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POST UTME KSU 2025 Chemistry | Objective

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Question 1

The reaction between chlorine gas and sodium hydroxide solution is represented by the equation: Cl2 + 2NaOH → NaCl + NaClO + H2O. What is the oxidation state of chlorine in the product NaClO?

A. 0

B. +1

C. +2

Correct D. +3

Correct Answer: D

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Question 2

A 2.5 M solution of HCl is prepared by dissolving 12.5 g of HCl in water to make 1 L of solution. What is the pH of the solution?

Correct A. 1.0

B. 2.0

C. 3.0

D. 4.0

Correct Answer: A

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Question 3

The s\tandard enthalpy of formation of CO2 is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of CO?

Correct A. -110.5

B. -130.5

C. -150.5

D. -170.5

Correct Answer: A

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Question 4

A solution of 0.1 M HCl is prepared by dissolving 0.1 g of HCl in water to make 1 L of solution. What is the concentration of H+ ions in the solution?

A. 0.01 M

Correct B. 0.1 M

C. 1.0 M

D. 10.0 M

Correct Answer: B

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Question 5

The reaction between sodium hydroxide and sulfuric acid is represented by the equation: 2NaOH + H2SO4 → Na2SO4 + 2H2O. What is the oxidation state of sulfur in the product Na2SO4?

A. +2

B. +4

Correct C. +6

D. +8

Correct Answer: C

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Question 6

A 2.50 g sample of a hydrocarbon is burned in a bomb calorimeter, relea\sing 11.2 kJ of heat energy. If the molar mass of the hydrocarbon is 42.0 g/mol, calculate the s\tandard enthalpy of combustion per mole of the hydrocarbon.

Correct A. -88.0 kJ/mol

B. -92.0 kJ/mol

C. -96.0 kJ/mol

D. -100.0 kJ/mol

Correct Answer: A

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Question 7

A solution of 0.100 M NaCl is prepared by dissolving 6.0 g of NaCl in 1.0 L of water. What is the concentration of Cl- ions in the solution?

A. 0.050 M

Correct B. 0.100 M

C. 0.150 M

D. 0.200 M

Correct Answer: B

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Question 8

A mixture of 25.0 g of C6H12O6 and 15.0 g of C2H5OH is burned in a bomb calorimeter, relea\sing 43.2 kJ of heat energy. If the molar mass of C6H12O6 is 180.0 g/mol and the molar mass of C2H5OH is 46.0 g/mol, calculate the s\tandard enthalpy of combustion per mole of the mixture.

Correct A. -98.0 kJ/mol

B. -102.0 kJ/mol

C. -106.0 kJ/mol

D. -110.0 kJ/mol

Correct Answer: A

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Question 9

A 1.00 L sample of a solution containing 0.050 M NaOH and 0.050 M HCl is titrated with 0.100 M HCl. What is the pH of the solution after the titration?

A. 7.00

Correct B. 7.50

C. 8.00

D. 9.00

Correct Answer: B

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Question 10

A 2.00 L sample of a solution containing 0.050 M NaOH and 0.050 M HCl is titrated with 0.100 M HCl. What is the pH of the solution after the titration?

A. 7.00

Correct B. 7.50

C. 8.00

D. 9.00

Correct Answer: B

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Question 11

The reaction of cyclohexane with bromine in the presence of light produces a mixture of 1,2-dibromocyclohexane and 1,4-dibromocyclohexane. What is the major product of this reaction?

A. 1,2-dibromocyclohexane

Correct B. 1,4-dibromocyclohexane

C. cis-1,2-dibromocyclohexane

D. trans-1,2-dibromocyclohexane

Correct Answer: B

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Question 12

The following diagram shows the structure of a compound. What is the name of this compound?

Correct A. Ethanol

B. Propanol

C. Bu\tanol

D. Pen\tanol

Correct Answer: A

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Question 13

The half-life of a radioactive subs\tance is 5 years. If the initial amount of the subs\tance is 100g, what is the amount remaining after 10 years?

Correct A. 12.5g

B. 25g

C. 50g

D. 100g

Correct Answer: A

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Question 14

The following diagram shows the structure of a molecule. What is the type of bond between atoms A and B?

Correct A. Covalent bond

B. Ionic bond

C. Hydrogen bond

D. Van der Waals force

Correct Answer: A

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Question 15

The reaction of sodium with water produces hydrogen gas and sodium hydroxide. What is the balanced chemical equation for this reaction?

Correct A. \( 2Na + 2H_2O \rightarrow 2NaOH + H_2 \)

B. \( 2Na + 2H_2O \rightarrow 2NaOH + 2H_2 \)

C. \( 2Na + 2H_2O \rightarrow 2NaOH + H_2O \)

D. \( 2Na + 2H_2O \rightarrow 2NaOH + 2H_2O \)

Correct Answer: A

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Question 16

The rate cons\tant for a first-order reaction is 0.05 min^-1. If the initial concentration of the reac\tant is 0.1 M, what is the concentration of the reac\tant after 10 minutes?

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 17

A sample of a gas occupies a volume of 2.5 L at a pressure of 1.5 atm. If the temperature is increased to 300 K, what is the new volume of the gas?

A. 3.0 L

B. 3.5 L

Correct C. 4.0 L

D. 4.5 L

Correct Answer: C

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Question 18

The half-life of a radioactive subs\tance is 5 years. If the initial amount of the subs\tance is 100 g, what is the amount of the subs\tance remaining after 10 years?

Correct A. 12.5 g

B. 25 g

C. 50 g

D. 100 g

Correct Answer: A

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Question 19

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

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 20

A sample of a subs\tance has a mass of 25 g. If the density of the subs\tance is 2.5 g/mL, what is the volume of the subs\tance?

A. 10 mL

B. 20 mL

Correct C. 25 mL

D. 30 mL

Correct Answer: C

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Question 21

A solution contains 0.1 M NaOH. If 10 mL of this solution is added to 100 mL of 0.1 M HCl, what is the resulting pH of the solution?

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 22

A sample of a gas occupies a volume of 2.5 L at a pressure of 1.5 atm. If the temperature is increased to 300 K, what is the new pressure of the gas?

A. 2.0 atm

B. 2.5 atm

Correct C. 3.0 atm

D. 3.5 atm

Correct Answer: C

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Question 23

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

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 24

A sample of a subs\tance has a mass of 25 g. If the density of the subs\tance is 2.5 g/mL, what is the volume of the subs\tance?

A. 10 mL

B. 20 mL

Correct C. 25 mL

D. 30 mL

Correct Answer: C

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Question 25

The reaction between potassium permanganate and hydrogen peroxide is a classic example of a redox reaction. Which of the following is the correct representation of the reaction in terms of half-equations?

A. \[ \text{MnO}_4^- + 2H_2O \rightarrow \text{Mn}^2+ + 4OH^- \]

B. \[ \text{H}_2O_2 + 2H^+ \rightarrow 2H_2O \]

Correct C. \[ \text{MnO}_4^- + 8H^+ + 5e^- \rightarrow \text{Mn}^2+ + 4H_2O \]

D. \[ \text{H}_2O_2 + 2H^+ \rightarrow 2H_2O \]

Correct Answer: C

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