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POST UTME SUMMIT UNIVERSITY 2017 Chemistry | Objective

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Question 1

A 2.50 g sample of a metal oxide is heated in a crucible until it decomposes completely. The mass of the metal obtained is 1.75 g. If the metal oxide has a molar mass of 120 g/mol, calculate the percentage yield of the metal.

A. 85%

B. 90%

Correct C. 95%

D. 80%

Correct Answer: C

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Question 2

A 0.500 L sample of a gas at 25°C and 1.00 atm is allowed to expand to 1.50 L at cons\tant temperature. Calculate the work done by the gas.

Correct A. -0.750 L atm

B. -0.500 L atm

C. -1.00 L atm

D. -1.50 L atm

Correct Answer: A

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Question 3

A 2.00 M solution of HCl is mixed with a 1.00 M solution of NaOH. If 25.0 mL of the HCl solution is added to 50.0 mL of the NaOH solution, what is the concentration of the resulting solution?

A. 1.25 M

Correct B. 1.50 M

C. 1.75 M

D. 2.00 M

Correct Answer: B

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Question 4

A 10.0 g sample of a metal is heated in a crucible until it decomposes completely. The mass of the metal obtained is 8.50 g. If the metal has a molar mass of 50.0 g/mol, calculate the percentage yield of the metal.

A. 85%

B. 90%

Correct C. 95%

D. 80%

Correct Answer: C

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Question 5

A 0.500 L sample of a gas at 25°C and 1.00 atm is allowed to expand to 1.50 L at cons\tant temperature. Calculate the work done by the gas.

Correct A. -0.750 L atm

B. -0.500 L atm

C. -1.00 L atm

D. -1.50 L atm

Correct Answer: A

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Question 6

Determine the number of moles of oxygen gas (O2) produced at STP when 2.5 moles of potassium chlorate (KClO3) decompose according to the equation: 2KClO3(s) → 2KCl(s) + 3O2(g).

A. 1.5 moles

B. 2.5 moles

Correct C. 3.75 moles

D. 4.5 moles

Correct Answer: C

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Question 7

A 0.500 M solution of HCl is mixed with 100.0 mL of 0.200 M solution of NaOH. What is the concentration of the resulting 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 8

A sample of a polymer has a molecular weight of 100,000 g/mol. If 2.5 g of the polymer is dissolved in 50 mL of solvent, what is the concentration of the solution in g/L?

A. 0.05 g/L

B. 0.10 g/L

Correct C. 0.20 g/L

D. 0.50 g/L

Correct Answer: C

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Question 9

A 1.0 L solution of 0.1 M NaCl is diluted to 2.0 L. What is the new concentration of the solution?

A. 0.05 M

Correct B. 0.10 M

C. 0.20 M

D. 0.50 M

Correct Answer: B

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Question 10

A 0.500 M solution of HCl is mixed with 100.0 mL of 0.200 M solution of NaOH. What is the concentration of the resulting 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 11

Determine the pH of a 0.1 M solution of HCl at 25°C, given that the dissociation cons\tant of HCl is 10^\( -7 \).

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 12

A 25 mL sample of 0.1 M NaOH is titrated with 0.1 M HCl. Calculate the pH of the solution after 10 mL of HCl has been added.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 13

The solubility of AgCl in water is 1.2 x 10^\( -5 \) M. Calculate the molar solubility of AgCl in a 0.1 M solution of NaCl.

Correct A. 1.2 x 10^\( -5 \)

B. 1.2 x 10^\( -4 \)

C. 1.2 x 10^\( -3 \)

D. 1.2 x 10^\( -2 \)

Correct Answer: A

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Question 14

A 10 mL sample of 0.1 M FeSO4 is electrolyzed at a cons\tant current of 1 A for 10 minutes. Calculate the mass of Fe deposited.

A. 0.1 g

Correct B. 0.2 g

C. 0.3 g

D. 0.4 g

Correct Answer: B

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Question 15

The rate cons\tant of a first-order reaction is 0.05 min^\( -1 \). Calculate the half-life of the reaction.

A. 10 min

Correct B. 20 min

C. 30 min

D. 40 min

Correct Answer: B

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Question 16

The reaction between sulfur dioxide and oxygen to form sulfur trioxide is highly exothermic. Calculate the s\tandard enthalpy change for the reaction: 2SO2(g) + O2(g) → 2SO3(g). The s\tandard enthalpy of formation of SO2(g) is -296 kJ/mol, and the s\tandard enthalpy of formation of SO3(g) is -395 kJ/mol.

Correct A. -799 kJ/mol

B. -699 kJ/mol

C. -899 kJ/mol

D. -899 kJ/mol

Correct Answer: A

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Question 17

A 2.5 M solution of HCl is mixed with a 1.0 M solution of NaOH. Calculate the concentration of the resulting solution after the reaction is complete.

A. 1.75 M

Correct B. 2.25 M

C. 2.5 M

D. 3.0 M

Correct Answer: B

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Question 18

The half-life of a radioactive subs\tance is 5.0 years. If the initial amount of the subs\tance is 100 g, what is the amount remaining after 15 years?

Correct A. 12.5 g

B. 25.0 g

C. 50.0 g

D. 75.0 g

Correct Answer: A

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Question 19

A solution containing 0.1 M HCl and 0.1 M NaOH is mixed with a solution containing 0.1 M H2SO4 and 0.1 M NaOH. What is the pH of the resulting solution?

A. 1.0

Correct B. 2.0

C. 3.0

D. 4.0

Correct Answer: B

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Question 20

The reaction between nitrogen and oxygen to form nitrogen dioxide is highly exothermic. Calculate the s\tandard enthalpy change for the reaction: N2(g) + O2(g) → 2NO2(g). The s\tandard enthalpy of formation of NO2(g) is -179 kJ/mol.

A. -179 kJ/mol

Correct B. -279 kJ/mol

C. -379 kJ/mol

D. -479 kJ/mol

Correct Answer: B

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Question 21

Determine the number of moles of oxygen gas (O2) required to react completely with 2.5 moles of carbon monoxide (CO) in the following reaction: 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 22

A 2.5 L flask contains 0.5 mol of an ideal gas at 300 K. Calculate the pressure of the gas u\sing the ideal gas law.

A. 1.2 atm

Correct B. 1.5 atm

C. 2.0 atm

D. 2.5 atm

Correct Answer: B

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Question 23

A metal (X) reacts with chlorine gas to form a white solid. The reaction is highly exothermic and releases 35.5 kJ of heat per mole of X. If 2.5 moles of X are reacted, how much heat is released?

Correct A. 87.5 kJ

B. 87.8 kJ

C. 88.0 kJ

D. 88.5 kJ

Correct Answer: A

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Question 24

A 0.5 M solution of sodium hydroxide (NaOH) is mixed with a 0.5 M solution of hydrochloric acid (HCl). What is the pH of the resulting solution?

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 25

A 2.5 L flask contains 0.5 mol of an ideal gas at 300 K. Calculate the number of molecules of the gas u\sing the ideal gas law.

A. 1.5 × 10^22

Correct B. 1.8 × 10^22

C. 2.0 × 10^22

D. 2.5 × 10^22

Correct Answer: B

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