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POST UTME AAUA 2019 Chemistry | Objective

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Question 1

Calculate the s\tandard enthalpy change \( ΔH^circ \) for the reaction: 2Al(s) + Fe_2O_3(s) → 2Fe(s) + Al_2O_3(s). Given that the s\tandard enthalpy of formation \( ΔH^circ_f \) for Al_2O_3(s) is -1675.7 kJ/mol, and the s\tandard enthalpy of formation for Fe(s) is 0 kJ/mol. The s\tandard enthalpy of formation for Al(s) is 0 kJ/mol, and the s\tandard enthalpy of formation for Fe_2O_3(s) is -826.4 kJ/mol.

Correct A. -1011.1 kJ/mol

B. -1011.2 kJ/mol

C. -1011.3 kJ/mol

D. -1011.4 kJ/mol

Correct Answer: A

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Question 2

A 0.5 M solution of NaOH is mixed with a 0.5 M solution of HCl. Calculate the pH of the resulting solution after the reaction is complete.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 3

A metal (M) reacts with oxygen to form a basic oxide. The oxide is soluble in water to form a solution with a pH of 10. The metal (M) is most likely to be

Correct A. Ca

B. Mg

C. Al

D. Zn

Correct Answer: A

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Question 4

A solution of 0.1 M NaCl is prepared by dissolving 0.1 g of NaCl in 100 mL of water. Calculate the concentration of the solution in g/L.

Correct A. 0.1 g/L

B. 0.2 g/L

C. 0.3 g/L

D. 0.4 g/L

Correct Answer: A

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Question 5

A 2 M solution of HCl is mixed with a 2 M solution of NaOH. Calculate the pH of the resulting solution after the reaction is complete.

A. 0

Correct B. 1

C. 2

D. 3

Correct Answer: B

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Question 6

In a redox reaction, what is the role of the oxidizing agent?

A. To donate electrons

Correct B. To accept electrons

C. To facilitate the reaction

D. To inhibit the reaction

Correct Answer: B

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Question 7

A solution of 0.1 M NaOH is titrated with 0.1 M HCl. What is the pH of the solution after the reaction is complete?

Correct A. 7

B. 10

C. 14

D. 12

Correct Answer: A

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Question 8

A polymer has a molecular weight of 100,000 g/mol. What is the number of monomer units in the polymer?

A. 100

B. 1000

Correct C. 10,000

D. 100,000

Correct Answer: C

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Question 9

A cell has a s\tandard electrode potential of 0.5 V. What is the cell potential at 25°C and 1 atm?

Correct A. 0.5 V

B. 0.6 V

C. 0.7 V

D. 0.8 V

Correct Answer: A

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Question 10

A solution of 0.1 M HCl is titrated with 0.1 M NaOH. What is the pH of the solution after the reaction is complete?

Correct A. 7

B. 10

C. 14

D. 12

Correct Answer: A

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Question 11

In a redox reaction, what is the role of the oxidizing agent?

A. To gain electrons

Correct B. To lose electrons

C. To facilitate the transfer of electrons

D. To inhibit the reaction

Correct Answer: B

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Question 12

A 2.5 L flask contains 0.5 mol of an ideal gas at 27°C. Calculate the pressure of the gas u\sing the ideal gas law.

A. 1.01 x 10^5 Pa

Correct B. 2.01 x 10^5 Pa

C. 3.01 x 10^5 Pa

D. 4.01 x 10^5 Pa

Correct Answer: B

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Question 13

A solution contains 0.1 M NH3 and 0.2 M HCl. What is the pH of the solution?

A. 1.0

Correct B. 2.0

C. 3.0

D. 4.0

Correct Answer: B

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Question 14

A 5.0 g sample of a non-metallic element is heated in a crucible until it reaches a temperature of 2500°C. What is the mass of the element that sublimes?

A. 2.5 g

Correct B. 3.5 g

C. 4.5 g

D. 5.5 g

Correct Answer: B

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Question 15

A 1.0 L flask contains 0.5 mol of an ideal gas at 27°C. What is the volume of the gas at 37°C?

A. 1.5 L

Correct B. 2.0 L

C. 2.5 L

D. 3.0 L

Correct Answer: B

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Question 16

A polymer is formed by the condensation reaction between two monomers, A and B. If the molecular weight of the polymer is 100,000 g/mol, and the molecular weights of A and B are 50,000 g/mol and 30,000 g/mol, respectively, what is the average molecular weight of the monomers that reacted to form the polymer?

A. 40,000 g/mol

B. 50,000 g/mol

Correct C. 60,000 g/mol

D. 70,000 g/mol

Correct Answer: C

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Question 17

A solution of NaCl is prepared by dissolving 35.5 g of NaCl in 100 mL of water. If the density of the solution is 1.05 g/mL, what is the molarity of the solution?

A. 0.5 M

Correct B. 1.0 M

C. 1.5 M

D. 2.0 M

Correct Answer: B

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Question 18

A colloid is formed by disper\sing 10 g of silica in 100 mL of water. If the density of the silica is 2.5 g/mL, what is the volume percentage of the silica in the colloid?

A. 10%

Correct B. 20%

C. 30%

D. 40%

Correct Answer: B

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Question 19

A periodic table is shown below. Which element has the highest electronegativity?

Correct A. Fluorine

B. Chlorine

C. Bromine

D. Iodine

Correct Answer: A

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Question 20

A redox reaction is shown below. What is the oxidation state of the manganese ion?

A. +2

Correct B. +3

C. +4

D. +5

Correct Answer: B

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Question 21

Determine the s\tandard enthalpy change for the reaction: 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s). The s\tandard enthalpy of formation for Al2O3(s) is -1675 kJ/mol, and the s\tandard enthalpy of formation for Fe2O3(s) is -824 kJ/mol. The s\tandard enthalpy of formation for Al(s) is 0 kJ/mol, and the s\tandard enthalpy of formation for Fe(s) is 0 kJ/mol.

Correct A. -1829 kJ/mol

B. -1675 kJ/mol

C. -824 kJ/mol

D. -2869 kJ/mol

Correct Answer: A

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Question 22

A 0.500 M solution of HCl is mixed with a 0.500 M solution of NaOH. 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

A sample of a polymer has a molecular weight of 100,000 g/mol. If the polymer has a density of 1.5 g/cm^3, what is the volume of the polymer sample?

A. 0.067 cm^3

Correct B. 0.067 L

C. 0.067 m^3

D. 0.067 mL

Correct Answer: B

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Question 24

A 2.00 M solution of H2SO4 is mixed with a 2.00 M solution of NaOH. What is the concentration of the resulting solution?

Correct A. 1.00 M

B. 2.00 M

C. 3.00 M

D. 4.00 M

Correct Answer: A

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Question 25

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

A. 0.500 M

Correct B. 1.00 M

C. 1.50 M

D. 2.00 M

Correct Answer: B

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