POST UTME OAU 2023 Chemistry | Objective

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Question 1
A solution of NaOH is prepared by dissolving 25 g of NaOH in 250 mL of water. What is the concentration of the solution in molarity?
A. 0.1 M
B. 0.2 M
C. 0.3 M
D. 0.4 M
Question 2
The reaction of zinc metal with copper(II) sulfate solution is represented by the equation: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s). What is the oxidation state of copper in the product Cu(s)?
A. 0
B. +1
C. +2
D. -1
Question 3
A sample of nitrogen gas is collected over water at 25°C and 1 atm. If the partial pressure of water vapor is 0.02 atm, what is the mole \fraction of nitrogen gas?
A. 0.98
B. 0.99
C. 0.995
D. 0.998
Question 4
The diagram below shows a titration setup. If 25 mL of 0.1 M HCl is added to the burette, what is the concentration of the NaOH solution?
A. 0.05 M
B. 0.1 M
C. 0.2 M
D. 0.5 M
Question 5
A 25 mL sample of 0.5 M H2SO4 is titrated with 1 M NaOH. Calculate the number of moles of NaOH required to reach the equivalence point.
A. 0.05
B. 0.1
C. 0.15
D. 0.2
Question 6
The atomic radius of an element is 100 pm. If the element is in its ground state, what is the energy of the electron in the n = 3 orbital?
A. -13.6 eV
B. -12.1 eV
C. -11.6 eV
D. -10.1 eV
Question 7
Determine the number of moles of oxygen gas (O2) produced at STP when 2.5 moles of hydrogen gas (H2) react with oxygen gas according to the equation: 2H2 + O2 → 2H2O.
A. 1.25 moles
B. 2.5 moles
C. 3.75 moles
D. 5 moles
Question 8
What is the major product of the reaction between 2-methylpropane and chlorine?
A. 1-chloro-2-methylpropane
B. 2-chloro-2-methylpropane
C. 1,1-dichloro-2-methylpropane
D. 1-chloro-1-methylpropane
Question 9
A 0.5 M solution of sodium hydroxide (NaOH) is mixed with a 0.5 M solution of hydrochloric acid (HCl). What is the pH of the resulting solution?
A. 1
B. 2
C. 7
D. 14
Question 10
The pH of a solution is 4.50. What is the concentration of hydrogen ions in the solution?
A. 1.00 × 10^-5 M
B. 1.00 × 10^-4 M
C. 1.00 × 10^-3 M
D. 1.00 × 10^-2 M
Question 11
A solution of NaOH is prepared by dissolving 30 g of NaOH in 300 mL of water. What is the concentration of the solution in molarity?
A. 0.1 M
B. 0.2 M
C. 0.3 M
D. 0.4 M
Question 12
A 0.1 M solution of HCl is titrated with 0.1 M NaOH. What is the pH of the solution after 25 mL of NaOH has been added?
A. 1.0
B. 2.0
C. 3.0
D. 4.0
Question 13
A 2.50 L flask contains 0.500 mol of an ideal gas at 298 K. What is the pressure of the gas in the flask?
A. 1.01 × 10^5 Pa
B. 2.02 × 10^5 Pa
C. 3.03 × 10^5 Pa
D. 4.04 × 10^5 Pa
Question 14
A 2.5 g sample of a non-metallic oxide is heated in a stream of hydrogen gas. If 1.8 g of water is collected, what is the empirical formula of the oxide?
A. MgO
B. CaO
C. SiO2
D. Al2O3
Question 15
The rate cons\tant (k) of a first-order reaction is 0.05 min^-1. If the initial concentration of the reac\tant is 0.1 M, what is the concentration after 10 minutes?
A. 0.005 M
B. 0.01 M
C. 0.02 M
D. 0.03 M

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