POST UTME UNN 2025 Chemistry | Objective

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Question 1
A sample of air is collected over water and has a volume of 2.0 L at 25°C and 1 atm. If the partial pressure of water vapor is 0.04 atm, what is the mole \fraction of water vapor in the air?
A. 0.02
B. 0.04
C. 0.06
D. 0.08
Question 2
A 2 L solution of 0.2 M H2SO4 is prepared by dissolving 40 g of H2SO4 in water. What is the concentration of the solution in moles per liter?
A. 0.2 M
B. 0.4 M
C. 0.6 M
D. 0.8 M
Question 3
A sample of air is collected over water and has a volume of 1.5 L at 25°C and 1 atm. If the partial pressure of water vapor is 0.03 atm, what is the mole \fraction of water vapor in the air?
A. 0.02
B. 0.04
C. 0.06
D. 0.08
Question 4
A sample of a metal oxide has a mass of 25 g and a volume of 2.5 cm3. What is the density of the metal oxide?
A. \( 10 , \text{g/cm}^3 \)
B. \( 20 , \text{g/cm}^3 \)
C. \( 30 , \text{g/cm}^3 \)
D. \( 40 , \text{g/cm}^3 \)
Question 5
A 1.00 L sample of a gas at 25°C and 1.00 atm is collected over water at 25°C. If the vapor pressure of water at 25°C is 23.8 mmHg, what is the partial pressure of the gas?
A. 0.76 atm
B. 0.86 atm
C. 0.96 atm
D. 1.06 atm
Question 6
Determine the s\tandard enthalpy of formation of CaCO3(s) from the following data:\n\nΔHf(CaO(s)) = -635.09 kJ/mol\nΔHf(CO2(g)) = -393.51 kJ/mol\nΔHf(Ca(s)) = -178.2 kJ/mol
A. -1206.79 kJ/mol
B. -1206.79 kJ/mol
C. -1206.79 kJ/mol
D. -1206.79 kJ/mol
Question 7
A diagram of a titration setup is shown below. If 25.0 mL of 0.1 M NaOH is required to reach the equivalence point, what is the concentration of the HCl solution?
A. 0.05 M
B. 0.1 M
C. 0.2 M
D. 0.5 M
Question 8
A 10.0 g sample of a compound containing only C, H, and O is analyzed by combustion and found to produce 11.0 g of CO2 and 5.0 g of H2O. What is the empirical formula of the compound?
A. C2H4O
B. C2H4O
C. C2H4O
D. C2H4O
Question 9
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. -130.5 kJ/mol
C. -150.5 kJ/mol
D. -170.5 kJ/mol
Question 10
Determine the molar mass of a gas that occupies 2.5 L at 27°C and 1.2 atm. Use the ideal gas law to calculate the number of moles.
A. \( 2.5 , \text{L} \times 1.2 , \text{atm} \times 0.0821 , \text{L atm/mol K} \times 300 , \text{K} \)
B. \( 2.5 , \text{L} \times 1.2 , \text{atm} \times 0.0821 , \text{L atm/mol K} \times 300 , \text{K} \times 6.022 \times 10^{23} \)
C. \( 2.5 , \text{L} \times 1.2 , \text{atm} \times 0.0821 , \text{L atm/mol K} \times 300 , \text{K} \times 6.022 \times 10^{23} \times 4.184 , \text{J/g°C} \)
D. \( 2.5 , \text{L} \times 1.2 , \text{atm} \times 0.0821 , \text{L atm/mol K} \times 300 , \text{K} \times 6.022 \times 10^{23} \times 4.184 , \text{J/g°C} \times 10^{-3} , \text{kg/g} \)
Question 11
A metal alloy consists of 75% copper and 25% zinc. If 2.5 kg of the alloy is melted and cast into a cylindrical shape, what is the volume of the cylinder?
A. \( 2.5 , \text{kg} \times 0.75 \times 8.9 , \text{g/cm}^3 \)
B. \( 2.5 , \text{kg} \times 0.75 \times 8.9 , \text{g/cm}^3 \times 1000 , \text{cm}^3/\text{L} \)
C. \( 2.5 , \text{kg} \times 0.75 \times 8.9 , \text{g/cm}^3 \times 1000 , \text{cm}^3/\text{L} \times pi , \text{r}^2 \)
D. \( 2.5 , \text{kg} \times 0.75 \times 8.9 , \text{g/cm}^3 \times 1000 , \text{cm}^3/\text{L} \times pi , \text{r}^2 \times 2 , \text{cm} \)
Question 12
A 1.0 M solution of NaOH is titrated with a 1.0 M solution of HCl. If 25 mL of HCl is required to reach the equivalence point, what is the volume of NaOH required to reach the equivalence point?
A. 25
B. 50
C. 75
D. 100
Question 13
A 1.0 g sample of sulfur is burned in a bomb calorimeter and releases 2000 J of heat. If the heat of combustion of sulfur is 1000 J/g, what is the percentage yield of sulfur?
A. 50
B. 60
C. 70
D. 80
Question 14
A 1.0 g sample of sulfur is burned in a bomb calorimeter and releases 1000 J of heat. If the heat of combustion of sulfur is 1000 J/g, what is the percentage yield of sulfur?
A. 50
B. 60
C. 70
D. 80
Question 15
A 1.0 M solution of NaOH is titrated with a 1.0 M solution of HCl. If 25 mL of HCl is required to reach the equivalence point, what is the volume of NaOH required to reach the equivalence point?
A. 25
B. 50
C. 75
D. 100

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