POST UTME PAN-ATLANTIC UNIVERSITY 2020 Chemistry | Objective

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Question 1
A 2.5 L flask contains 0.15 mol of an ideal gas at 27°C. Calculate the pressure of the gas u\sing the ideal gas law.
A. 2.1 atm
B. 2.2 atm
C. 2.3 atm
D. 2.4 atm
Question 2
A 2.50 g sample of a polymer is dissolved in 25.0 mL of a solvent. If the molar mass of the polymer is 50.0 g/mol, calculate the concentration of the polymer solution.
A. 0.100 M
B. 0.125 M
C. 0.150 M
D. 0.175 M
Question 3
A 2.5 L sample of a gas at 27°C and 1 atm is collected over water. If the vapor pressure of water at 27°C is 0.0313 atm, calculate the partial pressure of the gas.
A. 0.969 atm
B. 0.98 atm
C. 0.991 atm
D. 1 atm
Question 4
A sample of O2 gas is collected over water at 25°C and 1 atm. If the partial pressure of O2 is 0.50 atm, calculate the mole \fraction of O2 in the gas mixture.
A. 0.25
B. 0.50
C. 0.75
D. 1.00
Question 5
A 2.5 M solution of HCl is titrated with 1.0 M NaOH. Calculate 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 6
A polymer is a large molecule composed of many repeated subunits called monomers. Which of the following is a characteristic of polymers?
A. They are typically small molecules
B. They have a high melting point
C. They are composed of many repeated subunits called monomers
D. They are typically soluble in water
Question 7
A solution of 0.100 M HCl is titrated with 0.100 M NaOH. If 25.0 mL of HCl is required to reach the equivalence point, what is the concentration of the resulting solution?
A. 0.050 M
B. 0.075 M
C. 0.100 M
D. 0.125 M
Question 8
A 1.0 M solution of NaOH is titrated with 1.0 M HCl. Calculate the pH of the solution after 50 mL of HCl has been added.
A. 1.0
B. 2.0
C. 3.0
D. 4.0
Question 9
A polymer has a molecular weight of 100,000 g/mol and a degree of polymerization of 500. What is its molar mass?
A. 500 g/mol
B. 1000 g/mol
C. 2000 g/mol
D. 5000 g/mol
Question 10
A 2.50 g sample of a polymer is dissolved in 25.0 mL of a solvent. If the molar mass of the polymer is 50.0 g/mol, calculate the number of moles of polymer dissolved.
A. 0.0500 mol
B. 0.0505 mol
C. 0.0510 mol
D. 0.0515 mol
Question 11
A 2.0 g sample of a hydrocarbon is burned in a bomb calorimeter. The temperature of the calorimeter increases by 3.5°C. Calculate the heat of combustion of the hydrocarbon.
A. -3600 kJ/mol
B. -3700 kJ/mol
C. -3800 kJ/mol
D. -3900 kJ/mol
Question 12
The half-life of a radioactive subs\tance is 5 days. If 100 mg of the subs\tance is initially present, how much will remain after 20 days?
A. 12.5 mg
B. 25 mg
C. 50 mg
D. 100 mg
Question 13
Determine the s\tandard enthalpy of formation of CaCO3(s) from the following data: ΔHf(CaO(s)) = -635.09 kJ/mol, ΔHf(CO2(g)) = -393.51 kJ/mol, ΔHf(C(s)) = 0 kJ/mol.
A. -1785.6 kJ/mol
B. -1785.9 kJ/mol
C. -1786.1 kJ/mol
D. -1786.3 kJ/mol
Question 14
The diagram below shows a titration setup. Identify the part labeled A.
A. Burette
B. Conical flask
C. Pipette
D. Thermometer
Question 15
A 2.50 g sample of an unknown hydrocarbon is burned in a combustion calorimeter. The resulting CO2 gas is collected and found to have a volume of 1.25 L at 25°C and 1 atm. What is the empirical formula of the hydrocarbon?
A. C2H6
B. C3H8
C. C4H10
D. C5H12

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