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POST UTME UNILAG 2018 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 2018 Chemistry (Objective) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1

The reaction of cyclopropane with chlorine gas in the presence of light produces a mixture of products. Which of the following is the major product?

Correct A. 1,2-dichlorocyclopropane

B. 1,3-dichlorocyclopropane

C. trans-1,2-dichlorocyclopropane

D. cis-1,2-dichlorocyclopropane

Correct Answer: A

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Question 2

The reaction of sulfur with oxygen gas produces sulfur dioxide gas. What is the balanced chemical equation for this reaction?

Correct A. S + O2 → SO2

B. S + O2 → SO3

C. S + O2 → SO4

D. S + O2 → SO5

Correct Answer: A

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Question 3

The diagram below shows a titration setup. What is the purpose of the burette?

Correct A. To measure the volume of the acid

B. To measure the volume of the base

C. To mix the acid and base

D. To measure the pH of the solution

Correct Answer: A

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Question 4

The reaction of sodium hydroxide with hydrochloric acid produces sodium chloride and water. What is the balanced chemical equation for this reaction?

Correct A. NaOH + HCl → NaCl + H2O

B. NaOH + HCl → NaCl + O2

C. NaOH + HCl → NaCl + CO2

D. NaOH + HCl → NaCl + SO2

Correct Answer: A

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Question 5

The diagram below shows a circuit setup. What is the purpose of the resistor?

Correct A. To reduce the voltage of the circuit

B. To increase the current of the circuit

C. To measure the voltage of the circuit

D. To measure the current of the circuit

Correct Answer: A

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Question 6

Determine the structure of the compound formed by the reaction of 2-methylpropane with chlorine gas in the presence of light.

A. CH₃CH₂CH₂Cl

Correct B. (CH₃)₃CCl

C. CH₃CH₂CH₂CH₂Cl

D. (CH₃)₂CHCH₂Cl

Correct Answer: B

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Question 7

A sample of a non-metallic oxide, X₂O₃, is found to have a mass of 0.250 g and a volume of 0.500 mL. What is the molar mass of the oxide?

A. 100.0 g/mol

Correct B. 150.0 g/mol

C. 200.0 g/mol

D. 250.0 g/mol

Correct Answer: B

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Question 8

A solution of 0.100 M NaOH is mixed with a solution of 0.100 M HCl. What is the concentration of the resulting solution?

A. 0.0500 M

B. 0.100 M

Correct C. 0.150 M

D. 0.200 M

Correct Answer: C

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Question 9

A 2.00 L flask contains 0.500 mol of a gas at 25°C. What is the pressure of the gas?

A. 1.00 atm

Correct B. 2.00 atm

C. 3.00 atm

D. 4.00 atm

Correct Answer: B

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Question 10

A 0.500 g sample of a polymer is dissolved in 100 mL of a solvent. What is the concentration of the solution?

A. 0.500 g/100 mL

Correct B. 1.00 g/100 mL

C. 1.50 g/100 mL

D. 2.00 g/100 mL

Correct Answer: B

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Question 11

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

A. Potassium (K)

B. Sodium (Na)

C. Rubidium (Rb)

Correct D. Caesium (Cs)

Correct Answer: D

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Question 12

A solution of 0.1 M NaOH is titrated with 0.1 M HCl. The pH of the solution at the equivalence point is 7. What is the pH of the solution at the half-equivalence point?

A. 6.0

Correct B. 6.5

C. 7.0

D. 7.5

Correct Answer: B

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Question 13

A sample of water contains 0.1 g/L of dissolved oxygen. What is the concentration of dissolved oxygen in moles per liter?

Correct A. 1.0 x 10^-3 M

B. 1.0 x 10^-4 M

C. 1.0 x 10^-5 M

D. 1.0 x 10^-6 M

Correct Answer: A

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Question 14

The diagram below shows a titration setup. What is the purpose of the burette?

Correct A. To measure the volume of the titrant

B. To measure the volume of the analyte

C. To mix the titrant and analyte

D. To separate the titrant and analyte

Correct Answer: A

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Question 15

A solution of 0.1 M HCl is titrated with 0.1 M NaOH. The pH of the solution at the equivalence point is 7. What is the pH of the solution at the half-equivalence point?

A. 6.0

Correct B. 6.5

C. 7.0

D. 7.5

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 0.5 M and 0.2 M, respectively, and the rate of reaction is 0.02 M/s after 10 minutes.

Correct A. \( k = \frac{2.303}{t} \log \frac{[NO]_0^2 [O_2]_0}{[NO_2]^2} \)

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

C. \( k = \frac{2.303}{t} \log \frac{[NO]_0 [O_2]_0^2}{[NO_2]^2} \)

D. \( k = \frac{2.303}{t} \log \frac{[NO]_0^2 [O_2]_0}{[NO_2]} \)

Correct Answer: A

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Question 17

A mixture of 2.5 g of an unknown hydrocarbon and 2.5 g of an unknown ha\logen was ignited, producing 5.0 g of a gaseous product. The gaseous product was then passed through a solution of KOH, resulting in the formation of 2.5 g of water. What is the empirical formula of the unknown hydrocarbon?

Correct A. C2H6

B. C3H8

C. C4H10

D. C5H12

Correct Answer: A

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Question 18

A solution of 0.1 M NaOH was slowly added to a solution of 0.1 M HCl. The initial rate of reaction was 0.02 M/s. After 10 minutes, the rate of reaction had decreased to 0.01 M/s. What is the order of the reaction with respect to HCl?

A. 1st order

B. 2nd order

C. 3rd order

Correct D. Zero order

Correct Answer: D

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Question 19

A sample of a non-metallic element was heated in a stream of oxygen gas. The resulting product was a white solid that was soluble in water. What is the identity of the non-metallic element?

Correct A. Sulfur

B. Phosphorus

C. Chlorine

D. Bromine

Correct Answer: A

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Question 20

A 1.0 M solution of a weak acid (HA) was mixed with a 1.0 M solution of a strong base (NaOH). The resulting solution had a pH of 4.5. What is the value of the acid dissociation cons\tant (Ka) for the weak acid?

Correct A. \( 1.0 \times 10^{-4} \)

B. \( 1.0 \times 10^{-5} \)

C. \( 1.0 \times 10^{-6} \)

D. \( 1.0 \times 10^{-7} \)

Correct Answer: A

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Question 21

The reaction between benzene and chlorine in the presence of light produces a mixture of chlorinated benzenes. The major product is chlorobenzene. What is the structure of chlorobenzene?

Correct A. C6H5Cl

B. C6H5HCl

C. C6H5Cl2

D. C6H5Cl3

Correct Answer: A

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Question 22

A 2.5-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 1.8 g. What is the percentage yield of the metal oxide?

A. 80%

B. 85%

Correct C. 90%

D. 95%

Correct Answer: C

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Question 23

The equilibrium cons\tant (Kc) for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g) is 0.05 at 500 K. What is the equilibrium concentration of NH3 if the initial concentrations of N2 and H2 are 0.1 M and 0.3 M, respectively?

A. 0.02 M

Correct B. 0.04 M

C. 0.06 M

D. 0.08 M

Correct Answer: B

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Question 24

A 25-mL sample of a 0.1 M solution of NaOH is mixed with 25 mL of a 0.1 M solution of HCl. 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 25

A diagram of a titration setup is shown below. If 25 mL of 0.1 M NaOH is required to reach the equivalence point, what is the concentration of the HCl solution?

A. 0.05 M

Correct B. 0.1 M

C. 0.2 M

D. 0.5 M

Correct Answer: B

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