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POST UTME BABCOCK UNIVERSITY 2020 Chemistry | Objective

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Question 1

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. Assume the reaction is: CaO(s) + CO2(g) → CaCO3(s).

Correct A. -1781.6 kJ/mol

B. -1781.7 kJ/mol

C. -1781.8 kJ/mol

D. -1781.9 kJ/mol

Correct Answer: A

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Question 2

A metal M has an atomic radius of 135 pm and an electron configuration of [Ar] 4s2 3d5. Which of the following is a possible oxidation state of M?

A. +2

Correct B. +3

C. +4

D. +5

Correct Answer: B

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Question 3

The reaction of 2.50 g of a hydrocarbon with 50.0 mL of O2(g) at STP produces 3.00 g of CO2(g). What is the empirical formula of the hydrocarbon?

Correct A. C2H4

B. C3H6

C. C4H8

D. C5H10

Correct Answer: A

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Question 4

A solution of 0.100 M NaOH is titrated with 0.100 M HCl. What is the pH of the solution after 25.0 mL of HCl has been added?

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 5

A 1.00 L solution of 0.100 M CaCl2 is mixed with 1.00 L of 0.100 M Na2SO4. What is the concentration of Ca2+ ions in the resulting solution?

Correct A. 0.0500 M

B. 0.0501 M

C. 0.0502 M

D. 0.0503 M

Correct Answer: A

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Question 6

Calculate the molar mass of a compound that contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. The atomic masses of carbon, hydrogen, and oxygen are 12.01 g/mol, 1.008 g/mol, and 16.00 g/mol, respectively.

A. 48.0 g/mol

Correct B. 52.0 g/mol

C. 56.0 g/mol

D. 60.0 g/mol

Correct Answer: B

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Question 7

A 2.50 M solution of HCl is mixed with a 1.25 M solution of NaOH. Calculate the pH of the resulting solution after the reaction is complete.

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 8

A sample of a gas occupies 2.50 L at a pressure of 1.50 atm. If the temperature is increased to 25°C, what is the new volume of the gas?

A. 3.00 L

B. 4.00 L

Correct C. 5.00 L

D. 6.00 L

Correct Answer: C

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Question 9

A 0.500 M solution of NaOH is mixed with a 0.250 M solution of HCl. Calculate the concentration of the resulting solution after the reaction is complete.

A. 0.125 M

Correct B. 0.250 M

C. 0.375 M

D. 0.500 M

Correct Answer: B

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Question 10

A 1.00 M solution of HCl is mixed with a 0.500 M solution of NaOH. Calculate the pH of the resulting solution after the reaction is complete.

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 11

Determine the number of moles of oxygen gas (O2) produced at s\tandard temperature and pressure (STP) when 2.50 g of potassium chlorate (KClO3) is decomposed according to the equation: 2KClO3(s) → 2KCl(s) + 3O2(g).

A. 0.0500 mol

Correct B. 0.100 mol

C. 0.150 mol

D. 0.200 mol

Correct Answer: B

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Question 12

A 2.00 L flask contains 0.500 atm of an ideal gas at 298 K. What is the pressure of the gas in the flask at 323 K?

A. 0.400 atm

B. 0.500 atm

Correct C. 0.600 atm

D. 0.700 atm

Correct Answer: C

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Question 13

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

Correct A. -110.5 kJ/mol

B. -130.5 kJ/mol

C. -150.5 kJ/mol

D. -170.5 kJ/mol

Correct Answer: A

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Question 14

A 10.0 g sample of a metal (M) is dissolved in 50.0 mL of 1.00 M HCl. The resulting solution is then titrated with 0.100 M NaOH. If 25.0 mL of NaOH is required to reach the equivalence point, what is the identity of the metal?

A. Zn

Correct B. Fe

C. Cu

D. Ag

Correct Answer: B

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Question 15

A 2.00 L flask contains 0.500 atm of an ideal gas at 298 K. What is the volume of the gas in the flask at 323 K?

A. 1.50 L

B. 1.75 L

Correct C. 2.00 L

D. 2.25 L

Correct Answer: C

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Question 16

Determine the pH of a 0.1 M solution of HCl.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 17

A 25 mL sample of 0.5 M H2SO4 is titrated with 1 M NaOH. Calculate the volume of NaOH required to reach the equivalence point.

A. 12.5 mL

B. 25 mL

Correct C. 37.5 mL

D. 50 mL

Correct Answer: C

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Question 18

The s\tandard electrode potential of the Zn2+/Zn couple is -0.76 V. Calculate the s\tandard electrode potential of the Cu2+/Cu couple if the s\tandard electrode potential of the Cu2+/Cu couple is -0.34 V.

A. -0.10 V

B. -0.20 V

C. -0.30 V

Correct D. -0.40 V

Correct Answer: D

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Question 19

A polymer has a molecular weight of 100,000 g/mol and a degree of polymerization of 500. Calculate the molar mass of the repeating unit.

A. 100 g/mol

B. 200 g/mol

Correct C. 500 g/mol

D. 1000 g/mol

Correct Answer: C

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Question 20

The half-life of a radioactive subs\tance is 10 years. If the initial activity is 1000 Bq, calculate the activity after 20 years.

A. 100 Bq

Correct B. 500 Bq

C. 1000 Bq

D. 2000 Bq

Correct Answer: B

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Question 21

A 2.5 M solution of HCl is prepared by dissolving 25 g of HCl in 1000 mL of water. Calculate the number of moles of HCl in the solution.

A. 0.1 mol

Correct B. 0.2 mol

C. 0.5 mol

D. 1.0 mol

Correct Answer: B

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Question 22

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of CH4(g) from the following reaction: C(s) + 2H2(g) → CH4(g).

Correct A. -74.8 kJ/mol

B. -74.5 kJ/mol

C. -74.2 kJ/mol

D. -75.1 kJ/mol

Correct Answer: A

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Question 23

A 1.0 M solution of NaOH is prepared by dissolving 40 g of NaOH in 1000 mL of water. Calculate the pH of the solution.

A. 13.0

Correct B. 12.0

C. 11.0

D. 10.0

Correct Answer: B

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Question 24

A 2.0 M solution of H2SO4 is prepared by dissolving 80 g of H2SO4 in 1000 mL of water. Calculate the number of moles of H2SO4 in the solution.

A. 0.4 mol

Correct B. 0.8 mol

C. 1.2 mol

D. 1.6 mol

Correct Answer: B

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Question 25

The s\tandard enthalpy of formation of H2O(l) is -285.8 kJ/mol. Calculate the s\tandard enthalpy of formation of CO2(g) from the following reaction: C(s) + O2(g) → CO2(g).

Correct A. -393.5 kJ/mol

B. -393.2 kJ/mol

C. -393.8 kJ/mol

D. -393.1 kJ/mol

Correct Answer: A

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