POST UTME CHRISTOPHER UNIVERSITY 2021 Chemistry | Objective

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Question 1
A 0.500 g sample of a metal is heated in a crucible to produce 0.350 g of the metal. If the metal has a molar mass of 40.0 g/mol, calculate the percentage yield of the metal.
A. 70.0%
B. 75.0%
C. 80.0%
D. 85.0%
Question 2
The s\tandard enthalpy of formation of CO2(g) is -393.51 kJ/mol. What is the s\tandard enthalpy of formation of CO(g)?
A. -110.5 kJ/mol
B. -110.5 kJ/mol
C. -110.5 kJ/mol
D. -110.5 kJ/mol
Question 3
A solution contains 0.0500 M FeCl3 and 0.0500 M NaOH. What is the concentration of Fe(OH)3 formed after the reaction is complete?
A. 0.0500 M
B. 0.100 M
C. 0.150 M
D. 0.200 M
Question 4
A 10 mL sample of a solution containing a mixture of NaCl and Na2SO4 is electrolyzed u\sing a current of 2 A for 5 minutes. If the initial concentration of Na+ ions is 0.1 M, what is the concentration of Na+ ions after electrolysis?
A. 0.05 M
B. 0.1 M
C. 0.15 M
D. 0.2 M
Question 5
A 0.1 M solution of HCl is mixed with a 0.2 M solution of NaOH. What is the pH of the resulting solution?
A. 1
B. 2
C. 3
D. 4
Question 6
A 10 mL sample of a solution containing a mixture of NaCl and Na2SO4 is electrolyzed u\sing a current of 2 A for 5 minutes. If the initial concentration of Na+ ions is 0.1 M, what is the concentration of Na+ ions after electrolysis?
A. 0.05 M
B. 0.1 M
C. 0.15 M
D. 0.2 M
Question 7
A 2.50-g sample of a metal (M) is dissolved in 50.0 mL of 0.100 M HCl. The resulting solution is then titrated with 0.0500 M NaOH. If 25.0 mL of NaOH is required to reach the equivalence point, what is the identity of the metal M?
A. Zn
B. Fe
C. Cu
D. Ag
Question 8
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 3.5, what is the pH after the addition of 20 mL of NaOH?
A. 4.5
B. 5.5
C. 6.5
D. 7.5
Question 9
Determine the molar solubility of Ag2CrO4 in 0.1 M NaCl solution, given that the solubility product cons\tant (Ksp) for Ag2CrO4 is 1.1 × 10^-12.
A. 1.0 × 10^-5 M
B. 1.5 × 10^-5 M
C. 2.0 × 10^-5 M
D. 3.0 × 10^-5 M
Question 10
The reaction of 1.00 g of an unknown hydrocarbon \( C_xH_y \) with 50.0 mL of 0.100 M KMnO4 in acidic solution results in the oxidation of the hydrocarbon. If 25.0 mL of 0.0500 M NaOH is required to reach the equivalence point, what is the empirical formula of the hydrocarbon?
A. C2H4
B. C3H6
C. C4H8
D. C5H10
Question 11
A 1.0 M solution of NaOH is titrated with a 2.0 M solution of HCl. If 25 mL of HCl is required to reach the equivalence point, what is the number of moles of NaOH in the original solution?
A. 0.125 moles
B. 0.25 moles
C. 0.5 moles
D. 1.0 moles
Question 12
Determine the pH of a 0.1 M solution of HCl at 25°C. The dissociation cons\tant of HCl is 10^\( -7 \).
A. 1
B. 2
C. 3
D. 4
Question 13
A sample of a gas has a volume of 2.5 L at a pressure of 1.5 atm and a temperature of 298 K. What is the volume of the gas at a pressure of 3.0 atm and a temperature of 323 K?
A. 3.2 L
B. 3.2 L
C. 3.2 L
D. 3.2 L
Question 14
A solution contains 0.1 mol of NaCl and 0.2 mol of CaCl2. What is the total number of moles of ions present in the solution?
A. 0.3
B. 0.5
C. 0.7
D. 0.9
Question 15
A 1.00 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 torr, what is the partial pressure of the gas?
A. 1.00 atm
B. 0.980 atm
C. 1.02 atm
D. 1.05 atm

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