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POST UTME ACHIEVERS UNIVERSITY 2017 Chemistry | Objective

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Question 1

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of combustion of 1.5 mol of C(s) to form CO2(g).

A. -589.25 kJ

B. -589.25 kJ

C. -589.25 kJ

Correct D. -589.25 kJ

Correct Answer: D

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Question 2

A 0.5 M solution of HCl is mixed with a 0.5 M solution of NaOH. The reaction is carried out in a calorimeter. If the temperature of the solution increases by 5°C, what is the value of ΔH for the reaction?

A. -50 kJ

B. -50 kJ

C. -50 kJ

Correct D. -50 kJ

Correct Answer: D

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Question 3

The s\tandard enthalpy of formation of H2O(l) is -285.8 kJ/mol. Calculate the s\tandard enthalpy of vaporization of 1 mol of H2O(l) at 100°C.

A. -44.0 kJ

B. -44.0 kJ

C. -44.0 kJ

Correct D. -44.0 kJ

Correct Answer: D

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Question 4

A 0.5 M solution of HCl is mixed with a 0.5 M solution of NaOH. The reaction is carried out in a calorimeter. If the temperature of the solution increases by 5°C, what is the value of ΔS for the reaction?

A. -50 J/K

B. -50 J/K

C. -50 J/K

Correct D. -50 J/K

Correct Answer: D

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Question 5

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of combustion of 1.5 mol of C(s) to form CO2(g).

A. -589.25 kJ

B. -589.25 kJ

C. -589.25 kJ

Correct D. -589.25 kJ

Correct Answer: D

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Question 6

A 2.50 g sample of a metal carbonate is heated to produce a metal oxide and carbon dioxide gas. If the mass of the metal oxide produced is 1.75 g, calculate the percentage yield of the metal oxide.

A. 85%

B. 90%

C. 95%

Correct D. 92%

Correct Answer: D

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Question 7

The reaction between sodium hydroxide and hydrochloric acid is represented by the equation: 2NaOH + HCl -> NaCl + 2H2O. If 25.0 cm^3 of 0.100 M NaOH is mixed with 25.0 cm^3 of 0.100 M HCl, calculate the number of moles of NaCl produced.

A. 0.005 mol

Correct B. 0.010 mol

C. 0.015 mol

D. 0.020 mol

Correct Answer: B

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Question 8

The enthalpy change (ΔH) for the reaction: 2H2(g) + O2(g) -> 2H2O(l) is -572 kJ/mol. Calculate the enthalpy change for the reaction: H2(g) + 1/2O2(g) -> H2O(l).

Correct A. -286 kJ/mol

B. -572 kJ/mol

C. -858 kJ/mol

D. -1143 kJ/mol

Correct Answer: A

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Question 9

A 10.0 g sample of a metal hydroxide is dissolved in water to produce a solution with a pH of 10.5. Calculate the concentration of the metal hydroxide.

A. 0.0010 M

B. 0.010 M

Correct C. 0.100 M

D. 1.00 M

Correct Answer: C

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Question 10

A 25.0 cm^3 sample of a solution containing 0.100 M NaCl is mixed with 25.0 cm^3 of water. Calculate the concentration of the resulting solution.

A. 0.010 M

Correct B. 0.020 M

C. 0.030 M

D. 0.040 M

Correct Answer: B

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Question 11

A polymer is a large molecule composed of many repeated subunits called monomers. Which of the following is an example of a polymer?

A. DNA

B. Protein

C. Starch

Correct D. Cellulose

Correct Answer: D

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Question 12

The atomic radius of an element is the dis\tance from the nucleus to the outermost electron. Which of the following elements has the largest atomic radius?

A. Lithium

B. Sodium

C. Potassium

Correct D. Rubidium

Correct Answer: D

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Question 13

The periodic table is arranged in a way that elements with similar properties are placed in the same group. Which of the following elements is in the same group as Carbon?

A. Nitrogen

B. Oxygen

C. Fluorine

Correct D. Boron

Correct Answer: D

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Question 14

The environmental impact of a chemical reaction can be determined by its Gibbs free energy change. Which of the following reactions has a negative Gibbs free energy change?

Correct A. 2H2 + O2 → 2H2O

B. 2H2 + O2 → 2H2O2

C. 2H2 + O2 → 2H2O2

D. 2H2 + O2 → 2H2O

Correct Answer: A

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Question 15

The structure of a biomolecule can be determined by its X-ray crystal\lography. Which of the following biomolecules has a helical structure?

Correct A. DNA

B. Protein

C. Starch

D. Cellulose

Correct Answer: A

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Question 16

The reaction between zinc metal and copper(II) sulfate solution is represented by the equation: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s). What is the oxidation state of copper in the product Cu(s)?

A. 0

B. +1

Correct C. +2

D. -1

Correct Answer: C

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Question 17

A 2.5 M solution of sodium hydroxide (NaOH) is prepared by dissolving 12.5 g of NaOH in 1 L of water. What is the molarity of the solution?

A. 2.0 M

Correct B. 2.5 M

C. 3.0 M

D. 3.5 M

Correct Answer: B

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Question 18

The diagram below shows a titration setup.

A. The burette contains the acid.

B. The beaker contains the acid.

Correct C. The burette contains the base.

D. The beaker contains the base.

Correct Answer: C

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Question 19

The reaction between hydrogen gas and chlorine gas is represented by the equation: H2(g) + Cl2(g) → 2HCl(g). What is the limiting reac\tant if 2.0 g of H2 is reacted with 3.0 g of Cl2?

Correct A. H2

B. Cl2

C. Neither

D. Both

Correct Answer: A

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Question 20

The diagram below shows a molecular structure.

A. The molecule is polar.

Correct B. The molecule is nonpolar.

C. The molecule is ionic.

D. The molecule is covalent.

Correct Answer: B

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Question 21

The electrolysis of a solution of copper(II) sulfate u\sing a copper electrode results in the formation of copper metal at the cathode. Write the half-equation for the reduction reaction at the cathode.

A. Cu²⁺ + 2e⁻ → Cu

B. Cu + 2e⁻ → Cu²⁺

Correct C. Cu²⁺ + 2e⁻ → Cu

D. Cu + 2e⁻ → Cu²⁺

Correct Answer: C

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Question 22

A solution of sodium hydroxide is titrated with a solution of hydrochloric acid. The pH of the solution at the equivalence point is 7.

A. NaOH + HCl → NaCl + H₂O

Correct B. NaOH + HCl → NaCl + H₂O

C. NaOH + HCl → NaCl + H₂O

D. NaOH + HCl → NaCl + H₂O

Correct Answer: B

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Question 23

A colloidal solution of gold is prepared by the reduction of gold chloride with sodium citrate. The resulting particles have a diameter of 10 nm.

A. AuCl₃ + 3NaC₆H₅O₇ → Au + 3NaCl + 3C₆H₅O₇

B. AuCl₃ + 3NaC₆H₅O₇ → Au + 3NaCl + 3C₆H₅O₇

Correct C. AuCl₃ + 3NaC₆H₅O₇ → Au + 3NaCl + 3C₆H₅O₇

D. AuCl₃ + 3NaC₆H₅O₇ → Au + 3NaCl + 3C₆H₅O₇

Correct Answer: C

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Question 24

A sample of a gas is collected over water at a temperature of 25°C and a pressure of 1 atm. The partial pressure of the gas is 0.8 atm.

A. PV = nRT

Correct B. PV = nRT

C. PV = nRT

D. PV = nRT

Correct Answer: B

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Question 25

A solution of sodium chloride is electrolyzed u\sing a copper electrode. The anode reaction is:

A. 2Cl⁻ → Cl₂ + 2e⁻

Correct B. 2Cl⁻ → Cl₂ + 2e⁻

C. 2Cl⁻ → Cl₂ + 2e⁻

D. 2Cl⁻ → Cl₂ + 2e⁻

Correct Answer: B

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