/mL

Correct Answer: B

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Question 11

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.

Correct A. -46.1 kJ/mol

B. -92.2 kJ/mol

C. -46.1 kJ/mol

D. -92.2 kJ/mol

Correct Answer: A

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Question 12

Calculate the s\tandard Gibbs free energy change for the reaction: 2Al(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 3H2(g).

Correct A. -1.2 x 10^3 J/mol

B. -1.2 x 10^3 J/mol

C. -1.2 x 10^3 J/mol

D. -1.2 x 10^3 J/mol

Correct Answer: A

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Question 13

The s\tandard electrode potential for the reaction: Zn(s) → Zn2+(aq) + 2e- is -0.76 V. What is the s\tandard electrode potential for the reaction: Zn2+(aq) + 2e- → Zn(s)?

A. 0.76 V

Correct B. -0.76 V

C. 0.76 V

D. -0.76 V

Correct Answer: B

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Question 14

A 2.50 g sample of sulfur is burned in oxygen to produce sulfur dioxide. If 1.25 g of sulfur dioxide is collected, what is the percentage yield of sulfur dioxide?

A. 50%

B. 75%

Correct C. 50%

D. 75%

Correct Answer: C

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Question 15

A solution contains 0.250 M HCl and 0.250 M NaOH. What is the pH of the solution after mixing?

A. 1.00

Correct B. 2.00

C. 1.00

D. 2.00

Correct Answer: B

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Question 16

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 0.05 M, respectively, and the rate of reaction is 0.02 M/s after 10 minutes.

Correct A. \( k = \frac{2.303}{t} \log \frac{[NO]_0 [O_2]_0}{[NO_2]_t} \)

B. \( k = \frac{1}{t} \log \frac{[NO]_0 [O_2]_0}{[NO_2]_t} \)

C. \( k = \frac{2.303}{t} \log \frac{[NO]_t [O_2]_t}{[NO_2]_0} \)

D. \( k = \frac{1}{t} \log \frac{[NO]_t [O_2]_t}{[NO_2]_0} \)

Correct Answer: A

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Question 17

A sample of 1.0 g of a polymer is dissolved in 100 mL of a solvent. The osmotic pressure of the solution is found to be 1.5 atm at 25°C. Calculate the molar mass of the polymer.

Correct A. \( M = \frac{RT}{P} \)

B. \( M = \frac{P}{RT} \)

C. \( M = \frac{RT}{P} + \frac{P}{RT} \)

D. \( M = \frac{P}{RT} - \frac{RT}{P} \)

Correct Answer: A

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Question 18

A 2.0 M solution of NaOH is mixed with a 2.0 M solution of HCl. The resulting solution is found to be 1.0 M. Calculate the initial concentrations of NaOH and HCl.

A. \( [NaOH]_0 = 1.0 M \) and \( [HCl]_0 = 1.0 M \)

Correct B. \( [NaOH]_0 = 2.0 M \) and \( [HCl]_0 = 2.0 M \)

C. \( [NaOH]_0 = 1.0 M \) and \( [HCl]_0 = 2.0 M \)

D. \( [NaOH]_0 = 2.0 M \) and \( [HCl]_0 = 1.0 M \)

Correct Answer: B

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Question 19

A 1.0 M solution of CH3OH is mixed with a 1.0 M solution of HCl. The resulting solution is found to be 1.0 M. Calculate the initial concentrations of CH3OH and HCl.

Correct A. \( [CH_3OH]_0 = 1.0 M \) and \( [HCl]_0 = 1.0 M \)

B. \( [CH_3OH]_0 = 2.0 M \) and \( [HCl]_0 = 2.0 M \)

C. \( [CH_3OH]_0 = 1.0 M \) and \( [HCl]_0 = 2.0 M \)

D. \( [CH_3OH]_0 = 2.0 M \) and \( [HCl]_0 = 1.0 M \)

Correct Answer: A

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Question 20

A 1.0 M solution of NaOH is mixed with a 1.0 M solution of HCl. The resulting solution is found to be 1.0 M. Calculate the initial concentrations of NaOH and HCl.

Correct A. \( [NaOH]_0 = 1.0 M \) and \( [HCl]_0 = 1.0 M \)

B. \( [NaOH]_0 = 2.0 M \) and \( [HCl]_0 = 2.0 M \)

C. \( [NaOH]_0 = 1.0 M \) and \( [HCl]_0 = 2.0 M \)

D. \( [NaOH]_0 = 2.0 M \) and \( [HCl]_0 = 1.0 M \)

Correct Answer: A

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Question 21

The rate cons\tant of a first-order reaction is 0.05 min^-1. If the initial concentration of the reac\tant is 0.1 M, what is the concentration after 10 minutes?

A. 0.01 M

Correct B. 0.02 M

C. 0.03 M

D. 0.04 M

Correct Answer: B

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Question 22

A solution of 0.1 M NaCl is prepared by dissolving 0.1 g of NaCl in 100 mL of water. What is the molarity of the solution?

Correct A. 0.1 M

B. 0.2 M

C. 0.3 M

D. 0.4 M

Correct Answer: A

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Question 23

The s\tandard electrode potential of the Zn^2+/Zn couple is -0.76 V. What is the s\tandard electrode potential of the Cu^2+/Cu couple if the cell potential is 0.44 V?

A. -0.20 V

B. -0.30 V

Correct C. -0.40 V

D. -0.50 V

Correct Answer: C

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Question 24

The enthalpy of combustion of methane is -890 kJ/mol. What is the enthalpy of combustion of 1 mole of ethane?

A. -1.32 MJ/mol

Correct B. -1.42 MJ/mol

C. -1.52 MJ/mol

D. -1.62 MJ/mol

Correct Answer: B

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Question 25

A 2.0 g sample of a hydrocarbon is burned in a bomb calorimeter, relea\sing 12.5 kJ of heat. What is the molar mass of the hydrocarbon?

A. 20 g/mol

B. 30 g/mol

Correct C. 40 g/mol

D. 50 g/mol

Correct Answer: C

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