POST UTME WELLSPRING UNIVERSITY 2017 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
The half-life of a radioactive subs\tance is 5 years. If the initial amount of the subs\tance is 100 g, calculate the amount remaining after 10 years.
A. 50
B. 75
C. 87.5
D. 100
Question 2
Determine the molar mass of a polymer with the following molecular formula: [CH2CH2]n. Assume that the polymer is composed of only carbon and hydrogen atoms.
A. 12 g/mol
B. 24 g/mol
C. 36 g/mol
D. 48 g/mol
Question 3
A 0.1 M solution of a weak acid HA is mixed with a 0.2 M solution of a strong base NaOH. The resulting solution is 0.1 M in HA and 0.2 M in NaOH. Calculate the concentration of the conjugate base A^-.
A. \( [A^-] = 0.1 , M \)
B. \( [A^-] = 0.2 , M \)
C. \( [A^-] = 0.3 , M \)
D. \( [A^-] = 0.4 , M \)
Question 4
A mixture of 1.00 g of sodium chloride (NaCl) and 1.00 g of glu\cose (C6H12O6) is dissolved in 100.0 mL of water. Calculate the molar concentration of each solute in the solution.
A. 0.0171 M
B. 0.0342 M
C. 0.0513 M
D. 0.0684 M
Question 5
A 5.00 g sample of a metal carbonate is heated to produce a 2.50 g sample of the metal oxide. What is the percentage of carbon dioxide produced during the heating process?
A. 40.0%
B. 45.0%
C. 50.0%
D. 55.0%
Question 6
A 100.0 mL sample of a solution containing 0.100 M NaCl is titrated with 0.100 M AgNO3. What is the pH of the resulting solution?
A. 1.00
B. 2.00
C. 3.00
D. 4.00
Question 7
A solution contains 0.1 M HCl and 0.1 M NaOH. What is the pH of the solution?
A. 1
B. 2
C. 3
D. 4
Question 8
A 10 g sample of a subs\tance is found to have a mass of 12 g when heated to 100°C. What is the molar enthalpy of vaporization of the subs\tance?
A. 40 kJ/mol
B. 50 kJ/mol
C. 60 kJ/mol
D. 70 kJ/mol
Question 9
What is the periodic tr\end for atomic radius in the periodic table?
A. Increases down a group
B. Decreases down a group
C. Increases across a period
D. Decreases across a period
Question 10
A 10.0 g sample of a metal hydroxide is dissolved in water to produce a 5.00 g sample of the metal chloride. What is the percentage of water in the resulting solution?
A. 30.0%
B. 35.0%
C. 40.0%
D. 45.0%
Question 11
What is the formula for the compound formed by the reaction of nitrogen and oxygen?
A. NO
B. N2O
C. NO2
D. N2O3
Question 12
A metal M reacts with HCl to form a salt and releases 1.5 moles of H2 gas per mole of M. The reaction is as follows: M + 2HCl -> MHCl2 + H2. Calculate the number of moles of M required to produce 3 moles of H2 gas.
A. 2
B. 3
C. 4
D. 5
Question 13
A 2.5 L flask contains 0.5 mol of an ideal gas at 27°C. What is the pressure of the gas?
A. 1.5 atm
B. 2.5 atm
C. 3.5 atm
D. 4.5 atm
Question 14
A solution contains 0.1 M NaCl and 0.2 M KNO3. What is the concentration of Cl^- ions in the solution?
A. 0.1 M
B. 0.2 M
C. 0.3 M
D. 0.4 M
Question 15
A 0.1 M solution of a weak acid HA is mixed with a 0.2 M solution of a strong base NaOH. The resulting solution is 0.1 M in HA and 0.2 M in NaOH. Calculate the concentration of the conjugate base A^-.
A. \( [A^-] = 0.1 , M \)
B. \( [A^-] = 0.2 , M \)
C. \( [A^-] = 0.3 , M \)
D. \( [A^-] = 0.4 , M \)

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