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POST UTME LASU 2023 Chemistry | Objective

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Question 1

Determine the number of moles of nitrogen gas (N2) produced when 2.5 g of ammonia (NH3) is decomposed at cons\tant volume and temperature.

A. 0.05 mol

Correct B. 0.1 mol

C. 0.15 mol

D. 0.2 mol

Correct Answer: B

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Question 2

A 0.1 M solution of sodium hydroxide (NaOH) is mixed with a 0.2 M solution of hydrochloric acid (HCl). Determine the pH of the resulting solution.

A. 1

B. 2

Correct C. 3

D. 4

Correct Answer: C

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Question 3

A diagram of a redox reaction is shown below.

A. Oxidation occurs at A

B. Reduction occurs at A

C. Oxidation occurs at B

Correct D. Reduction occurs at B

Correct Answer: D

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Question 4

A 1.0 M solution of potassium chloride (KCl) is electrolyzed at a cons\tant current of 1.0 A for 10 minutes. Determine the mass of potassium chloride deposited at the cathode.

A. 0.1 g

B. 0.2 g

Correct C. 0.3 g

D. 0.4 g

Correct Answer: C

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Question 5

A diagram of a titration setup is shown below.

A. The burette contains the analyte

Correct B. The burette contains the titrant

C. The beaker contains the analyte

D. The beaker contains the titrant

Correct Answer: B

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Question 6

The reaction of cyclohexane with bromine in the presence of light results in the formation of a cyclic bromohydrocarbon. What is the major product of this reaction?

A. 1-bromocyclohexane

Correct B. trans-1,2-dibromocyclohexane

C. cis-1,2-dibromocyclohexane

D. cyclohexene

Correct Answer: B

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Question 7

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of H2O(l) if the s\tandard enthalpy of formation of H2(g) is 0 kJ/mol and the s\tandard enthalpy of formation of O2(g) is 0 kJ/mol?

Correct A. -285.8 kJ/mol

B. -241.8 kJ/mol

C. -393.5 kJ/mol

D. -572.8 kJ/mol

Correct Answer: A

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Question 8

A 2.5 M solution of HCl is mixed with a 1.5 M solution of NaOH. What is the concentration of the resulting solution?

A. 1.5 M

Correct B. 2.0 M

C. 2.5 M

D. 3.0 M

Correct Answer: B

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Question 9

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 10

The reaction of methane with chlorine in the presence of light results in the formation of a chlorinated hydrocarbon. What is the major product of this reaction?

A. CH3Cl

Correct B. CH2Cl2

C. CHCl3

D. CCl4

Correct Answer: B

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Question 11

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. -1206.60 kJ/mol

B. -1206.61 kJ/mol

C. -1206.59 kJ/mol

D. -1206.62 kJ/mol

Correct Answer: A

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Question 12

A 2.5 L flask contains 0.25 mol of an ideal gas at 25°C. Calculate the pressure of the gas u\sing the ideal gas law.

Correct A. 1.01 × 10^5 Pa

B. 2.02 × 10^5 Pa

C. 3.03 × 10^5 Pa

D. 4.04 × 10^5 Pa

Correct Answer: A

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Question 13

A solution contains 0.1 M NaCl. Calculate the concentration of Cl- ions in the solution.

A. 0.05 M

Correct B. 0.1 M

C. 0.15 M

D. 0.2 M

Correct Answer: B

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Question 14

A 10 mL sample of a solution contains 0.5 g of glu\cose. Calculate the molarity of the solution.

A. 0.1 M

Correct B. 0.2 M

C. 0.3 M

D. 0.4 M

Correct Answer: B

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Question 15

A 5 L flask contains 0.5 mol of an ideal gas at 50°C. Calculate the volume of the gas u\sing the ideal gas law.

A. 2.5 L

Correct B. 5 L

C. 7.5 L

D. 10 L

Correct Answer: B

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Question 16

A sample of a gas at 300 K is compressed from 10 L to 5 L. If the initial pressure is 1.5 atm, what is the final pressure in atm?

A. 1.5 atm

Correct B. 2.25 atm

C. 3 atm

D. 4 atm

Correct Answer: B

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Question 17

A solution contains 10 g of NaCl. If 50 mL of water is added, what is the new concentration in g/L?

A. 0.2 g/L

Correct B. 0.5 g/L

C. 1 g/L

D. 2 g/L

Correct Answer: B

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Question 18

A metal is extracted from its ore u\sing the following process: Roasting → Leaching → Purification. What is the purpose of the roasting step?

Correct A. To convert the ore into a soluble compound

B. To remove impurities from the ore

C. To increase the surface area of the ore

D. To reduce the temperature of the ore

Correct Answer: A

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Question 19

A 10 L \tank contains 5 g of CO2 at 300 K. If the \tank is heated to 400 K, what is the new pressure in atm?

A. 1 atm

B. 2 atm

Correct C. 3 atm

D. 4 atm

Correct Answer: C

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Question 20

A solution contains 20 g of glu\cose. If 100 mL of water is added, what is the new concentration in g/L?

A. 0.2 g/L

B. 0.5 g/L

Correct C. 1 g/L

D. 2 g/L

Correct Answer: C

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Question 21

A polymer is formed by the condensation reaction between a diol and a diacid. If the molecular weight of the diol is 180 g/mol and the molecular weight of the diacid is 150 g/mol, what is the molecular weight of the polymer formed?

A. 390

B. 420

Correct C. 450

D. 480

Correct Answer: C

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Question 22

A solution of sodium chloride is prepared by dissolving 35.5 g of sodium chloride in 100 mL of water. What is the molarity of the solution?

A. 0.6

B. 0.7

Correct C. 0.8

D. 0.9

Correct Answer: C

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Question 23

A 0.1 M solution of hydrochloric acid is prepared by dissolving 3.0 g of hydrochloric acid in 100 mL of water. What is the pH of the solution?

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 24

A metal oxide is formed by the reaction between a metal and oxygen. If the metal has an atomic mass of 40 g/mol and the oxygen has an atomic mass of 16 g/mol, what is the empirical formula of the metal oxide?

Correct A. MgO

B. CaO

C. FeO

D. CuO

Correct Answer: A

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Question 25

A non-metal is formed by the reaction between a metal and a non-metal. If the metal has an atomic mass of 24 g/mol and the non-metal has an atomic mass of 32 g/mol, what is the empirical formula of the non-metal?

A. C

B. N

C. O

Correct D. S

Correct Answer: D

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