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POST UTME LASU 2017 Chemistry | Objective

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Question 1

A 2.50 g sample of an unknown hydrocarbon is burned in a combustion calorimeter. The volume of carbon dioxide produced is 1.25 L at 25°C and 1 atm. Calculate the empirical formula of the hydrocarbon.

Correct A. C6H12

B. C4H8

C. C3H6

D. C2H4

Correct Answer: A

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Question 2

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

Correct A. 7.00

B. 6.00

C. 5.00

D. 4.00

Correct Answer: A

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Question 3

A 25.0 mL sample of a solution containing 0.100 M KI is mixed with 25.0 mL of a solution containing 0.100 M AgNO3. What is the concentration of the resulting solution?

Correct A. 0.0500 M

B. 0.100 M

C. 0.200 M

D. 0.500 M

Correct Answer: A

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Question 4

A 50.0 mL sample of a solution containing 0.100 M HCl is mixed with 50.0 mL of a solution containing 0.100 M NaOH. What is the pH of the resulting solution?

Correct A. 7.00

B. 6.00

C. 5.00

D. 4.00

Correct Answer: A

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Question 5

A 100.0 mL sample of a solution containing 0.100 M NaOH is mixed with 100.0 mL of a solution containing 0.100 M HCl. What is the pH of the resulting solution?

Correct A. 7.00

B. 6.00

C. 5.00

D. 4.00

Correct Answer: A

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Question 6

At 298 K, the equilibrium cons\tant (Kc) for the reaction N2O4(g) ⇌ 2NO2(g) is 1.8 × 10^\( -2 \). Calculate the equilibrium cons\tant (Kp) for the reaction at the same temperature.

Correct A. 1.8 × 10^\( -1 \)

B. 1.8 × 10^\( -2 \)

C. 1.8 × 10^\( -3 \)

D. 1.8 × 10^\( -4 \)

Correct Answer: A

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Question 7

The reaction between sodium hydroxide (NaOH) and acetic acid (CH3COOH) is represented by the equation: CH3COOH + NaOH → CH3COONa + H2O. If 25.0 mL of 0.100 M CH3COOH is mixed with 25.0 mL of 0.100 M NaOH, what is the concentration of the resulting solution?

A. 0.0500 M

B. 0.100 M

Correct C. 0.150 M

D. 0.200 M

Correct Answer: C

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Question 8

A 2.50-g sample of a polymer is dissolved in 50.0 mL of a solvent. If the solution has a density of 1.00 g/mL, what is the concentration of the polymer in g/mL?

A. 0.0500 g/mL

Correct B. 0.100 g/mL

C. 0.150 g/mL

D. 0.200 g/mL

Correct Answer: B

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Question 9

The s\tandard enthalpy of formation (ΔHf) for the reaction C(s) + O2(g) → CO2(g) is -393.5 kJ/mol. What is the s\tandard enthalpy of formation (ΔHf) for the reaction C(s) + 2H2(g) → CH4(g)?

A. -74.8 kJ/mol

B. -74.9 kJ/mol

Correct C. -75.0 kJ/mol

D. -75.1 kJ/mol

Correct Answer: C

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Question 10

A 1.00-mol sample of a gas is confined to a 2.00-L container at a temperature of 298 K. What is the pressure of the gas in atm?

A. 0.500 atm

Correct B. 1.00 atm

C. 1.50 atm

D. 2.00 atm

Correct Answer: B

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Question 11

In the electrolysis of molten sodium chloride, what is the primary product at the cathode?

Correct A. Sodium

B. Chlorine

C. Sodium chloride

D. Hydrogen

Correct Answer: A

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Question 12

What is the major difference between a polymer and a biomolecule?

Correct A. Polymerization occurs through covalent bonds, while biomolecules are held together by hydrogen bonds.

B. Biomolecules are typically smaller than polymers.

C. Polymers are naturally occurring, while biomolecules are synthesized in the lab.

D. Polymers are biodegradable, while biomolecules are not.

Correct Answer: A

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Question 13

A sample of a non-metallic oxide has a mass of 25.0 g and a volume of 5.00 cm³. What is the molar mass of the oxide?

A. 50.0 g/mol

Correct B. 100.0 g/mol

C. 150.0 g/mol

D. 200.0 g/mol

Correct Answer: B

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Question 14

What is the pH of a solution that is 0.10 M in HCl?

Correct A. 1.0

B. 2.0

C. 3.0

D. 4.0

Correct Answer: A

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Question 15

A solution contains 0.50 M H₂SO₄ and 0.50 M NaOH. 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 16

The s\tandard electrode potential of the couple Mn2+/Mn is -1.18 V. Calculate the s\tandard electrode potential of the couple MnO4-/Mn2+.

Correct A. -0.59 V

B. -0.79 V

C. -1.18 V

D. -1.58 V

Correct Answer: A

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Question 17

A solution contains 0.1 M Fe2+ ions. If 50.0 mL of 0.1 M NaOH is added to 100.0 mL of the solution, what is the concentration of Fe(OH)3 formed?

A. 0.01 M

B. 0.02 M

Correct C. 0.03 M

D. 0.04 M

Correct Answer: C

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Question 18

The half-life of a radioactive subs\tance is 10 years. If 100 g of the subs\tance is present initially, what is the mass of the subs\tance remaining after 30 years?

Correct A. 6.25 g

B. 12.5 g

C. 25.0 g

D. 50.0 g

Correct Answer: A

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Question 19

A solution contains 0.1 M HCl. If 50.0 mL of 0.1 M NaOH is added to 100.0 mL of the solution, what is the pH of the resulting solution?

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 20

A metal M has a s\tandard electrode potential of +0.5 V. If a solution contains 0.1 M M2+ ions, what is the concentration of M that can be reduced at the cathode?

A. 0.01 M

B. 0.02 M

Correct C. 0.03 M

D. 0.04 M

Correct Answer: C

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Question 21

A solution contains 0.1 M Fe2+ ions. If 50.0 mL of 0.1 M NaOH is added to 100.0 mL of the solution, what is the concentration of Fe(OH)3 formed?

A. 0.01 M

B. 0.02 M

Correct C. 0.03 M

D. 0.04 M

Correct Answer: C

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Question 22

A metal M has a s\tandard electrode potential of +0.5 V. If a solution contains 0.1 M M2+ ions, what is the concentration of M that can be reduced at the cathode?

A. 0.01 M

B. 0.02 M

Correct C. 0.03 M

D. 0.04 M

Correct Answer: C

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Question 23

A solution contains 0.1 M HCl. If 50.0 mL of 0.1 M NaOH is added to 100.0 mL of the solution, what is the pH of the resulting solution?

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 24

A metal M has a s\tandard electrode potential of +0.5 V. If a solution contains 0.1 M M2+ ions, what is the concentration of M that can be reduced at the cathode?

A. 0.01 M

B. 0.02 M

Correct C. 0.03 M

D. 0.04 M

Correct Answer: C

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Question 25

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of CaCO3(s) u\sing the following reaction: CaO(s) + CO2(g) → CaCO3(s).

Correct A. -1782.5 kJ/mol

B. -1782.8 kJ/mol

C. -1782.2 kJ/mol

D. -1782.1 kJ/mol

Correct Answer: A

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