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POST UTME AAUA 2018 Chemistry | Objective

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Question 1

Determine the number of moles of oxygen gas (O2) produced at STP when 2.5 moles of hydrogen gas (H2) react with excess oxygen gas according to the equation: 2H2 + O2 → 2H2O.

A. 1.25 moles

B. 2.5 moles

Correct C. 5.0 moles

D. 6.25 moles

Correct Answer: C

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Question 2

A 10.0 mL sample of a solution containing 0.25 M NaCl is diluted to a total volume of 50.0 mL. What is the concentration of the resulting solution?

A. 0.005 M

B. 0.01 M

Correct C. 0.05 M

D. 0.1 M

Correct Answer: C

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Question 3

A 2.0 g sample of a non-metallic element is heated in a crucible until it reaches a temperature of 2500°C. What is the mass of the element that has sublimed?

A. 1.5 g

Correct B. 1.8 g

C. 2.0 g

D. 2.2 g

Correct Answer: B

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Question 4

A 1.0 L sample of a 0.1 M solution of a weak acid (HA) is titrated with 0.1 M NaOH. What is the pH of the solution after the addition of 20.0 mL of NaOH?

A. 2.0

B. 3.0

Correct C. 4.0

D. 5.0

Correct Answer: C

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Question 5

A 5.0 g sample of a hydrocarbon \( C_xH_y \) is burned in a combustion tube, producing 10.0 mL of CO2 and 15.0 mL of H2O. What is the empirical formula of the hydrocarbon?

A. C2H6

B. C3H8

Correct C. C4H10

D. C5H12

Correct Answer: C

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Question 6

Determine the pH of a solution containing 0.1 M HCl and 0.1 M NaOH.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 7

A 2.5 L flask contains 0.5 mol of an ideal gas at 298 K. Calculate the pressure of the gas.

A. 1.5 atm

Correct B. 2.5 atm

C. 3.5 atm

D. 4.5 atm

Correct Answer: B

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Question 8

A solution contains 0.1 M HCl and 0.1 M NaOH. What is the pH of the solution?

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 9

A 2.5 L flask contains 0.5 mol of an ideal gas at 298 K. Calculate the pressure of the gas.

A. 1.5 atm

Correct B. 2.5 atm

C. 3.5 atm

D. 4.5 atm

Correct Answer: B

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Question 10

A solution contains 0.1 M HCl and 0.1 M NaOH. What is the pH of the solution?

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 11

A 0.500 g sample of a metal carbonate is heated to produce a 0.250 g sample of the metal oxide. What is the percentage yield of the metal oxide if the theoretical yield is 0.300 g?

Correct A. 75%

B. 80%

C. 85%

D. 90%

Correct Answer: A

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Question 12

A solution contains 0.0500 M HCl and 0.0500 M NaOH. What is the concentration of the resulting solution after the reaction is complete?

A. 0.0500 M

Correct B. 0.100 M

C. 0.150 M

D. 0.200 M

Correct Answer: B

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Question 13

A 2.50 g sample of a metal hydroxide is dissolved in water to produce a solution with a pH of 10.50. What is the concentration of the metal ion in the solution?

A. 0.100 M

B. 0.150 M

Correct C. 0.200 M

D. 0.250 M

Correct Answer: C

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Question 14

A 1.00 g sample of a metal carbonate is heated to produce a 0.500 g sample of the metal oxide. What is the percentage yield of the metal oxide if the theoretical yield is 0.600 g?

A. 80%

Correct B. 85%

C. 90%

D. 95%

Correct Answer: B

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Question 15

A solution contains 0.0500 M HCl and 0.0500 M NaOH. What is the concentration of the resulting solution after the reaction is complete?

A. 0.0500 M

Correct B. 0.100 M

C. 0.150 M

D. 0.200 M

Correct Answer: B

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Question 16

Calculate the s\tandard enthalpy change (ΔH°) for the reaction: 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s). Given that the s\tandard enthalpy of formation (ΔHf°) for Al2O3(s) is -1675.7 kJ/mol, and the s\tandard enthalpy of formation for Fe2O3(s) is -826.4 kJ/mol.

Correct A. -1031.1 kJ/mol

B. -1031.2 kJ/mol

C. -1031.3 kJ/mol

D. -1031.4 kJ/mol

Correct Answer: A

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Question 17

A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the pH of the solution after the addition of 25.0 mL of NaOH.

A. 2.00

Correct B. 2.50

C. 3.00

D. 3.50

Correct Answer: B

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Question 18

The atomic radius of an element is 100 pm. If the element has a valence electron configuration of 3s^2 3p^6, what is the expected oxidation state of the element?

A. +2

B. +3

C. +4

Correct D. +5

Correct Answer: D

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Question 19

A 2.00 g sample of an unknown hydrocarbon is burned in a combustion calorimeter. The heat of combustion is -3930 kJ/mol. Calculate the molar mass of the hydrocarbon.

A. 50.0 g/mol

B. 60.0 g/mol

Correct C. 70.0 g/mol

D. 80.0 g/mol

Correct Answer: C

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Question 20

The s\tandard enthalpy of formation (ΔHf°) for CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation for C(s) u\sing the following reaction: C(s) + O2(g) → CO2(g).

A. -393.5 kJ/mol

Correct B. +393.5 kJ/mol

C. -393.0 kJ/mol

D. +393.0 kJ/mol

Correct Answer: B

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Question 21

The reaction of zinc metal with copper(II) sulfate solution is represented by the equation: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s). If 2.50 g of zinc metal is added to 100 mL of 0.100 M copper(II) sulfate solution, what is the limiting reac\tant?

A. Zn(s)

Correct B. CuSO4(aq)

C. ZnSO4(aq)

D. Cu(s)

Correct Answer: B

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Question 22

A sample of oxygen gas occupies a volume of 2.50 L at a pressure of 1.00 atm and a temperature of 298 K. What is the number of moles of oxygen gas present in the sample?

Correct A. 1.00 mol

B. 2.00 mol

C. 3.00 mol

D. 4.00 mol

Correct Answer: A

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Question 23

The s\tandard reduction potential of the zinc/zinc ion couple is -0.76 V. What is the s\tandard cell potential for a cell consisting of a zinc anode and a copper cathode?

A. -0.76 V

Correct B. -0.44 V

C. -0.24 V

D. -0.14 V

Correct Answer: B

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Question 24

A solution containing 0.100 M sodium chloride is mixed with a solution containing 0.100 M silver nitrate. What is the concentration of chloride ions in the resulting solution?

Correct A. 0.0500 M

B. 0.100 M

C. 0.150 M

D. 0.200 M

Correct Answer: A

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Question 25

The reaction of hydrogen gas with oxygen gas is represented by the equation: 2H2(g) + O2(g) → 2H2O(l). What is the balanced equation for the reaction of hydrogen gas with oxygen gas in the presence of a catalyst?

Correct A. 2H2(g) + O2(g) → 2H2O(l)

B. H2(g) + O2(g) → H2O(l)

C. 2H2(g) + O2(g) → 4H2O(l)

D. H2(g) + O2(g) → 2H2O(l)

Correct Answer: A

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