POST UTME UNILAG 2023 Chemistry | Objective

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Question 1
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(Ca(s)) = -178.2 kJ/mol. Assume the reaction is Ca(s) + CO2(g) → CaCO3(s).
Correct A. -1207.7 kJ/mol
B. -1207.8 kJ/mol
C. -1207.9 kJ/mol
D. -1208.0 kJ/mol

Correct Answer: A

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Question 2
A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the pH of the solution after the addition of 25.0 mL of NaOH.
A. 2.00
Correct B. 2.50
C. 3.00
D. 3.50

Correct Answer: B

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Question 3
A diagram of a titration setup is shown below. If 25.0 mL of 0.100 M HCl is titrated with 0.100 M NaOH, what is the pH of the solution after the addition of 25.0 mL of NaOH?
A. 2.00
Correct B. 2.50
C. 3.00
D. 3.50

Correct Answer: B

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Question 4
A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the number of moles of HCl that react with NaOH.
Correct A. 0.0025 mol
B. 0.0026 mol
C. 0.0027 mol
D. 0.0028 mol

Correct Answer: A

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Question 5
A diagram of a titration setup is shown below. If 25.0 mL of 0.100 M HCl is titrated with 0.100 M NaOH, what is the number of moles of HCl that react with NaOH?
Correct A. 0.0025 mol
B. 0.0026 mol
C. 0.0027 mol
D. 0.0028 mol

Correct Answer: A

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Question 6
At 298 K, the s\tandard enthalpy change \( ΔH^circ \) for the reaction: 2NO(g) + O2(g) → 2NO2(g) is -114.1 kJ/mol. Calculate the s\tandard entropy change \( ΔS^circ \) for the reaction.
Correct A. -143.5 J/mol·K
B. -143.5 J/mol·K
C. -143.5 J/mol·K
D. -143.5 J/mol·K

Correct Answer: A

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Question 7
The s\tandard Gibbs free energy change \( ΔG^circ \) for the reaction: 2NO(g) + O2(g) → 2NO2(g) at 298 K is -114.1 kJ/mol. Calculate the equilibrium cons\tant (K) for the reaction.
Correct A. 1.1 × 10^5
B. 1.1 × 10^5
C. 1.1 × 10^5
D. 1.1 × 10^5

Correct Answer: A

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Question 8
The s\tandard enthalpy of formation \( ΔH_f^circ \) for NO(g) is 90.29 kJ/mol. The s\tandard enthalpy of formation \( ΔH_f^circ \) for O2(g) is 0 kJ/mol. Calculate the s\tandard enthalpy of formation \( ΔH_f^circ \) for NO2(g) u\sing Hess's law.
Correct A. 33.2 kJ/mol
B. 33.2 kJ/mol
C. 33.2 kJ/mol
D. 33.2 kJ/mol

Correct Answer: A

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Question 9
The s\tandard entropy change \( ΔS^circ \) for the reaction: 2NO(g) + O2(g) → 2NO2(g) is -143.5 J/mol·K. Calculate the s\tandard Gibbs free energy change \( ΔG^circ \) for the reaction at 298 K.
Correct A. -114.1 kJ/mol
B. -114.1 kJ/mol
C. -114.1 kJ/mol
D. -114.1 kJ/mol

Correct Answer: A

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Question 10
The s\tandard enthalpy of formation \( ΔH_f^circ \) for NO2(g) is 33.2 kJ/mol. The s\tandard enthalpy of formation \( ΔH_f^circ \) for O2(g) is 0 kJ/mol. Calculate the s\tandard enthalpy of formation \( ΔH_f^circ \) for NO(g) u\sing Hess's law.
Correct A. 90.29 kJ/mol
B. 90.29 kJ/mol
C. 90.29 kJ/mol
D. 90.29 kJ/mol

Correct Answer: A

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Question 11
Determine the pH of a 0.1 M solution of HCl.
A. 1
B. 2
C. 3
Correct D. 4

Correct Answer: D

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Question 12
Calculate the molar enthalpy of vaporization of a subs\tance that has a boiling point of 373 K and a molar heat capacity of 40 J/mol·K.
Correct A. -40 kJ/mol
B. -20 kJ/mol
C. -10 kJ/mol
D. 10 kJ/mol

Correct Answer: A

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Question 13
A 2.0 M solution of NaOH is titrated with a 1.0 M solution of HCl. What is the pH of the solution after 25 mL of HCl has been added?
A. 2
Correct B. 3
C. 4
D. 5

Correct Answer: B

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Question 14
A 1.0 M solution of H2SO4 is titrated with a 1.0 M solution of NaOH. What is the pH of the solution after 50 mL of NaOH has been added?
A. 1
B. 2
C. 3
Correct D. 4

Correct Answer: D

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Question 15
A 2.0 M solution of NaOH is titrated with a 1.0 M solution of HCl. What is the pH of the solution after 50 mL of HCl has been added?
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 16
A metal M has a crystal structure with a lattice parameter of 3.5 Å. If the metal has a density of 8.9 g/cm³, calculate the number of atoms per unit cell.
A. 4
Correct B. 6
C. 8
D. 10

Correct Answer: B

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Question 17
A solution of NaCl is prepared by dissolving 35.5 g of NaCl in 250 cm³ of water. Calculate the molarity of the solution.
A. 0.15 M
Correct B. 0.25 M
C. 0.35 M
D. 0.45 M

Correct Answer: B

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Question 18
A sample of CO2 gas occupies a volume of 2.5 dm³ at a pressure of 1.5 atm. Calculate the number of moles of CO2 present.
A. 0.05 mol
B. 0.10 mol
Correct C. 0.15 mol
D. 0.20 mol

Correct Answer: C

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Question 19
A solution of HCl is prepared by dissolving 25 g of HCl in 100 cm³ of water. Calculate the concentration of the solution in terms of molarity.
A. 1.0 M
Correct B. 2.0 M
C. 3.0 M
D. 4.0 M

Correct Answer: B

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Question 20
A sample of Fe2O3 is heated in a Bunsen burner flame. What is the color of the flame?
A. Green
B. Blue
Correct C. Red
D. Yellow

Correct Answer: C

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Question 21
At 25°C, 1.00 L of an ideal gas at 1.00 atm exerts a pressure of 101.3 kPa. What is the volume of the gas at 2.00 atm and 25°C?
A. 0.500 L
Correct B. 1.00 L
C. 2.00 L
D. 4.00 L

Correct Answer: B

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Question 22
A solution contains 25.0 g of NaCl. If 50.0 mL of 0.100 M HCl is added to the solution, what is the resulting pH?
A. 1.00
B. 2.00
C. 3.00
Correct D. 4.00

Correct Answer: D

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Question 23
A 0.100 M solution of NaOH is prepared by dissolving 4.00 g of NaOH in 1.00 L of water. What is the molarity of the solution?
Correct A. 0.100 M
B. 0.200 M
C. 0.300 M
D. 0.400 M

Correct Answer: A

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Question 24
A 1.00 L solution contains 0.100 g of KNO3. What is the molarity of the solution?
Correct A. 0.100 M
B. 0.200 M
C. 0.300 M
D. 0.400 M

Correct Answer: A

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Question 25
A 0.100 M solution of HCl is prepared by dissolving 4.00 g of HCl in 1.00 L of water. What is the molarity of the solution?
Correct A. 0.100 M
B. 0.200 M
C. 0.300 M
D. 0.400 M

Correct Answer: A

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