POST UTME CRAWFORD UNIVERSITY 2024 Chemistry | Objective

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Question 1
Determine the s\tandard enthalpy of formation of NO2(g) from the following data: ΔHf(N2(g)) = 0 kJ/mol, ΔHf(O2(g)) = 0 kJ/mol, ΔHf(NO(g)) = 91.3 kJ/mol. The reaction is: N2(g) + 2O2(g) → 2NO2(g).
Correct A. -339.9 kJ/mol
B. -339.8 kJ/mol
C. -339.7 kJ/mol
D. -339.6 kJ/mol

Correct Answer: A

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Question 2
A solution containing 0.1 M NH3(aq) is mixed with 0.1 M HCl(aq). If the reaction is: NH3(aq) + HCl(aq) → NH4Cl(aq), what is the concentration of NH3(aq) after the reaction is complete?
A. 0 M
B. 0.1 M
Correct C. 0.05 M
D. 0.01 M

Correct Answer: C

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Question 3
The half-life of a radioactive subs\tance is 5 years. If 100 g of the subs\tance is present initially, what mass of the subs\tance will remain after 10 years?
A. 50 g
B. 25 g
Correct C. 12.5 g
D. 6.25 g

Correct Answer: C

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Question 4
A sample of CO2(g) is collected over water at 25°C and 1 atm. If the partial pressure of CO2(g) is 0.8 atm, what is the mole \fraction of CO2(g) in the gas mixture?
Correct A. 0.8
B. 0.7
C. 0.6
D. 0.5

Correct Answer: A

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Question 5
A 2.0 M solution of NaOH(aq) is mixed with 1.0 M HCl(aq). If the reaction is: NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l), what is the concentration of NaOH(aq) after the reaction is complete?
A. 1.0 M
Correct B. 0.5 M
C. 0.25 M
D. 0.1 M

Correct Answer: B

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Question 6
A 2.5 M solution of NaOH is prepared by dissolving 12.5 g of NaOH in water to make 250 mL of solution. Calculate the molarity of the solution.
Correct A. 2.5 M
B. 3.0 M
C. 2.0 M
D. 1.5 M

Correct Answer: A

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Question 7
The s\tandard Gibbs free energy change for the reaction 2Ag+ + Cu → 2Ag + Cu2+ is -120 kJ/mol. Calculate the equilibrium cons\tant (K) for the reaction.
A. 10^\( -6 \)
Correct B. 10^\( -12 \)
C. 10^\( -18 \)
D. 10^\( -24 \)

Correct Answer: B

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Question 8
A 1.0 L solution of 0.1 M HCl is mixed with 1.0 L of 0.1 M NaOH. What is the pH of the resulting solution?
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 9
The reaction 2NO(g) + O2(g) → 2NO2(g) has a s\tandard enthalpy change of -114 kJ/mol. Calculate the s\tandard entropy change (ΔS) for the reaction.
Correct A. -120 J/mol·K
B. -140 J/mol·K
C. -160 J/mol·K
D. -180 J/mol·K

Correct Answer: A

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Question 10
A 1.0 L solution of 0.1 M HCl is mixed with 1.0 L of 0.1 M NaOH. What is the concentration of the resulting solution?
A. 0.1 M
Correct B. 0.05 M
C. 0.01 M
D. 0.005 M

Correct Answer: B

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Question 11
A solution of potassium permanganate (KMnO4) is titrated with a solution of sodium oxalate (Na2C2O4). The reaction is as follows: 2KMnO4 + 5Na2C2O4 + H2SO4 → K2SO4 + 2MnSO4 + 10NaC2O4 + 2H2O. If 25.0 cm3 of 0.1 mol dm-3 KMnO4 is required to react with 20.0 cm3 of 0.2 mol dm-3 Na2C2O4, calculate the number of moles of Na2C2O4 present in the solution.
Correct A. 0.05 mol
B. 0.1 mol
C. 0.2 mol
D. 0.5 mol

Correct Answer: A

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Question 12
A 2.5 g sample of a metal carbonate is heated to produce a metal oxide and carbon dioxide gas. The mass of the metal oxide produced is 1.5 g. Calculate the mass of carbon dioxide gas produced.
A. 0.5 g
B. 1.0 g
Correct C. 1.5 g
D. 2.0 g

Correct Answer: C

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Question 13
A solution of sodium hydroxide (NaOH) is titrated with a solution of hydrochloric acid (HCl). The reaction is as follows: NaOH + HCl → NaCl + H2O. If 20.0 cm3 of 0.1 mol dm-3 NaOH is required to react with 30.0 cm3 of 0.2 mol dm-3 HCl, calculate the number of moles of HCl present in the solution.
A. 0.05 mol
Correct B. 0.1 mol
C. 0.2 mol
D. 0.5 mol

Correct Answer: B

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Question 14
A 2.0 g sample of a metal hydroxide is heated to produce a metal oxide and water vapor. The mass of the metal oxide produced is 1.5 g. Calculate the mass of water vapor produced.
A. 0.5 g
B. 1.0 g
Correct C. 1.5 g
D. 2.0 g

Correct Answer: C

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Question 15
A solution of potassium chloride (KCl) is titrated with a solution of silver nitrate (AgNO3). The reaction is as follows: 2KCl + AgNO3 → AgCl + KNO3. If 25.0 cm3 of 0.1 mol dm-3 KCl is required to react with 20.0 cm3 of 0.2 mol dm-3 AgNO3, calculate the number of moles of AgNO3 present in the solution.
A. 0.05 mol
Correct B. 0.1 mol
C. 0.2 mol
D. 0.5 mol

Correct Answer: B

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