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POST UTME AAUA 2021 Chemistry | Objective

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Question 1 View Details

Calculate the s\tandard enthalpy change (ΔH°) for the reaction: 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s) given that the s\tandard enthalpy of formation (ΔHf°) for Al2O3(s) is -1675.7 kJ/mol, Al(s) is -1269.6 kJ/mol, Fe2O3(s) is -826.4 kJ/mol, and Fe(s) is 0 kJ/mol.

Correct A. -1340.6 kJ/mol

B. -1340.7 kJ/mol

C. -1340.8 kJ/mol

D. -1340.9 kJ/mol

Correct Answer: A

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Question 2 View Details

A 0.5 M solution of NaOH is prepared by dissolving 25 g of NaOH in 1 L of water. Calculate the molarity of the solution if 25 g of NaOH is dissolved in 1 L of water.

A. 0.5 M

Correct B. 0.25 M

C. 1.0 M

D. 1.5 M

Correct Answer: B

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Question 3 View Details

The diagram below shows the titration of 25 mL of 0.1 M HCl with 0.1 M NaOH. If the initial pH of the solution is 2.0, what is the pH of the solution after the addition of 25 mL of 0.1 M NaOH?

A. 3.0

B. 4.0

C. 5.0

Correct D. 6.0

Correct Answer: D

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Question 4 View Details

The s\tandard Gibbs free energy change (ΔG°) for the reaction: 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s) is -1340.6 kJ/mol. Calculate the equilibrium cons\tant (K) for the reaction.

Correct A. 10^\( -1340.6 \)

B. 10^\( -1340.7 \)

C. 10^\( -1340.8 \)

D. 10^\( -1340.9 \)

Correct Answer: A

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Question 5 View Details

The diagram below shows the structure of a hydrocarbon molecule. Identify the type of hydrocarbon.

A. Alkane

Correct B. Alkene

C. Alkyne

D. Aromatic

Correct Answer: B

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Question 6 View Details

Determine the number of moles of oxygen gas (O2) produced at s\tandard temperature and pressure (STP) when 2.5 moles of carbon monoxide (CO) react with excess oxygen according to the equation: 2CO + O2 → 2CO2.

Correct A. 1.25

B. 2.5

C. 5.0

D. 7.5

Correct Answer: A

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Question 7 View Details

A 25.0 mL sample of 0.100 M NaOH is titrated with 0.0500 M HCl. Calculate the number of moles of HCl required to reach the equivalence point.

A. 0.00250

Correct B. 0.00500

C. 0.00750

D. 0.0100

Correct Answer: B

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Question 8 View Details

A solution containing 0.500 M CaCl2 is mixed with a solution containing 0.750 M Na2SO4. Calculate the concentration of the resulting solution.

A. 0.375

B. 0.500

Correct C. 0.625

D. 0.750

Correct Answer: C

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Question 9 View Details

A 1.00 L sample of 0.100 M HCl is mixed with a 1.00 L sample of 0.100 M NaOH. Calculate the pH of the resulting solution.

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 10 View Details

A 25.0 mL sample of 0.100 M NaOH is titrated with 0.0500 M HCl. Calculate the volume of HCl required to reach the equivalence point.

A. 50.0

Correct B. 75.0

C. 100

D. 125

Correct Answer: B

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Question 11 View Details

The rate cons\tant of a first-order reaction is 0.05 min^-1. Calculate the half-life of the reaction.

Correct A. 10 min

B. 20 min

C. 30 min

D. 40 min

Correct Answer: A

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Question 12 View Details

A 0.1 M solution of HCl is titrated with 0.1 M NaOH. Calculate the pH of the solution after 20 mL of NaOH has been added.

A. 2

B. 3

Correct C. 4

D. 5

Correct Answer: C

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Question 13 View Details

A sample of water contains 10 ppm of Cl^- ions. Calculate the concentration of Cl^- ions in mg/L.

A. 1 mg/L

Correct B. 10 mg/L

C. 100 mg/L

D. 1000 mg/L

Correct Answer: B

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Question 14 View Details

A solution contains 0.1 M H2SO4 and 0.1 M NaOH. Calculate the pH of the solution.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 15 View Details

A 10 L solution of 0.1 M HCl is mixed with 10 L of 0.1 M NaOH. Calculate the pH of the resulting solution.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 16 View Details

A mixture of 2.50 g of sodium chloride (NaCl) and 1.50 g of calcium chloride (CaCl2) is dissolved in 100.0 mL of water. Calculate the molar concentration of the resulting solution.

A. 0.050 M

B. 0.075 M

Correct C. 0.100 M

D. 0.125 M

Correct Answer: C

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Question 17 View Details

A sample of a polymer has a molecular weight of 50,000 g/mol. If 2.00 g of the polymer is dissolved in 100.0 mL of solvent, what is the concentration of the solution in g/L?

A. 20.0 g/L

Correct B. 25.0 g/L

C. 30.0 g/L

D. 35.0 g/L

Correct Answer: B

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Question 18 View Details

A solution of 0.100 M NaOH is mixed with a solution of 0.050 M HCl. What is the pH of the resulting solution?

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 19 View Details

A sample of a gas has a volume of 2.00 L at a pressure of 1.00 atm and a temperature of 25°C. What is the volume of the gas at a pressure of 2.00 atm and a temperature of 50°C?

A. 1.00 L

B. 2.00 L

C. 3.00 L

Correct D. 4.00 L

Correct Answer: D

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Question 20 View Details

A solution of 0.100 M NaOH is mixed with a solution of 0.050 M HCl. What is the concentration of the resulting solution?

A. 0.050 M

B. 0.075 M

Correct C. 0.100 M

D. 0.125 M

Correct Answer: C

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Question 21 View Details

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.

Correct A. -1206.60 kJ/mol

B. -1206.60 kJ/mol

C. -1206.60 kJ/mol

D. -1206.60 kJ/mol

Correct Answer: A

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Question 22 View Details

A 0.500 M solution of NaOH is mixed with a 0.500 M solution of HCl. What is the pH of the resulting solution?

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 23 View Details

A metal (X) reacts with oxygen to form a basic oxide. The reaction is: 4X + 3O2 → 2X2O3. What is the oxidation state of X?

A. +2

Correct B. +3

C. +4

D. +5

Correct Answer: B

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Question 24 View Details

A gas at 25°C and 1 atm is compressed to 2 atm. What is the new volume of the gas?

A. 0.50 L

Correct B. 1.00 L

C. 2.00 L

D. 4.00 L

Correct Answer: B

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Question 25 View Details

A 2.00 M solution of HCl is mixed with a 2.00 M solution of NaOH. What is the resulting concentration of HCl?

A. 0.00 M

Correct B. 1.00 M

C. 2.00 M

D. 4.00 M

Correct Answer: B

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