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POST UTME ABU 2017 Chemistry | Objective

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Question 1

Determine the oxidation state of the metal ion in the complex [Cr(H2O)6]Cl3.

Correct A. +3

B. +2

C. +1

D. +6

Correct Answer: A

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Question 2

A 0.5 M solution of NaOH is mixed with a 0.5 M solution of HCl. What is the pH of the resulting solution?

Correct A. 7

B. 8

C. 9

D. 10

Correct Answer: A

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Question 3

The diagram below shows a titration setup. What is the purpose of the burette?

A. To measure the volume of the acid

Correct B. To measure the volume of the base

C. To mix the acid and base

D. To measure the pH of the solution

Correct Answer: B

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Question 4

A 1.0 M solution of H2SO4 is mixed with a 1.0 M solution of NaOH. What is the resulting solution?

Correct A. Na2SO4

B. H2O

C. NaHSO4

D. H2SO4

Correct Answer: A

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Question 5

The diagram below shows a circuit. What is the purpose of the resistor?

Correct A. To reduce the current

B. To increase the voltage

C. To measure the resis\tance

D. To measure the current

Correct Answer: A

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Question 6

The energy change (ΔE) for a reaction is given by ΔE = ΔH - TΔS. If ΔH = 50 kJ/mol and ΔS = 0.1 kJ/mol·K, calculate ΔE at 298 K.

Correct A. 40 kJ/mol

B. 50 kJ/mol

C. 60 kJ/mol

D. 70 kJ/mol

Correct Answer: A

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Question 7

A 0.1 M solution of NaOH is titrated with 0.1 M HCl. If 25 mL of HCl is required to reach the equivalence point, calculate the number of moles of NaOH.

Correct A. 0.0025 mol

B. 0.005 mol

C. 0.0075 mol

D. 0.01 mol

Correct Answer: A

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Question 8

The s\tandard electrode potential (E°) for the reaction 2Ag+ + 2e- → Ag is 0.80 V. Calculate the s\tandard Gibbs free energy change (ΔG°) for this reaction.

Correct A. -1.6 kJ/mol

B. -3.2 kJ/mol

C. -4.8 kJ/mol

D. -6.4 kJ/mol

Correct Answer: A

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Question 9

A 1.0 M solution of H2SO4 is titrated with 1.0 M NaOH. If 20 mL of NaOH is required to reach the equivalence point, calculate the number of moles of H2SO4.

Correct A. 0.01 mol

B. 0.02 mol

C. 0.03 mol

D. 0.04 mol

Correct Answer: A

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Question 10

The s\tandard enthalpy change (ΔH°) for the reaction 2H2 + O2 → 2H2O is 572 kJ/mol. Calculate the s\tandard entropy change (ΔS°) for this reaction.

Correct A. -1.9 kJ/mol·K

B. -2.1 kJ/mol·K

C. -2.3 kJ/mol·K

D. -2.5 kJ/mol·K

Correct Answer: A

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Question 11

Determine the number of moles of oxygen gas (O2) that will react with 2.5 moles of carbon monoxide (CO) according to the balanced equation: 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 12

A sample of nitrogen gas (N2) is collected over water at a temperature of 25°C and a pressure of 1 atm. If the partial pressure of water vapor is 0.02 atm, what is the mole \fraction of nitrogen gas?

A. 0.98

B. 0.99

Correct C. 0.995

D. 0.999

Correct Answer: C

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Question 13

A solution contains 0.5 M HCl and 0.2 M NaOH. What is the pH of the solution after mixing 50 mL of each solution?

A. 1.0

Correct B. 2.0

C. 3.0

D. 4.0

Correct Answer: B

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Question 14

A metal (X) reacts with hydrochloric acid (HCl) to produce hydrogen gas (H2) and a salt. The reaction is: X + 2HCl → H2 + 2ClX. If 2.5 g of X reacts with 10 mL of 1 M HCl, what is the molar mass of X?

A. 50 g/mol

B. 75 g/mol

Correct C. 100 g/mol

D. 150 g/mol

Correct Answer: C

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Question 15

A solution contains 0.1 M H2SO4 and 0.2 M NaOH. What is the pH of the solution after mixing 50 mL of each solution?

A. 1.0

B. 2.0

Correct C. 3.0

D. 4.0

Correct Answer: C

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Question 16

Determine the number of moles of carbon dioxide produced when 2.50 g of calcium carbonate is heated in a crucible.

A. 0.050 mol

Correct B. 0.100 mol

C. 0.150 mol

D. 0.200 mol

Correct Answer: B

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Question 17

A 2.00 L flask contains 0.500 mol of an ideal gas at 25°C. What is the pressure of the gas?

A. 1.00 atm

Correct B. 2.00 atm

C. 3.00 atm

D. 4.00 atm

Correct Answer: B

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Question 18

A solution of 0.100 M NaCl is prepared by dissolving 0.0100 mol of NaCl in 1.00 L of water. What is the concentration of Cl^- ions in the solution?

A. 0.050 M

Correct B. 0.100 M

C. 0.150 M

D. 0.200 M

Correct Answer: B

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Question 19

A 0.500 L flask contains 0.200 mol of O2 gas at 25°C. What is the partial pressure of O2?

A. 0.50 atm

Correct B. 1.00 atm

C. 1.50 atm

D. 2.00 atm

Correct Answer: B

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Question 20

A 1.00 L flask contains 0.500 mol of an ideal gas at 25°C. What is the volume of the gas at 50°C?

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 21

The molar mass of a compound is 100 g/mol. If 2.5 g of the compound is dissolved in 25 mL of water, what is the concentration of the solution in terms of molarity?

A. 0.1 M

B. 0.2 M

Correct C. 0.5 M

D. 1 M

Correct Answer: C

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Question 22

A 2.0 M solution of HCl is prepared by dissolving 36.5 g of HCl in 1.0 L of water. What is the pH of the solution?

A. 0.5

B. 1.0

C. 1.5

Correct D. 2.0

Correct Answer: D

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Question 23

A sample of CO2 gas has a volume of 2.5 L at a pressure of 1.0 atm and a temperature of 25°C. What is the volume of the gas at a pressure of 2.0 atm and a temperature of 50°C?

A. 1.5 L

B. 2.0 L

Correct C. 2.5 L

D. 3.0 L

Correct Answer: C

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Question 24

A 1.0 M solution of NaOH is prepared by dissolving 40.0 g of NaOH in 1.0 L of water. What is the concentration of the solution in terms of molarity?

A. 0.5 M

Correct B. 1.0 M

C. 1.5 M

D. 2.0 M

Correct Answer: B

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Question 25

A sample of H2 gas has a volume of 1.0 L at a pressure of 1.0 atm and a temperature of 25°C. What is the volume of the gas at a pressure of 2.0 atm and a temperature of 50°C?

A. 0.5 L

Correct B. 1.0 L

C. 1.5 L

D. 2.0 L

Correct Answer: B

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