POST UTME UNIBEN 2018 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
What is the pH of a 0.10 M solution of HCl?
A. 0.10
B. 1.0
C. 2.0
D. 3.0
Question 2
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
B. 1.000
C. 1.500
D. 2.000
Question 3
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
B. XCl_2
C. XCl_3
D. XCl_4
Question 4
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
C. 0.150 M
D. 0.200 M
Question 5
A 2.0 g sample of a metal oxide is heated in a crucible until it is completely reduced to the metal. If the mass of the metal produced is 1.5 g, what is the percentage yield of the reaction?
A. 50%
B. 60%
C. 70%
D. 80%
Question 6
The pH of a solution is 4.5. What is the concentration of hydrogen ions \( H+ \) in the solution?
A. 1.0 x 10^\( -4 \) M
B. 1.0 x 10^\( -5 \) M
C. 1.0 x 10^\( -6 \) M
D. 1.0 x 10^\( -7 \) M
Question 7
The reaction of cyclohexane with bromine in the presence of light is an example of a ______________ reaction.
A. substitution reaction
B. elimination reaction
C. addition reaction
D. oxidation reaction
Question 8
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
C. 0.4 M
D. 0.5 M
Question 9
A 2.0 M solution of sodium hydroxide (NaOH) is titrated with a 1.0 M solution of hydrochloric acid (HCl). What is the pH of the solution after the titration?
A. 7.0
B. 8.0
C. 9.0
D. 10.0
Question 10
A 1.0 M solution of potassium permanganate (KMnO4) is electrolyzed u\sing a platinum electrode. What is the concentration of manganese dioxide (MnO2) formed at the cathode?
A. 0.5 M
B. 1.0 M
C. 2.0 M
D. 3.0 M
Question 11
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
B. +1.48 V
C. +1.93 V
D. +2.18 V
Question 12
Determine the molar mass of a gas that occupies 2.5 L at 27°C and 1.0 atm.
A. 20 g/mol
B. 30 g/mol
C. 40 g/mol
D. 50 g/mol
Question 13
A 0.1 M solution of a weak acid HA is titrated with 0.1 M NaOH. If the initial pH of the acid is 4.5, what is the pH of the solution after the addition of 20 mL of NaOH?
A. \( pH = 7 \)
B. \( pH = 8 \)
C. \( pH = 9 \)
D. \( pH = 10 \)
Question 14
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
C. 3.5 L
D. 4.5 L
Question 15
A 1.0 M solution of a weak base B is titrated with 1.0 M HCl. If the initial pH of the base is 9.5, what is the pH of the solution after the addition of 20 mL of HCl?
A. \( pH = 6 \)
B. \( pH = 7 \)
C. \( pH = 8 \)
D. \( pH = 9 \)

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