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POST UTME UNIBEN 2018 Chemistry | Objective

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Question 1

Determine the molar mass of a gas that occupies 2.5 L at 27°C and 1.0 atm.

A. 20 g/mol

Correct B. 30 g/mol

C. 40 g/mol

D. 50 g/mol

Correct Answer: B

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Question 2

What is the major product of the reaction between 2-bromopropane and sodium hydroxide?

A. 2-propanol

B. 2-bromo-2-methylpropane

Correct C. 2-methyl-2-propanol

D. 2-methyl-2-propanol and 2-bromo-2-methylpropane

Correct Answer: C

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Question 3

A metal sample has a density of 8.5 g/cm³ and a mass of 25.0 g. What is the volume of the metal sample?

A. 2.9 cm³

Correct B. 3.0 cm³

C. 3.1 cm³

D. 3.2 cm³

Correct Answer: B

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Question 4

What is the pH of a 0.10 M solution of HCl?

A. 0.10

Correct B. 1.0

C. 2.0

D. 3.0

Correct Answer: B

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Question 5

A 2.5 L sample of a gas at 27°C and 1.0 atm is collected over water at 25°C. What is the partial pressure of the gas?

A. 0.95 atm

Correct B. 1.0 atm

C. 1.05 atm

D. 1.1 atm

Correct Answer: B

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Question 6

The reaction of cyclohexane with bromine in the presence of light is an example of a ______________ reaction.

A. substitution reaction

B. elimination reaction

Correct C. addition reaction

D. oxidation reaction

Correct Answer: C

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Question 7

The solubility of a subs\tance in water is influenced by the ______________ of the subs\tance.

A. molecular weight

B. polarity

Correct C. intermolecular forces

D. temperature

Correct Answer: C

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Question 8

The reaction of zinc with copper(II) sulfate is an example of a ______________ reaction.

Correct A. displacement reaction

B. double displacement reaction

C. precipitation reaction

D. neutralization reaction

Correct Answer: A

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Question 9

The energy level of an electron in a hydrogen atom is given by the equation ______________.

Correct A. \( E_n = -\frac{13.6}{n^2} \) eV

B. \( E_n = \frac{13.6}{n^2} \) eV

C. \( E_n = -\frac{6.8}{n^2} \) eV

D. \( E_n = \frac{6.8}{n^2} \) eV

Correct Answer: A

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Question 10

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

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 11

A sample of hydrogen gas is collected over water at a temperature of 298 K and a pressure of 1.00 atm. If the partial pressure of water vapor is 0.0313 atm, calculate the mole \fraction of hydrogen gas in the sample.

Correct A. 0.999

B. 0.9999

C. 0.99999

D. 0.999999

Correct Answer: A

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Question 12

A solution contains 0.500 M HCl and 0.250 M NaOH. What is the pH of the solution after the reaction is complete?

A. 0.500

Correct B. 1.000

C. 1.500

D. 2.000

Correct Answer: B

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Question 13

A metal (X) reacts with chlorine gas to form a white solid. The reaction is as follows: X + Cl_2 → XCl_2. If 2.50 g of X reacts with 1.00 g of Cl_2, what is the empirical formula of the product?

A. XCl

Correct B. XCl_2

C. XCl_3

D. XCl_4

Correct Answer: B

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Question 14

A 0.100 M solution of NaOH is titrated with 0.100 M HCl. What is the pH of the solution after 25.0 mL of HCl has been added?

A. 0.500

Correct B. 1.000

C. 1.500

D. 2.000

Correct Answer: B

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Question 15

A metal (X) reacts with oxygen gas to form a brown solid. The reaction is as follows: 4X + 3O_2 → 2X_2O_3. If 2.50 g of X reacts with 1.00 g of O_2, what is the empirical formula of the product?

Correct A. X_2O_3

B. X_2O_4

C. X_2O_5

D. X_2O_6

Correct Answer: A

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Question 16

Determine the s\tandard potential of the cell formed by the reaction: MnO4- + 8H+ + 5e- → Mn2+ + 4H2O. Given that the s\tandard potentials of MnO4- and Mn2+ are +1.23 V and -1.18 V, respectively.

A. +1.05 V

B. +1.18 V

Correct C. +1.23 V

D. +1.30 V

Correct Answer: C

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Question 17

Calculate the molar mass of a compound that contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. The atomic masses of carbon, hydrogen, and oxygen are 12.01 g/mol, 1.008 g/mol, and 16.00 g/mol, respectively.

A. 60.0 g/mol

B. 80.0 g/mol

Correct C. 100.0 g/mol

D. 120.0 g/mol

Correct Answer: C

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Question 18

A 2.50 L flask contains 0.500 mol of an ideal gas at 25°C. Calculate the pressure of the gas u\sing the ideal gas law.

A. 1.01 atm

Correct B. 2.02 atm

C. 3.03 atm

D. 4.04 atm

Correct Answer: B

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Question 19

A 250 mL sample of a solution containing 0.100 M NaCl is mixed with 250 mL of a solution containing 0.100 M NaOH. Calculate 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 20

A 50.0 g sample of a metal oxide is heated in a crucible until it decomposes into its constituent elements. If the mass of the metal is 30.0 g, what is the mass of the oxygen in the sample?

A. 10.0 g

B. 20.0 g

C. 30.0 g

Correct D. 40.0 g

Correct Answer: D

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Question 21

Determine the s\tandard electrode potential for the reaction: MnO4- + 8H+ + 5e- → Mn2+ + 4H2O. Given that the s\tandard electrode potential for the reduction of MnO4- is +1.23 V.

A. +1.23 V

Correct B. +1.48 V

C. +1.93 V

D. +2.18 V

Correct Answer: B

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Question 22

A 2.5 L flask contains 0.5 mol of an ideal gas at 300 K. If the gas is heated to 400 K, what is the new volume of the gas?

A. 1.5 L

B. 2.5 L

Correct C. 3.5 L

D. 4.5 L

Correct Answer: C

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Question 23

A solution contains 0.1 M NaCl. What is the concentration of Cl- ions in the solution?

A. 0.05 M

Correct B. 0.1 M

C. 0.15 M

D. 0.2 M

Correct Answer: B

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Question 24

A 10 g sample of a polymer is dissolved in 100 mL of solvent. What is the concentration of the polymer solution in g/mL?

A. 0.1 g/mL

B. 0.5 g/mL

Correct C. 1 g/mL

D. 5 g/mL

Correct Answer: C

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Question 25

A reaction has a rate cons\tant of 2.5 s-1. If the initial concentration of the reac\tant is 0.5 M, what is the concentration after 10 s?

A. 0.2 M

B. 0.3 M

Correct C. 0.4 M

D. 0.5 M

Correct Answer: C

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