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POST UTME ELIZADE UNIVERSITY 2018 Chemistry | Objective

Are you preparing for POST UTME ELIZADE UNIVERSITY exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2018 Chemistry (Objective) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1

Determine the number of unpaired electrons in the ground state of a neutral copper atom.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 2

A 2.5 g sample of a metal carbonate is treated with 20 mL of 0.5 M HCl. If 10 mL of the excess HCl requires 12.5 mL of 0.1 M NaOH for neutralization, calculate the molar mass of the metal carbonate.

A. 100 g/mol

B. 120 g/mol

Correct C. 150 g/mol

D. 180 g/mol

Correct Answer: C

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Question 3

The diagram below shows a setup for electrolysis of a solution of an acid. Identify the product formed at the cathode.

Correct A. H2

B. O2

C. H2O

D. Acid

Correct Answer: A

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Question 4

A 0.1 M solution of a weak acid (HA) is 10% ionized at 25°C. If the dissociation cons\tant (Ka) of the acid is 1.0 x 10^-5, calculate the pH of the solution.

A. 2.0

Correct B. 2.5

C. 3.0

D. 3.5

Correct Answer: B

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Question 5

The diagram below shows a setup for a titration experiment. Identify the subs\tance being titrated.

A. Acid

Correct B. Base

C. Salt

D. Water

Correct Answer: B

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Question 6

A solution of sodium chloride (NaCl) is prepared by dissolving 35.5 g of NaCl in 100 mL of water. What is the molar concentration of the solution?

A. 0.5 M

Correct B. 1.0 M

C. 1.5 M

D. 2.0 M

Correct Answer: B

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Question 7

A sample of a polymer is analyzed u\sing gel permeation chromatography (GPC). The chromatogram shows a \single peak with a retention time of 12.5 minutes. What is the molecular weight of the polymer?

A. 10,000 g/mol

B. 50,000 g/mol

Correct C. 100,000 g/mol

D. 500,000 g/mol

Correct Answer: C

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Question 8

A redox reaction is represented by the equation: 2Fe^{2+} + MnO_4^- + 6H^+ → 2Fe^{3+} + Mn^{2+} + 3H_2O. What is the oxidation state of the manganese ion in the product?

A. +2

Correct B. +3

C. +4

D. +5

Correct Answer: B

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Question 9

A sample of air is collected over water and analyzed u\sing gas chromatography. The chromatogram shows three peaks with retention times of 5.2, 8.1, and 12.5 minutes. What is the composition of the air sample?

Correct A. N_2 (5.2 min), O_2 (8.1 min), CO_2 (12.5 min)

B. N_2 (5.2 min), O_2 (8.1 min), H_2 (12.5 min)

C. N_2 (5.2 min), CO_2 (8.1 min), H_2 (12.5 min)

D. O_2 (5.2 min), CO_2 (8.1 min), H_2 (12.5 min)

Correct Answer: A

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Question 10

A solution of sulfuric acid \( H_2SO_4 \) is prepared by dissolving 50.0 g of H_2SO_4 in 100 mL of water. What is the molarity of the solution?

A. 1.0 M

Correct B. 2.0 M

C. 3.0 M

D. 4.0 M

Correct Answer: B

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Question 11

Determine the molar mass of a polymer with the following composition: 60% polyethylene (C2H4), 20% polypropylene (C3H6), and 20% polystyrene (C8H8).

A. 60 g/mol

B. 120 g/mol

Correct C. 180 g/mol

D. 240 g/mol

Correct Answer: C

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Question 12

A 2.5 M solution of NaOH is mixed with a 1.0 M solution of HCl. What is the resulting concentration of the solution after the reaction is complete?

A. 1.25 M

B. 2.5 M

Correct C. 3.75 M

D. 5.0 M

Correct Answer: C

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Question 13

A sample of 2-propanol (C3H8O) has a density of 0.785 g/mL. What is the volume of 25.0 g of this subs\tance?

A. 32.0 mL

Correct B. 40.0 mL

C. 48.0 mL

D. 56.0 mL

Correct Answer: B

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Question 14

A 10.0 g sample of a subs\tance is dissolved in 50.0 mL of water. What is the concentration of the solution in g/L?

A. 0.2 g/L

B. 0.4 g/L

Correct C. 0.6 g/L

D. 0.8 g/L

Correct Answer: C

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Question 15

A 5.0 M solution of HCl is mixed with a 2.0 M solution of NaOH. What is the resulting concentration of the solution after the reaction is complete?

A. 2.5 M

B. 3.0 M

Correct C. 3.75 M

D. 5.0 M

Correct Answer: C

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Question 16

Determine the s\tandard Gibbs free energy change (ΔG°) for the reaction: 2Ag+(aq) + 2Cl-(aq) → 2AgCl(s) at 298 K, given that the s\tandard enthalpy change (ΔH°) is -127.5 kJ/mol and the s\tandard entropy change (ΔS°) is -173.5 J/mol·K.

A. -127.5 kJ/mol

B. -173.5 J/mol·K

Correct C. -127.5 kJ/mol + 298 K × -173.5 J/mol·K

D. -127.5 kJ/mol - 298 K × -173.5 J/mol·K

Correct Answer: C

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Question 17

A 2.5-g sample of a metal oxide (M2O3) is heated in a stream of hydrogen gas. The reaction is: M2O3(s) + 3H2(g) → 2MO(s) + 3H2O(l). If 2.5 L of hydrogen gas at 25°C and 1 atm is consumed, calculate the molar mass of the metal oxide (M2O3).

A. 150 g/mol

B. 200 g/mol

Correct C. 250 g/mol

D. 300 g/mol

Correct Answer: C

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Question 18

The s\tandard enthalpy of formation (ΔHf°) for CO2(g) is -393.5 kJ/mol. The s\tandard enthalpy of formation (ΔHf°) for H2O(l) is -285.8 kJ/mol. Calculate the s\tandard enthalpy of formation (ΔHf°) for the reaction: CO(g) + H2(g) → CO2(g) + H2O(l).

Correct A. -679.3 kJ/mol

B. -679.3 kJ/mol + 393.5 kJ/mol

C. -679.3 kJ/mol - 393.5 kJ/mol

D. -679.3 kJ/mol + 285.8 kJ/mol

Correct Answer: A

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Question 19

A 0.500 M solution of NaOH is mixed with a 0.500 M solution of HCl. Calculate 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 20

A 1.00-g sample of a metal (M) is dissolved in 10.0 mL of 1.00 M HNO3. The resulting solution is then diluted to 100.0 mL. If the concentration of the metal ion \( M3+ \) in the resulting solution is 0.500 M, calculate the molar mass of the metal (M).

A. 50.0 g/mol

Correct B. 100 g/mol

C. 150 g/mol

D. 200 g/mol

Correct Answer: B

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Question 21

A 2.5 g sample of a non-metallic oxide of nitrogen is heated in a stream of hydrogen gas. The resulting gas is passed through a solution of sodium hydroxide, and the volume of the gas collected is 2.5 liters at 25°C and 1 atm. What is the empirical formula of the oxide?

A. N2O

Correct B. NO

C. N2O3

D. N2O5

Correct Answer: B

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Question 22

A solution of sodium hydroxide is titrated with a solution of hydrochloric acid. The initial pH of the sodium hydroxide solution is 12.0. After the addition of 25.0 mL of hydrochloric acid, the pH of the solution is 10.5. What is the concentration of the hydrochloric acid solution?

A. 0.100 M

B. 0.200 M

Correct C. 0.500 M

D. 1.00 M

Correct Answer: C

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Question 23

A 2.0 g sample of a polymer is dissolved in 100 mL of a solvent. The solution is then titrated with a solution of a strong acid. The initial pH of the solution is 7.0. After the addition of 10.0 mL of the acid solution, the pH of the solution is 4.0. What is the molecular weight of the polymer?

A. 1000 g/mol

Correct B. 2000 g/mol

C. 5000 g/mol

D. 10,000 g/mol

Correct Answer: B

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Question 24

A 1.0 g sample of a non-metallic oxide of sulfur is heated in a stream of oxygen gas. The resulting gas is passed through a solution of sodium hydroxide, and the volume of the gas collected is 1.5 liters at 25°C and 1 atm. What is the empirical formula of the oxide?

A. SO2

Correct B. SO3

C. S2O3

D. S2O6

Correct Answer: B

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Question 25

A solution of sodium hydroxide is titrated with a solution of hydrochloric acid. The initial pH of the sodium hydroxide solution is 12.0. After the addition of 20.0 mL of hydrochloric acid, the pH of the solution is 10.0. What is the concentration of the hydrochloric acid solution?

A. 0.050 M

B. 0.100 M

Correct C. 0.200 M

D. 0.500 M

Correct Answer: C

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