Practice Post UTME AAUA chemistry 2020 Past Questions

Question 1

A 2.5 g sample of a non-metallic oxide of nitrogen is decomposed by heating with graphite in a stream of hydrogen. The volume of hydrogen gas produced at 25°C and 1 atm is 2.5 L. Calculate the molar mass of the oxide.

A. 60 g/mol

B. 80 g/mol

Correct C. 100 g/mol

D. 120 g/mol

Correct Answer: C

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Question 2

A solution of a non-metallic oxide of nitrogen in water has a pH of 9.5. Calculate the concentration of the oxide in moles per liter.

Correct A. 0.01 M

B. 0.05 M

C. 0.1 M

D. 0.2 M

Correct Answer: A

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Question 3

A 10% solution of a non-metallic oxide of nitrogen in water has a density of 1.2 g/mL. Calculate 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 4

A 2.5 g sample of a non-metallic oxide of nitrogen is decomposed by heating with graphite in a stream of hydrogen. The volume of hydrogen gas produced at 25°C and 1 atm is 2.5 L. Calculate the percentage yield of the reaction.

A. 50%

B. 60%

Correct C. 70%

D. 80%

Correct Answer: C

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Question 5

A solution of a non-metallic oxide of nitrogen in water has a pH of 9.5. Calculate the concentration of the oxide in moles per liter.

Correct A. 0.01 M

B. 0.05 M

C. 0.1 M

D. 0.2 M

Correct Answer: A

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Question 6

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. -1785.6 kJ/mol

B. -1785.9 kJ/mol

C. -1786.1 kJ/mol

D. -1786.3 kJ/mol

Correct Answer: A

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Question 7

A metal (M) reacts with chlorine gas to form a white solid. The reaction is highly exothermic. What is the likely identity of the metal?

A. Na

B. K

C. Ca

Correct D. Mg

Correct Answer: D

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Question 8

A 2.50 g sample of a non-metallic element (X) is heated in a crucible to produce 1.25 g of X2O5. What is the empirical formula of the element?

A. O2S

Correct B. SO2

C. SO3

D. SO4

Correct Answer: B

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Question 9

A 25.0 mL sample of a 0.100 M solution of NaOH is titrated with 0.100 M HCl. What is the pH of the resulting solution?

A. 7.00

Correct B. 7.50

C. 8.00

D. 9.00

Correct Answer: B

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Question 10

A 50.0 mL sample of a 0.500 M solution of H2SO4 is mixed with 50.0 mL of a 0.500 M solution of NaOH. What is the resulting pH?

A. 1.00

B. 2.00

Correct C. 3.00

D. 4.00

Correct Answer: C

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Question 11

Determine the oxidation state of the underlined atom in the compound H2SO4.

Correct A. +6

B. +4

C. +2

D. +1

Correct Answer: A

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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. 2.02 x 10^5 Pa

C. 3.03 x 10^5 Pa

D. 4.04 x 10^5 Pa

Correct Answer: B

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Question 13

A solution contains 0.1 M NaCl. If 10 mL of this solution is diluted to 100 mL, what is the concentration of the resulting solution?

Correct A. 0.01 M

B. 0.1 M

C. 1 M

D. 10 M

Correct Answer: A

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Question 14

The diagram below shows a setup for electrolysis. Identify the product formed at the cathode.

Correct A. H2

B. O2

C. Na

D. Cl2

Correct Answer: A

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Question 15

A 0.1 M solution of HCl is mixed with a 0.1 M solution of NaOH. What is the pH of the resulting solution?

A. 1

Correct B. 7

C. 10

D. 14

Correct Answer: B

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Question 16

Determine the molar solubility of BaSO4 in 0.1 M Na2SO4 solution.

A. 1.0 x 10^-3 M

B. 1.0 x 10^-2 M

Correct C. 1.0 x 10^-4 M

D. 1.0 x 10^-5 M

Correct Answer: C

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Question 17

A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the pH of the solution after 15.0 mL of NaOH has been added.

A. 2.00

Correct B. 2.50

C. 3.00

D. 3.50

Correct Answer: B

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Question 18

The diagram below shows the structure of a hydrocarbon. What is the name of the compound?

Correct A. Cyclohexane

B. Cyclohexene

C. Benzene

D. Toluene

Correct Answer: A

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Question 19

A solution contains 0.0500 M NH3 and 0.0500 M NH4Cl. What is the pH of the solution?

A. 9.25

Correct B. 9.50

C. 9.75

D. 10.00

Correct Answer: B

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Question 20

The diagram below shows a titration setup. What is the purpose of the burette?

Correct A. To measure the volume of the titrant

B. To measure the volume of the analyte

C. To mix the titrant and analyte

D. To measure the pH of the solution

Correct Answer: A

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Question 21

Determine the oxidation state of the underlined metal atom in the compound [Cr(H2O)6]Cl3.

Correct A. +3

B. +2

C. +1

D. +6

Correct Answer: A

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Question 22

The diagram below shows a titration setup. What is the purpose of the burette?

Correct A. To measure the volume of the titrant

B. To measure the volume of the analyte

C. To mix the titrant and analyte

D. To filter the solution

Correct Answer: A

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Question 23

Calculate the pH of a solution containing 0.1 M HCl and 0.1 M NaOH.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 24

The diagram below shows a molecular structure. What is the type of bond between the two atoms?

Correct A. Covalent

B. Ionic

C. Hydrogen

D. Polar Covalent

Correct Answer: A

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Question 25

The reaction below is an example of a redox reaction. What is the oxidation state of the underlined atom?

A. +2

B. +1

Correct C. +3

D. +4

Correct Answer: C

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