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POST UTME ABU 2019 Chemistry | Objective

Are you preparing for POST UTME ABU exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2019 Chemistry (Objective) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1

Determine the number of moles of oxygen gas (O2) that will react with 2.5 moles of carbon monoxide (CO) according to the balanced equation: 2CO + O2 → 2CO2.

Correct A. 1.25 moles

B. 2.5 moles

C. 5 moles

D. 10 moles

Correct Answer: A

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Question 2

A polymer is made up of repeating units of the following monomer: CH2=CH-CH3. What is the molecular formula of the polymer?

Correct A. \( CH2-CH2-CH3 \)n

B. \( CH2=CH-CH3 \)n

C. \( CH2=CH \)n

D. \( CH2-CH \)n

Correct Answer: A

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Question 3

A solution of 2.0 g of sodium chloride (NaCl) in 100 mL of water has a boiling point elevation of 0.50°C. What is the molar mass of NaCl?

Correct A. 58.5 g/mol

B. 59.5 g/mol

C. 60.5 g/mol

D. 61.5 g/mol

Correct Answer: A

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Question 4

A sample of a gas occupies a volume of 2.5 L at a pressure of 1.5 atm. What is the volume of the gas at a pressure of 3.0 atm, assuming the temperature remains cons\tant?

A. 1.0 L

Correct B. 1.5 L

C. 2.0 L

D. 2.5 L

Correct Answer: B

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Question 5

A solution of 10.0 g of glu\cose (C6H12O6) in 100 mL of water has a freezing point depression of 1.5°C. What is the molar mass of glu\cose?

Correct A. 180 g/mol

B. 182 g/mol

C. 184 g/mol

D. 186 g/mol

Correct Answer: A

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Question 6

The rate cons\tant (k) for a first-order reaction is given by the equation: k = Ae^\( -Ea/RT \). If the activation energy (Ea) is 100 kJ/mol, the gas cons\tant (R) is 8.314 J/\( mol*K \), and the temperature (T) is 300 K, calculate the rate cons\tant (k) when the pre-exponential factor (A) is 1.0 x 10^10 s^\( -1 \).

Correct A. 1.0 x 10^\( -5 \) s^\( -1 \)

B. 1.0 x 10^\( -4 \) s^\( -1 \)

C. 1.0 x 10^\( -3 \) s^\( -1 \)

D. 1.0 x 10^\( -2 \) s^\( -1 \)

Correct Answer: A

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Question 7

The half-life \( t1/2 \) of a radioactive subs\tance is given by the equation: t1/2 = ln(2) * \sigma / \( \mu * c^2 \), where \sigma is the cross-sectional area, \mu is the mass density, and c is the speed of light. If the half-life is 10 years, the cross-sectional area is 1.0 x 10^\( -20 \) m^2, the mass density is 1.0 x 10^3 kg/m^3, and the speed of light is 3.0 x 10^8 m/s, calculate the mass density \( \mu \).

Correct A. 1.0 x 10^\( -3 \) kg/m^3

B. 1.0 x 10^\( -2 \) kg/m^3

C. 1.0 x 10^\( -1 \) kg/m^3

D. 1.0 x 10^0 kg/m^3

Correct Answer: A

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Question 8

The equilibrium cons\tant (K) for a reaction is given by the equation: K = [A]^2 / [B]. If the concentration of A is 1.0 x 10^\( -3 \) M and the concentration of B is 1.0 x 10^\( -4 \) M, calculate the equilibrium cons\tant (K).

Correct A. 1.0 x 10^3

B. 1.0 x 10^4

C. 1.0 x 10^5

D. 1.0 x 10^6

Correct Answer: A

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Question 9

The atomic radius (r) of an atom is given by the equation: r = \( n^2 / Z \) * a0, where n is the principal quantum number, Z is the atomic number, and a0 is the Bohr radius. If the atomic number is 6, the principal quantum number is 2, and the Bohr radius is 5.29 x 10^\( -11 \) m, calculate the atomic radius (r).

A. 2.5 x 10^\( -11 \) m

Correct B. 5.0 x 10^\( -11 \) m

C. 7.5 x 10^\( -11 \) m

D. 1.0 x 10^\( -10 \) m

Correct Answer: B

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Question 10

The bond length (d) of a diatomic molecule is given by the equation: d = \( n^2 / Z \) * a0, where n is the principal quantum number, Z is the atomic number, and a0 is the Bohr radius. If the atomic number is 8, the principal quantum number is 3, and the Bohr radius is 5.29 x 10^\( -11 \) m, calculate the bond length (d).

A. 1.0 x 10^\( -10 \) m

B. 2.0 x 10^\( -10 \) m

Correct C. 3.0 x 10^\( -10 \) m

D. 4.0 x 10^\( -10 \) m

Correct Answer: C

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Question 11

Determine the rate cons\tant (k) for the first-order reaction: A → B, given that the initial concentration of A is 0.1 M and the concentration of A after 2 hours is 0.05 M. The rate cons\tant is related to the half-life \( t1/2 \) of the reaction by the equation: k = ln(2) / t1/2.

Correct A. 0.693 h^-1

B. 1.386 h^-1

C. 2.772 h^-1

D. 3.464 h^-1

Correct Answer: A

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Question 12

A polymer has a molecular weight of 50000 g/mol and a degree of polymerization (DP) of 200. Calculate the molar mass of the repeating unit \( M_r \) of the polymer.

A. 250 g/mol

Correct B. 500 g/mol

C. 750 g/mol

D. 1000 g/mol

Correct Answer: B

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Question 13

A solution of 0.1 M NaCl is prepared by dissolving 6.0 g of NaCl in 100 mL of water. Calculate the molar solubility of NaCl in the solution.

A. 0.01 M

B. 0.05 M

Correct C. 0.1 M

D. 0.5 M

Correct Answer: C

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Question 14

A 10 mL sample of a solution containing 0.1 M Fe^2+ ions is titrated with 0.1 M NaOH solution. Calculate the volume of NaOH required to reach the equivalence point.

A. 5 mL

Correct B. 10 mL

C. 20 mL

D. 50 mL

Correct Answer: B

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Question 15

A metal has a density of 8.0 g/cm^3 and a molar mass of 60 g/mol. Calculate the number of moles of metal present in a 10 g sample.

A. 0.1 mol

Correct B. 0.2 mol

C. 0.3 mol

D. 0.4 mol

Correct Answer: B

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Question 16

The reaction of an alkane with chlorine in the presence of light produces a dichloroalkane. What is the major product of this reaction?

Correct A. 1,2-dichloropropane

B. 1,3-dichloropropane

C. 1,4-dichloropropane

D. 1,5-dichloropen\tane

Correct Answer: A

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Question 17

A sample of nitrogen gas at 25°C and 1 atm is heated to 50°C. What is the new volume of the gas?

A. 2.25 L

Correct B. 2.50 L

C. 2.75 L

D. 3.00 L

Correct Answer: B

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Question 18

A solution of sodium hydroxide is added to a solution of acetic acid. What is the resulting product?

Correct A. sodium acetate

B. acetic acid

C. water

D. carbon dioxide

Correct Answer: A

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Question 19

A sample of oxygen gas at 20°C and 2 atm is mixed with a sample of nitrogen gas at 20°C and 3 atm. What is the resulting partial pressure of oxygen?

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 20

A sample of hydrogen gas at 25°C and 1 atm is mixed with a sample of oxygen gas at 25°C and 1 atm. What is the resulting product?

Correct A. water

B. hydrogen peroxide

C. oxygen

D. hydrogen

Correct Answer: A

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Question 21

A 3.00 g sample of a metal oxide is heated in a crucible until it decomposes completely. The mass of the metal obtained is 1.50 g. Calculate the percentage of metal in the original sample.

A. 30.0%

B. 40.0%

Correct C. 50.0%

D. 60.0%

Correct Answer: C

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Question 22

The reaction between hydrogen gas and chlorine gas is highly exothermic. The reaction is represented by the equation: 2H2(g) + Cl2(g) → 2HCl(g). If 2.00 g of H2 is mixed with 3.00 g of Cl2, what is the limiting reac\tant?

Correct A. H2

B. Cl2

C. Both are in excess

D. Neither is in excess

Correct Answer: A

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Question 23

A 2.00 M solution of NaOH is mixed with a 2.00 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 24

A 1.00 g sample of a metal is heated in a crucible until it decomposes completely. The mass of the metal oxide obtained is 1.50 g. What is the percentage of oxygen in the original sample?

A. 20.0%

B. 30.0%

Correct C. 40.0%

D. 50.0%

Correct Answer: C

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Question 25

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

A. 1.00

B. 2.00

C. 3.00

Correct D. 4.00

Correct Answer: D

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