Practice Post UTME AAUA chemistry 2025 Past Questions

Question 1

Determine the solubility of AgCl in a 0.1 M NaCl solution u\sing the common-ion effect. Assume the solubility product cons\tant (Ksp) for AgCl is 1.8 × 10⁻¹ⁱ.

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 2

A 2.5 g sample of a non-metallic oxide is heated in a stream of CO gas. If 0.75 g of CO is consumed, what is the empirical formula of the oxide?

A. MgO

B. CaO

Correct C. SiO2

D. Al2O3

Correct Answer: C

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Question 3

A gas at 300 K has a pressure of 1.2 atm. If the temperature is increased to 400 K, what is the new pressure?

A. 1.5 atm

Correct B. 2.0 atm

C. 2.5 atm

D. 3.0 atm

Correct Answer: B

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Question 4

A 10 mL sample of a solution containing 0.1 M NaCl is mixed with 20 mL of a solution containing 0.2 M KCl. What is the concentration of Cl- ions in the resulting solution?

A. 0.05 M

B. 0.1 M

Correct C. 0.15 M

D. 0.2 M

Correct Answer: C

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Question 5

A 2.5 g sample of a non-metallic oxide is heated in a stream of CO gas. If 0.75 g of CO is consumed, what is the empirical formula of the oxide?

A. MgO

B. CaO

Correct C. SiO2

D. Al2O3

Correct Answer: C

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Question 6

A 2.50-g sample of a non-metallic oxide of nitrogen is decomposed by heating with graphite in a stream of hydrogen at 1273 K. The volume of hydrogen gas produced at STP is 1.25 dm³. Calculate the empirical formula of the oxide.

A. N₂O

B. NO

C. N₂O₃

Correct D. N₂O₅

Correct Answer: D

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Question 7

A 2.00-g sample of a polymer is dissolved in 50.0 cm³ of benzene. The solution is then titrated with 0.100 M HCl. The volume of HCl required to precipitate the polymer is 25.0 cm³. Calculate the molar mass of the polymer.

A. 1000 g mol⁻¹

B. 1500 g mol⁻¹

Correct C. 2000 g mol⁻¹

D. 2500 g mol⁻¹

Correct Answer: C

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Question 8

A 2.00-g sample of a non-metallic oxide of sulfur is decomposed by heating with graphite in a stream of hydrogen at 1273 K. The volume of hydrogen gas produced at STP is 1.25 dm³. Calculate the empirical formula of the oxide.

A. SO

B. SO₂

Correct C. SO₃

D. SO₄

Correct Answer: C

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Question 9

A 2.00-g sample of a metal is electrolyzed in a solution of 0.100 M HCl. The mass of the metal deposited at the cathode is 1.50 g. Calculate the molar mass of the metal.

A. 1000 g mol⁻¹

B. 1500 g mol⁻¹

C. 2000 g mol⁻¹

Correct D. 2500 g mol⁻¹

Correct Answer: D

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Question 10

A 2.00-g sample of a polymer is dissolved in 50.0 cm³ of benzene. The solution is then titrated with 0.100 M HCl. The volume of HCl required to precipitate the polymer is 25.0 cm³. Calculate the molar mass of the polymer.

A. 1000 g mol⁻¹

B. 1500 g mol⁻¹

Correct C. 2000 g mol⁻¹

D. 2500 g mol⁻¹

Correct Answer: C

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Question 11

The s\tandard Gibbs free energy change (ΔG°) for the reaction 2NO(g) + O2(g) → 2NO2(g) is -110.5 kJ/mol. Calculate the equilibrium cons\tant (K) at 298 K.

Correct A. 1.2 × 10^10

B. 1.2 × 10^5

C. 1.2 × 10^2

D. 1.2 × 10^-2

Correct Answer: A

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Question 12

A 25.0 mL sample of 0.100 M HCl is mixed with a 25.0 mL sample of 0.100 M 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 13

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 separate the titrant and analyte

Correct Answer: A

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Question 14

A 2.50 g sample of a hydrocarbon is burned in a bomb calorimeter, relea\sing 12.5 kJ of heat. What is the molar mass of the hydrocarbon?

A. 50.0 g/mol

Correct B. 75.0 g/mol

C. 100 g/mol

D. 125 g/mol

Correct Answer: B

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Question 15

A solution of 0.100 M NaCl is prepared by dissolving 10.0 g of NaCl in 100 mL of water. What is the concentration of the solution in g/L?

Correct A. 10.0 g/L

B. 20.0 g/L

C. 30.0 g/L

D. 40.0 g/L

Correct Answer: A

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Question 16

Determine the number of stereocenters in the compound below, assuming the molecule is achiral.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 17

What is the major product of the reaction between 2-methyl-2-propanol and HCl?

Correct A. 2-chloro-2-methylpropane

B. 2-chloro-2-methylpropan-2-ol

C. 2-methyl-2-propanol

D. 2-methyl-2-propanone

Correct Answer: A

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Question 18

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 19

What is the molar solubility of CaF2 in a 0.100 M solution of NaF?

Correct A. 0.0100

B. 0.100

C. 1.00

D. 10.0

Correct Answer: A

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Question 20

A sample of a gas at 25°C and 1.00 atm is found to have a volume of 2.50 L. What is the number of moles of gas present?

A. 0.0100

Correct B. 0.100

C. 1.00

D. 10.0

Correct Answer: B

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Question 21

The reaction of sodium hydroxide with acetic acid is represented by the equation: CH3COOH + NaOH → CH3COONa + H2O. If 25.0 mL of 0.500 M acetic acid is mixed with 25.0 mL of 0.500 M sodium hydroxide, what is the limiting reac\tant?

Correct A. Acetic acid

B. Sodium hydroxide

C. Water

D. Sodium acetate

Correct Answer: A

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Question 22

A solution contains 0.100 M NaCl and 0.200 M CaCl2. What is the concentration of Cl- ions in the solution?

A. 0.100 M

B. 0.200 M

Correct C. 0.300 M

D. 0.400 M

Correct Answer: C

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Question 23

The reaction of hydrogen gas with oxygen gas is represented by the equation: 2H2 + O2 → 2H2O. If 1.00 L of hydrogen gas at 25°C and 1.00 atm is mixed with 1.00 L of oxygen gas at 25°C and 1.00 atm, what is the limiting reac\tant?

Correct A. Hydrogen gas

B. Oxygen gas

C. Water

D. None of the above

Correct Answer: A

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Question 24

A solution contains 0.100 M NaOH and 0.200 M HCl. What is the concentration of Na+ ions in 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

The reaction of ammonia with oxygen gas is represented by the equation: 4NH3 + 5O2 → 4NO + 6H2O. If 1.00 L of ammonia gas at 25°C and 1.00 atm is mixed with 1.00 L of oxygen gas at 25°C and 1.00 atm, what is the limiting reac\tant?

Correct A. Ammonia gas

B. Oxygen gas

C. Nitric oxide

D. Water

Correct Answer: A

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