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POST UTME CRAWFORD UNIVERSITY 2023 Chemistry | Objective

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Question 1

A 2.50 L flask contains 0.500 mol of an ideal gas at 298 K. Calculate the pressure of the gas in atm.

Correct A. 1.01 atm

B. 2.02 atm

C. 3.03 atm

D. 4.04 atm

Correct Answer: A

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Question 2

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of H2O(l) from the following reaction: CO(g) + H2(g) → H2O(l) + C(s).

A. -241.8 kJ/mol

Correct B. -285.8 kJ/mol

C. -393.5 kJ/mol

D. -418.8 kJ/mol

Correct Answer: B

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Question 3

A 0.100 M solution of NaCl is electrolyzed u\sing a current of 0.500 A for 2.00 h. Calculate the mass of Cl2(g) produced.

A. 0.0100 g

Correct B. 0.0200 g

C. 0.0300 g

D. 0.0400 g

Correct Answer: B

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Question 4

A 0.100 M solution of AgNO3 is mixed with a 0.100 M solution of NaCl. Calculate the concentration of AgCl(s) that precipitates.

A. 0.0100 M

Correct B. 0.0200 M

C. 0.0300 M

D. 0.0400 M

Correct Answer: B

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Question 5

A 2.00 L flask contains 0.500 mol of an ideal gas at 298 K. Calculate the pressure of the gas in atm.

Correct A. 1.01 atm

B. 2.02 atm

C. 3.03 atm

D. 4.04 atm

Correct Answer: A

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Question 6

A 2.5 g sample of a non-metallic oxide of nitrogen is heated in a stream of hydrogen gas at 1273 K. The resulting gas is passed through a solution of sodium hydroxide, and the volume of the gas collected at room temperature and pressure is 2.5 liters. What is the empirical formula of the oxide?

Correct A. N2O

B. NO

C. N2O3

D. N2O5

Correct Answer: A

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Question 7

A 0.5 M solution of a strong acid is titrated with 0.5 M NaOH. The pH of the solution at the equivalence point is 7. What is the pKa of the acid?

Correct A. 1

B. 2

C. 3

D. 4

Correct Answer: A

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Question 8

A 2.0 g sample of a metal carbonate is heated in a stream of carbon dioxide gas at 1273 K. The resulting gas is passed through a solution of sodium hydroxide, and the volume of the gas collected at room temperature and pressure is 2.5 liters. What is the empirical formula of the metal carbonate?

Correct A. CaCO3

B. MgCO3

C. FeCO3

D. CuCO3

Correct Answer: A

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Question 9

A 0.5 M solution of a weak acid is titrated with 0.5 M NaOH. The pH of the solution at the equivalence point is 7. What is the pKa of the acid?

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 10

A 2.0 g sample of a metal oxide is heated in a stream of hydrogen gas at 1273 K. The resulting gas is passed through a solution of sodium hydroxide, and the volume of the gas collected at room temperature and pressure is 2.5 liters. What is the empirical formula of the metal oxide?

Correct A. FeO

B. CuO

C. MgO

D. CaO

Correct Answer: A

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Question 11

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) at the same temperature.

A. 1.8 × 10^\( -2 \) atm

Correct B. 3.6 × 10^\( -2 \) atm

C. 1.8 × 10^\( -1 \) atm

D. 3.6 × 10^\( -1 \) atm

Correct Answer: B

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Question 12

A 2.50-g sample of a compound containing only carbon and hydrogen is analyzed by combustion. The amount of CO2 produced is 1.25 g, and the amount of H2O produced is 0.75 g. What is the empirical formula of the compound?

A. CH2

B. C2H4

Correct C. C2H6

D. C3H8

Correct Answer: C

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Question 13

A 10.0-mL sample of a solution containing 0.500 M HCl is titrated with 0.500 M NaOH. What is the pH of the solution after the titration is complete?

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 14

A 5.00-g sample of a metal is heated in a crucible until it is completely oxidized. The mass of the crucible and the oxide is 10.5 g. What is the identity of the metal?

A. Al

Correct B. Fe

C. Cu

D. Zn

Correct Answer: B

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Question 15

A 2.00-L sample of a gas at 25°C and 1.00 atm is compressed to 2.00 atm at cons\tant temperature. What is the new volume of the gas?

A. 1.00 L

Correct B. 2.00 L

C. 3.00 L

D. 4.00 L

Correct Answer: B

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Question 16

Calculate the s\tandard enthalpy of formation of CO2(g) from the following data: ΔHf(CO2(g)) = ?, ΔHf(C) = -393.5 kJ/mol, ΔHf(O2(g)) = 0 kJ/mol.

A. -393.5 kJ/mol

B. 0 kJ/mol

Correct C. 393.5 kJ/mol

D. 0 kJ/mol

Correct Answer: C

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Question 17

A 2.50 M solution of HCl is mixed with a 1.00 M solution of NaOH. Calculate the concentration of the resulting solution.

Correct A. 1.25 M

B. 2.50 M

C. 3.75 M

D. 4.00 M

Correct Answer: A

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Question 18

A metal M has a density of 9.0 g/cm^3 and a molar mass of 60.0 g/mol. Calculate the volume of 1.00 mol of M.

Correct A. 1.67 cm^3

B. 2.00 cm^3

C. 3.33 cm^3

D. 4.00 cm^3

Correct Answer: A

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Question 19

A 1.00 M solution of H2SO4 is mixed with a 1.00 M solution of NaOH. Calculate the concentration of the resulting solution.

A. 0.50 M

B. 1.00 M

Correct C. 1.50 M

D. 2.00 M

Correct Answer: C

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Question 20

A metal M has a density of 10.0 g/cm^3 and a molar mass of 80.0 g/mol. Calculate the volume of 1.00 mol of M.

A. 2.00 cm^3

Correct B. 2.50 cm^3

C. 3.33 cm^3

D. 4.00 cm^3

Correct Answer: B

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Question 21

A 2.0 M solution of NaOH is mixed with a 2.0 M solution of HCl. If the initial temperature of the NaOH solution is 25°C and the initial temperature of the HCl solution is 20°C, what is the final temperature of the mixture after the reaction is complete?

A. 25°C

B. 20°C

Correct C. 22.5°C

D. 30°C

Correct Answer: C

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Question 22

The polymerization of styrene \( C6H5CH=CH2 \) to form polystyrene involves the addition of a monomer unit to the growing polymer chain. Which of the following is the correct representation of the initiation step in the polymerization reaction?

Correct A. C6H5CH=CH2 + M^- \rightarrow C6H5CH(CH3)CH2^-

B. C6H5CH=CH2 + M^- \rightarrow C6H5CH2CH3

C. C6H5CH=CH2 + M^- \rightarrow C6H5CH=CHM^+

D. C6H5CH=CH2 + M^- \rightarrow C6H5CH2CH2M^+

Correct Answer: A

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Question 23

A sample of a gas at 25°C and 1 atm is found to have a volume of 2.5 L. What is the number of moles of the gas present in the sample?

A. 0.05 mol

Correct B. 0.1 mol

C. 0.2 mol

D. 0.5 mol

Correct Answer: B

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Question 24

The reaction between hydrogen peroxide (H2O2) and potassium iodide (KI) is a first-order reaction with respect to H2O2. If the initial concentration of H2O2 is 0.1 M and the rate cons\tant (k) is 0.05 min^-1, what is the concentration of H2O2 after 10 minutes?

A. 0.01 M

Correct B. 0.02 M

C. 0.03 M

D. 0.04 M

Correct Answer: B

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Question 25

The element with atomic number 12 is _______.

A. Mg

Correct B. Ca

C. Sr

D. Ba

Correct Answer: B

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