POST UTME NILE UNIVERSITY 2021 Chemistry | Objective

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Question 1
A sample of a gas at 25°C and 1 atm has a volume of 2.5 L. If the pressure is increased to 2 atm, what is the new volume of the gas?
A. 1.25 L
B. 1.5 L
C. 2.0 L
D. 2.5 L
Question 2
A reaction is represented by the equation: 2A + B → 2C + D. If 2.0 mol of A and 1.0 mol of B are present, what is the limiting reac\tant?
A. A
B. B
C. C
D. D
Question 3
A solution contains 0.1 M NaCl. What is the concentration of Cl- ions in the solution?
A. 0.05 M
B. 0.1 M
C. 0.15 M
D. 0.2 M
Question 4
A 25.0 g sample of a subs\tance is found to have a mass of 10.0 g after being burned in air. If the subs\tance is composed of 85.0% carbon and 15.0% hydrogen, calculate the energy released per gram of the subs\tance.
A. -3.5 kJ/g
B. -4.5 kJ/g
C. -5.5 kJ/g
D. -6.5 kJ/g
Question 5
Determine the s\tandard electrode potential of the cell represented by the following reaction: MnO4- + 8H+ + 5e- → Mn2+ + 4H2O. Given that the s\tandard electrode potential of the MnO4-/Mn2+ couple is +1.23 V.
A. +1.23 V
B. +1.46 V
C. +1.69 V
D. +1.92 V
Question 6
A 1.00 M solution of sodium chloride (NaCl) is mixed with a 1.00 M solution of hydrochloric acid (HCl). Calculate the concentration of the resulting solution.
A. 0.25 M
B. 0.50 M
C. 0.75 M
D. 1.00 M
Question 7
A sample of nitrogen gas is collected over water at a temperature of 25°C and a pressure of 1.0 atm. If the vapor pressure of water at 25°C is 0.0313 atm, what is the partial pressure of nitrogen gas?
A. 0.9687 atm
B. 0.9697 atm
C. 0.9707 atm
D. 0.9717 atm
Question 8
A sample of a metal (M) reacts with oxygen gas to form a metal oxide (MO). If 2.5 g of the metal is burned in air, and the volume of oxygen gas consumed is 1.2 L at 25°C and 1 atm, calculate the molar mass of the metal.
A. 50 g/mol
B. 60 g/mol
C. 70 g/mol
D. 80 g/mol
Question 9
A 2.50 M solution of sulfuric acid (H2SO4) is mixed with a 1.25 M solution of sodium hydroxide (NaOH). Calculate the number of moles of sulfuric acid that react with sodium hydroxide to form water and sodium sulfate.
A. 0.5 mol
B. 1.0 mol
C. 1.5 mol
D. 2.0 mol
Question 10
A 0.5 M solution of sodium hydroxide is mixed with a 0.5 M solution of hydrochloric acid. What is the pH of the resulting solution?
A. 7
B. 8
C. 9
D. 10
Question 11
A sample of a gas at 25°C and 1 atm is found to have a volume of 2.5 L. What is the number of moles of the gas?
A. 0.1
B. 0.2
C. 0.3
D. 0.4
Question 12
A 2.0 L container is filled with 1.5 mol of an ideal gas at 27°C. Calculate the pressure of the gas u\sing the ideal gas law.
A. 2.5 atm
B. 3.0 atm
C. 3.5 atm
D. 4.0 atm
Question 13
A solution of sodium chloride is electrolyzed u\sing a platinum electrode. The reaction at the cathode is:
A. 2Na+(aq) + 2e- → Na(s)
B. 2Cl-(aq) + 2e- → Cl2(g)
C. 2Na+(aq) + 2e- → Na2(g)
D. 2Cl-(aq) + 2e- → Cl2(s)
Question 14
The s\tandard enthalpy of formation of CO2 is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of CO?
A. -110.5 kJ/mol
B. -210.5 kJ/mol
C. -310.5 kJ/mol
D. -410.5 kJ/mol
Question 15
The reaction of nitrogen with oxygen to form nitrogen dioxide is an example of a redox reaction. Write the balanced chemical equation for this reaction, including the s\tandard enthalpy change (ΔH°) and the s\tandard entropy change (ΔS°).
A. 2NO + O2 → 2NO2, ΔH° = -114.2 kJ/mol, ΔS° = -146.4 J/mol K
B. 2NO2 + O2 → 2NO, ΔH° = 114.2 kJ/mol, ΔS° = 146.4 J/mol K
C. 2NO + O2 → 2NO2, ΔH° = 114.2 kJ/mol, ΔS° = 146.4 J/mol K
D. 2NO2 + O2 → 2NO, ΔH° = -114.2 kJ/mol, ΔS° = -146.4 J/mol K

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