POST UTME UNIBEN 2023 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
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 2
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 3
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 4
A solution of sodium hydroxide is added to a solution of copper(II) sulfate. What is the resulting solution?
A. A solution of sodium sulfate and copper(II) hydroxide
B. A solution of copper(II) hydroxide and sodium sulfate
C. A solution of sodium sulfate and water
D. A solution of copper(II) sulfate and water
Question 5
A solution containing 0.1 M NaOH is titrated with 0.1 M HCl. The pH of the solution at the equivalence point is 7. Calculate the pH of the solution at the half-equivalence point.
A. 3
B. 4
C. 5
D. 6
Question 6
A 2.0 g sample of a polymer is dissolved in 100 mL of solvent. The vis\cosity of the solution is 1.5 cP. Calculate the molar mass of the polymer.
A. 100 g/mol
B. 200 g/mol
C. 500 g/mol
D. 1000 g/mol
Question 7
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 8
The diagram below shows a titration setup. Identify the part labeled A.
A. Burette
B. Beaker
C. Test tube
D. Cylinder
Question 9
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 10
The reaction of an alkane with chlorine gas in the presence of light is a typical example of a reaction that proceeds via a radical mechanism. What is the major product formed when 2-methylpropane reacts with chlorine gas?
A. 1,1-dichloro-2-methylpropane
B. 1,2-dichloro-2-methylpropane
C. 2,2-dichloro-2-methylpropane
D. 2,3-dichloro-2-methylpropane
Question 11
A 2.5 M solution of HCl is prepared by dissolving 12.5 g of HCl in 500 mL of water. Calculate the concentration of the solution in units of mol/L.
A. 0.1 M
B. 0.5 M
C. 1.0 M
D. 2.0 M
Question 12
A solution containing 0.1 M HCl and 0.1 M NaOH is prepared. What is the pH of the solution after complete neutralization?
A. 1
B. 7
C. 10
D. 14
Question 13
A 0.1 M solution of NaCl is mixed with 10 mL of 0.1 M AgNO3. What is the concentration of AgCl formed?
A. 0.01 M
B. 0.1 M
C. 0.2 M
D. 0.5 M
Question 14
A colloidal solution of starch in water is 0.5% by mass. If the density of the solution is 1.0 g/mL, what is the concentration of the starch in g/L?
A. 0.5 g/L
B. 5.0 g/L
C. 50.0 g/L
D. 500.0 g/L
Question 15
Determine the s\tandard Gibbs free energy change \( ΔG^circ \) for the reaction: 2NO(g) + O2(g) → 2NO2(g) at 298 K and 1 atm, given that ΔH^circ = -114.2 kJ/mol and ΔS^circ = -146.4 J/mol*K.
A. -114.2 kJ/mol
B. -146.4 kJ/mol
C. -114.2 kJ/mol + 146.4 J/mol*K
D. -114.2 kJ/mol - 146.4 J/mol*K

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