POST UTME UNIBEN 2023 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
Determine the molar mass of a polymer with the repeating unit (C6H4)2(CO)2.
A. 120 g/mol
B. 180 g/mol
C. 240 g/mol
D. 300 g/mol
Question 2
Determine the number of moles of oxygen gas (O2) required to completely combust 2.5 moles of propane (C3H8) according to the balanced equation: C3H8 + 5O2 → 3CO2 + 4H2O.
A. 10 moles
B. 5 moles
C. 15 moles
D. 20 moles
Question 3
The half-life of a radioactive subs\tance is 10 years. If the initial activity is 1000 Bq, calculate the activity after 20 years.
A. 100 Bq
B. 200 Bq
C. 500 Bq
D. 1000 Bq
Question 4
The s\tandard reduction potential of the Cu2+/Cu couple is +0.34 V. Calculate the s\tandard cell potential for a cell consisting of a Cu2+/Cu couple in the anode and a Zn2+/Zn couple in the cathode.
A. +0.10 V
B. +0.20 V
C. +0.30 V
D. +0.40 V
Question 5
The atomic radius of an element in the periodic table increases down a group due to the addition of new energy levels. However, this tr\end is disrupted in the case of the noble gases. Explain the reason behind this disruption.
A. The noble gases have a full outer energy level, making it difficult for them to form compounds and thus disrupting the tr\end.
B. The noble gases have a higher atomic radius due to the presence of more protons in their nucleus.
C. The noble gases have a lower atomic radius due to the presence of more electrons in their outer energy level.
D. The noble gases have a unique electronic configuration that makes them resis\tant to changes in atomic radius.
Question 6
The boiling point of an organic compound is 120°C. If the compound is a mixture of 60% hexane and 40% toluene, calculate the boiling point of the mixture.
A. 110°C
B. 115°C
C. 120°C
D. 125°C
Question 7
A strong acid is defined as an acid that completely dissociates in water to produce hydrogen ions. What is the pH of a 0.1 M solution of hydrochloric acid (HCl)?
A. 1
B. 2
C. 3
D. 4
Question 8
A polymer is a large molecule composed of many repeated subunits called monomers. What is the primary function of a polymer in a bio\logical system?
A. To provide structural support to cells and tissues.
B. To facilitate the transport of nutrients and waste products across cell membranes.
C. To regulate the activity of enzymes and other biomolecules.
D. To store genetic information in the form of DNA.
Question 9
A 2.0 g sample of a polymer is dissolved in 100 mL of solvent. The osmotic pressure of the solution is 1.5 atm. Calculate the molar mass of the polymer.
A. 100 g/mol
B. 200 g/mol
C. 500 g/mol
D. 1000 g/mol
Question 10
A polymer has a molecular weight of 50,000 g/mol and a degree of polymerization of 500. What is the molar mass of the repeating unit?
A. 100 g/mol
B. 500 g/mol
C. 1000 g/mol
D. 5000 g/mol
Question 11
In the electrolysis of a molten ionic compound, what is the primary function of the inert anode?
A. To facilitate the flow of electrons from the anode to the cathode
B. To prevent the anode from dissolving in the electrolyte
C. To increase the rate of reaction at the anode
D. To reduce the voltage required for electrolysis
Question 12
The reaction of hydrogen gas with oxygen gas is represented by the equation: 2H2(g) + O2(g) → 2H2O(l). What is the oxidation state of oxygen in the product H2O(l)?
A. -2
B. +1
C. +2
D. 0
Question 13
A solution containing 0.1 M HCl and 0.1 M NaOH is prepared. What is the concentration of the resulting solution after complete neutralization?
A. 0.1 M
B. 0.05 M
C. 0.01 M
D. 0.001 M
Question 14
The rate cons\tant of a first-order reaction is given by the equation: k = 2.303/t \log[A]0/[A]t. If the initial concentration of the reac\tant is 0.1 M and the concentration at time t is 0.01 M, calculate the rate cons\tant k.
A. 0.0001 s^-1
B. 0.001 s^-1
C. 0.01 s^-1
D. 0.1 s^-1
Question 15
A 2.50 L sample of a gas at 27°C and 1.00 atm is collected over water at 25°C. If the vapor pressure of water at 25°C is 23.8 mmHg, what is the partial pressure of the gas?
A. 0.95 atm
B. 1.00 atm
C. 1.05 atm
D. 1.10 atm

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