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POST UTME UNILAG 2019 Chemistry | Objective

Are you preparing for POST UTME UNILAG 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

The atomic number of an element is 26. What is the number of protons in the nucleus of an atom of this element?

A. 25

Correct B. 26

C. 27

D. 28

Correct Answer: B

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Question 2

A solution of 0.1 M HCl is titrated with 0.1 M NaOH. What is the pH of the solution after 20 mL of NaOH has been added?

A. 1

Correct B. 7

C. 9

D. 11

Correct Answer: B

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Question 3

A polymer has a molecular weight of 100,000 g/mol. If 1 g of the polymer is dissolved in 100 mL of water, what is the concentration of the solution in g/L?

A. 500

Correct B. 1000

C. 2000

D. 5000

Correct Answer: B

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Question 4

A redox reaction involves the oxidation of Fe2+ to Fe3+ and the reduction of MnO4- to Mn2+. What is the half-reaction for the oxidation of Fe2+?

A. Fe^{2+} \rightarrow Fe^{3+}

Correct B. Fe^{2+} \rightarrow Fe^{3+} + e^-

C. Fe^{3+} \rightarrow Fe^{2+}

D. Fe^{3+} \rightarrow Fe^{2+} + e^+

Correct Answer: B

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Question 5

A diagram of a titration setup is shown below. What is the purpose of the burette in this setup?

A. To measure the volume of the analyte

Correct B. To measure the volume of the titrant

C. To mix the analyte and titrant

D. To measure the pH of the solution

Correct Answer: B

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Question 6

Determine the rate cons\tant (k) for the reaction: 2NO(g) + O2(g) → 2NO2(g) at 298 K, given that the initial concentration of NO is 0.1 M and the concentration of NO2 is 0.05 M after 10 minutes.

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

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

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

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

Correct Answer: A

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Question 7

A 25 cm3 sample of 0.1 M HCl is titrated with 0.1 M NaOH. Calculate the pH of the solution after 20 cm3 of NaOH has been added.

Correct A. \( pH = \frac{1}{2} \log \frac{[HCl]_0}{[HCl]_t} \)

B. \( pH = \frac{1}{2} \log \frac{[HCl]_t}{[HCl]_0} \)

C. \( pH = \frac{1}{2} \log \frac{[HCl]_0}{[HCl]_t} + \frac{1}{2} \log \frac{[NaOH]_0}{[NaOH]_t} \)

D. \( pH = \frac{1}{2} \log \frac{[HCl]_t}{[HCl]_0} + \frac{1}{2} \log \frac{[NaOH]_t}{[NaOH]_0} \)

Correct Answer: A

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Question 8

The s\tandard electrode potential of the Zn2+/Zn couple is -0.76 V. Calculate the s\tandard electrode potential of the Cu2+/Cu couple if the s\tandard electrode potential of the Cu2+/Cu couple is -0.34 V.

Correct A. \( E^{circ}_{Cu^{2+}/Cu} = E^{circ}_{Zn^{2+}/Zn} - E^{circ}_{Cu^{2+}/Cu} \)

B. \( E^{circ}_{Cu^{2+}/Cu} = E^{circ}_{Zn^{2+}/Zn} + E^{circ}_{Cu^{2+}/Cu} \)

C. \( E^{circ}_{Cu^{2+}/Cu} = E^{circ}_{Zn^{2+}/Zn} - E^{circ}_{Cu^{2+}/Cu} \times \frac{[Zn^{2+}]}{[Cu^{2+}]} \)

D. \( E^{circ}_{Cu^{2+}/Cu} = E^{circ}_{Zn^{2+}/Zn} + E^{circ}_{Cu^{2+}/Cu} \times \frac{[Zn^{2+}]}{[Cu^{2+}]} \)

Correct Answer: A

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Question 9

A 1.0 g sample of a metal is heated in a crucible until it melts. The mass of the crucible and the metal is 1.5 g. The mass of the crucible alone is 0.5 g. Calculate the density of the metal.

Correct A. \( \rho = \frac{m}{V} \)

B. \( \rho = \frac{V}{m} \)

C. \( \rho = \frac{m}{V} \times \frac{V}{m} \)

D. \( \rho = \frac{V}{m} \times \frac{m}{V} \)

Correct Answer: A

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Question 10

A 2.0 M solution of HCl is titrated with 1.0 M NaOH. Calculate the pH of the solution after 20 cm3 of NaOH has been added.

Correct A. \( pH = \frac{1}{2} \log \frac{[HCl]_0}{[HCl]_t} \)

B. \( pH = \frac{1}{2} \log \frac{[HCl]_t}{[HCl]_0} \)

C. \( pH = \frac{1}{2} \log \frac{[HCl]_0}{[HCl]_t} + \frac{1}{2} \log \frac{[NaOH]_0}{[NaOH]_t} \)

D. \( pH = \frac{1}{2} \log \frac{[HCl]_t}{[HCl]_0} + \frac{1}{2} \log \frac{[NaOH]_t}{[NaOH]_0} \)

Correct Answer: A

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Question 11

The solubility of a subs\tance is defined as the maximum amount of the subs\tance that can dissolve in a given amount of solvent at a particular temperature. Which of the following statements is correct regarding the solubility of a subs\tance?

A. The solubility of a subs\tance is directly proportional to the temperature.

Correct B. The solubility of a subs\tance is inversely proportional to the pressure.

C. The solubility of a subs\tance is directly proportional to the volume of the solvent.

D. The solubility of a subs\tance is inversely proportional to the concentration of the solute.

Correct Answer: B

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Question 12

A solution contains 2.5 g of NaCl in 50 mL of water. What is the molarity of the solution?

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 13

The pH of a solution is 4. What is the concentration of hydrogen ions in the solution?

A. 10^{-4} M

B. 10^{-3} M

Correct C. 10^{-2} M

D. 10^{-1} M

Correct Answer: C

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Question 14

A sample of a hydrocarbon has a molecular formula of C_{4}H_{10}. What is the type of hydrocarbon?

Correct A. Alkane

B. Alkene

C. Alkyne

D. Aromatic hydrocarbon

Correct Answer: A

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Question 15

A solution contains 1.0 g of NaOH in 100 mL of water. What is the concentration of the solution?

A. 0.1 M

B. 0.2 M

Correct C. 0.5 M

D. 1.0 M

Correct Answer: C

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