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Chemistry: Atoms First

Exercises

Chemistry: Atoms FirstExercises
  1. Preface
  2. 1 Essential Ideas
    1. Introduction
    2. 1.1 Chemistry in Context
    3. 1.2 Phases and Classification of Matter
    4. 1.3 Physical and Chemical Properties
    5. 1.4 Measurements
    6. 1.5 Measurement Uncertainty, Accuracy, and Precision
    7. 1.6 Mathematical Treatment of Measurement Results
    8. Key Terms
    9. Key Equations
    10. Summary
    11. Exercises
  3. 2 Atoms, Molecules, and Ions
    1. Introduction
    2. 2.1 Early Ideas in Atomic Theory
    3. 2.2 Evolution of Atomic Theory
    4. 2.3 Atomic Structure and Symbolism
    5. 2.4 Chemical Formulas
    6. Key Terms
    7. Key Equations
    8. Summary
    9. Exercises
  4. 3 Electronic Structure and Periodic Properties of Elements
    1. Introduction
    2. 3.1 Electromagnetic Energy
    3. 3.2 The Bohr Model
    4. 3.3 Development of Quantum Theory
    5. 3.4 Electronic Structure of Atoms (Electron Configurations)
    6. 3.5 Periodic Variations in Element Properties
    7. 3.6 The Periodic Table
    8. 3.7 Molecular and Ionic Compounds
    9. Key Terms
    10. Key Equations
    11. Summary
    12. Exercises
  5. 4 Chemical Bonding and Molecular Geometry
    1. Introduction
    2. 4.1 Ionic Bonding
    3. 4.2 Covalent Bonding
    4. 4.3 Chemical Nomenclature
    5. 4.4 Lewis Symbols and Structures
    6. 4.5 Formal Charges and Resonance
    7. 4.6 Molecular Structure and Polarity
    8. Key Terms
    9. Key Equations
    10. Summary
    11. Exercises
  6. 5 Advanced Theories of Bonding
    1. Introduction
    2. 5.1 Valence Bond Theory
    3. 5.2 Hybrid Atomic Orbitals
    4. 5.3 Multiple Bonds
    5. 5.4 Molecular Orbital Theory
    6. Key Terms
    7. Key Equations
    8. Summary
    9. Exercises
  7. 6 Composition of Substances and Solutions
    1. Introduction
    2. 6.1 Formula Mass and the Mole Concept
    3. 6.2 Determining Empirical and Molecular Formulas
    4. 6.3 Molarity
    5. 6.4 Other Units for Solution Concentrations
    6. Key Terms
    7. Key Equations
    8. Summary
    9. Exercises
  8. 7 Stoichiometry of Chemical Reactions
    1. Introduction
    2. 7.1 Writing and Balancing Chemical Equations
    3. 7.2 Classifying Chemical Reactions
    4. 7.3 Reaction Stoichiometry
    5. 7.4 Reaction Yields
    6. 7.5 Quantitative Chemical Analysis
    7. Key Terms
    8. Key Equations
    9. Summary
    10. Exercises
  9. 8 Gases
    1. Introduction
    2. 8.1 Gas Pressure
    3. 8.2 Relating Pressure, Volume, Amount, and Temperature: The Ideal Gas Law
    4. 8.3 Stoichiometry of Gaseous Substances, Mixtures, and Reactions
    5. 8.4 Effusion and Diffusion of Gases
    6. 8.5 The Kinetic-Molecular Theory
    7. 8.6 Non-Ideal Gas Behavior
    8. Key Terms
    9. Key Equations
    10. Summary
    11. Exercises
  10. 9 Thermochemistry
    1. Introduction
    2. 9.1 Energy Basics
    3. 9.2 Calorimetry
    4. 9.3 Enthalpy
    5. 9.4 Strengths of Ionic and Covalent Bonds
    6. Key Terms
    7. Key Equations
    8. Summary
    9. Exercises
  11. 10 Liquids and Solids
    1. Introduction
    2. 10.1 Intermolecular Forces
    3. 10.2 Properties of Liquids
    4. 10.3 Phase Transitions
    5. 10.4 Phase Diagrams
    6. 10.5 The Solid State of Matter
    7. 10.6 Lattice Structures in Crystalline Solids
    8. Key Terms
    9. Key Equations
    10. Summary
    11. Exercises
  12. 11 Solutions and Colloids
    1. Introduction
    2. 11.1 The Dissolution Process
    3. 11.2 Electrolytes
    4. 11.3 Solubility
    5. 11.4 Colligative Properties
    6. 11.5 Colloids
    7. Key Terms
    8. Key Equations
    9. Summary
    10. Exercises
  13. 12 Thermodynamics
    1. Introduction
    2. 12.1 Spontaneity
    3. 12.2 Entropy
    4. 12.3 The Second and Third Laws of Thermodynamics
    5. 12.4 Free Energy
    6. Key Terms
    7. Key Equations
    8. Summary
    9. Exercises
  14. 13 Fundamental Equilibrium Concepts
    1. Introduction
    2. 13.1 Chemical Equilibria
    3. 13.2 Equilibrium Constants
    4. 13.3 Shifting Equilibria: Le Châtelier’s Principle
    5. 13.4 Equilibrium Calculations
    6. Key Terms
    7. Key Equations
    8. Summary
    9. Exercises
  15. 14 Acid-Base Equilibria
    1. Introduction
    2. 14.1 Brønsted-Lowry Acids and Bases
    3. 14.2 pH and pOH
    4. 14.3 Relative Strengths of Acids and Bases
    5. 14.4 Hydrolysis of Salt Solutions
    6. 14.5 Polyprotic Acids
    7. 14.6 Buffers
    8. 14.7 Acid-Base Titrations
    9. Key Terms
    10. Key Equations
    11. Summary
    12. Exercises
  16. 15 Equilibria of Other Reaction Classes
    1. Introduction
    2. 15.1 Precipitation and Dissolution
    3. 15.2 Lewis Acids and Bases
    4. 15.3 Multiple Equilibria
    5. Key Terms
    6. Key Equations
    7. Summary
    8. Exercises
  17. 16 Electrochemistry
    1. Introduction
    2. 16.1 Balancing Oxidation-Reduction Reactions
    3. 16.2 Galvanic Cells
    4. 16.3 Standard Reduction Potentials
    5. 16.4 The Nernst Equation
    6. 16.5 Batteries and Fuel Cells
    7. 16.6 Corrosion
    8. 16.7 Electrolysis
    9. Key Terms
    10. Key Equations
    11. Summary
    12. Exercises
  18. 17 Kinetics
    1. Introduction
    2. 17.1 Chemical Reaction Rates
    3. 17.2 Factors Affecting Reaction Rates
    4. 17.3 Rate Laws
    5. 17.4 Integrated Rate Laws
    6. 17.5 Collision Theory
    7. 17.6 Reaction Mechanisms
    8. 17.7 Catalysis
    9. Key Terms
    10. Key Equations
    11. Summary
    12. Exercises
  19. 18 Representative Metals, Metalloids, and Nonmetals
    1. Introduction
    2. 18.1 Periodicity
    3. 18.2 Occurrence and Preparation of the Representative Metals
    4. 18.3 Structure and General Properties of the Metalloids
    5. 18.4 Structure and General Properties of the Nonmetals
    6. 18.5 Occurrence, Preparation, and Compounds of Hydrogen
    7. 18.6 Occurrence, Preparation, and Properties of Carbonates
    8. 18.7 Occurrence, Preparation, and Properties of Nitrogen
    9. 18.8 Occurrence, Preparation, and Properties of Phosphorus
    10. 18.9 Occurrence, Preparation, and Compounds of Oxygen
    11. 18.10 Occurrence, Preparation, and Properties of Sulfur
    12. 18.11 Occurrence, Preparation, and Properties of Halogens
    13. 18.12 Occurrence, Preparation, and Properties of the Noble Gases
    14. Key Terms
    15. Summary
    16. Exercises
  20. 19 Transition Metals and Coordination Chemistry
    1. Introduction
    2. 19.1 Occurrence, Preparation, and Properties of Transition Metals and Their Compounds
    3. 19.2 Coordination Chemistry of Transition Metals
    4. 19.3 Spectroscopic and Magnetic Properties of Coordination Compounds
    5. Key Terms
    6. Summary
    7. Exercises
  21. 20 Nuclear Chemistry
    1. Introduction
    2. 20.1 Nuclear Structure and Stability
    3. 20.2 Nuclear Equations
    4. 20.3 Radioactive Decay
    5. 20.4 Transmutation and Nuclear Energy
    6. 20.5 Uses of Radioisotopes
    7. 20.6 Biological Effects of Radiation
    8. Key Terms
    9. Key Equations
    10. Summary
    11. Exercises
  22. 21 Organic Chemistry
    1. Introduction
    2. 21.1 Hydrocarbons
    3. 21.2 Alcohols and Ethers
    4. 21.3 Aldehydes, Ketones, Carboxylic Acids, and Esters
    5. 21.4 Amines and Amides
    6. Key Terms
    7. Summary
    8. Exercises
  23. A | The Periodic Table
  24. B | Essential Mathematics
  25. C | Units and Conversion Factors
  26. D | Fundamental Physical Constants
  27. E | Water Properties
  28. F | Composition of Commercial Acids and Bases
  29. G | Standard Thermodynamic Properties for Selected Substances
  30. H | Ionization Constants of Weak Acids
  31. I | Ionization Constants of Weak Bases
  32. J | Solubility Products
  33. K | Formation Constants for Complex Ions
  34. L | Standard Electrode (Half-Cell) Potentials
  35. M | Half-Lives for Several Radioactive Isotopes
  36. Answer Key
    1. Chapter 1
    2. Chapter 2
    3. Chapter 3
    4. Chapter 4
    5. Chapter 5
    6. Chapter 6
    7. Chapter 7
    8. Chapter 8
    9. Chapter 9
    10. Chapter 10
    11. Chapter 11
    12. Chapter 12
    13. Chapter 13
    14. Chapter 14
    15. Chapter 15
    16. Chapter 16
    17. Chapter 17
    18. Chapter 18
    19. Chapter 19
    20. Chapter 20
    21. Chapter 21
  37. Index

16.1 Balancing Oxidation-Reduction Reactions

1.

If a 2.5 A current is run through a circuit for 35 minutes, how many coulombs of charge moved through the circuit?

2.

For the scenario in the previous question, how many electrons moved through the circuit?

3.

For each of the following balanced half-reactions, determine whether an oxidation or reduction is occurring.

(a) Fe3++3eFeFe3++3eFe

(b) CrCr3++3eCrCr3++3e

(c) MnO42−MnO4+eMnO42−MnO4+e

(d) Li++eLiLi++eLi

4.

For each of the following unbalanced half-reactions, determine whether an oxidation or reduction is occurring.

(a) ClCl2ClCl2

(b) Mn2+MnO2Mn2+MnO2

(c) H2H+H2H+

(d) NO3NONO3NO

5.

Given the following pairs of balanced half-reactions, determine the balanced reaction for each pair of half-reactions in an acidic solution.

(a) CaCa2++2e,CaCa2++2e, F2+2e2FF2+2e2F

(b) LiLi++e,LiLi++e, Cl2+2e2ClCl2+2e2Cl

(c) FeFe3++3e,FeFe3++3e, Br2+2e2BrBr2+2e2Br

(d) AgAg++e,AgAg++e, MnO4+4H++3eMnO2+2H2OMnO4+4H++3eMnO2+2H2O

6.

Balance the following in acidic solution:

(a) H2O2+Sn2+H2O+Sn4+H2O2+Sn2+H2O+Sn4+

(b) PbO2+HgHg22++Pb2+PbO2+HgHg22++Pb2+

(c) Al+Cr2O72−Al3++Cr3+Al+Cr2O72−Al3++Cr3+

7.

Identify the species that undergoes oxidation, the species that undergoes reduction, the oxidizing agent, and the reducing agent in each of the reactions of the previous problem.

8.

Balance the following in basic solution:

(a) SO32−(aq)+Cu(OH)2(s)SO42−(aq)+Cu(OH)(s)SO32−(aq)+Cu(OH)2(s)SO42−(aq)+Cu(OH)(s)

(b) O2(g)+Mn(OH)2(s)MnO2(s)O2(g)+Mn(OH)2(s)MnO2(s)

(c) NO3(aq)+H2(g)NO(g)NO3(aq)+H2(g)NO(g)

(d) Al(s)+CrO42−(aq)Al(OH)3(s)+Cr(OH)4(aq)Al(s)+CrO42−(aq)Al(OH)3(s)+Cr(OH)4(aq)

9.

Identify the species that was oxidized, the species that was reduced, the oxidizing agent, and the reducing agent in each of the reactions of the previous problem.

10.

Why is it not possible for hydroxide ion (OH) to appear in either of the half-reactions or the overall equation when balancing oxidation-reduction reactions in acidic solution?

11.

Why is it not possible for hydrogen ion (H+) to appear in either of the half-reactions or the overall equation when balancing oxidation-reduction reactions in basic solution?

12.

Why must the charge balance in oxidation-reduction reactions?

16.2 Galvanic Cells

13.

Write the following balanced reactions using cell notation. Use platinum as an inert electrode, if needed.

(a) Mg(s)+Ni2+(aq)Mg2+(aq)+Ni(s)Mg(s)+Ni2+(aq)Mg2+(aq)+Ni(s)

(b) 2Ag+(aq)+Cu(s)Cu2+(aq)+2Ag(s)2Ag+(aq)+Cu(s)Cu2+(aq)+2Ag(s)

(c) Mn(s)+Sn(NO3)2(aq)Mn(NO3)2(aq)+Au(s)Mn(s)+Sn(NO3)2(aq)Mn(NO3)2(aq)+Au(s)

(d) 3CuNO3(aq)+Au(NO3)3(aq)3Cu(NO3)2(aq)+Au(s)3CuNO3(aq)+Au(NO3)3(aq)3Cu(NO3)2(aq)+Au(s)

14.

Given the following cell notations, determine the species oxidized, species reduced, and the oxidizing agent and reducing agent, without writing the balanced reactions.

(a) Mg(s)Mg2+(aq)Cu2+(aq)Cu(s)Mg(s)Mg2+(aq)Cu2+(aq)Cu(s)

(b) Ni(s)Ni2+(aq)Ag+(aq)Ag(s)Ni(s)Ni2+(aq)Ag+(aq)Ag(s)

15.

For the cell notations in the previous problem, write the corresponding balanced reactions.

16.

Balance the following reactions and write the reactions using cell notation. Ignore any inert electrodes, as they are never part of the half-reactions.

(a) Al(s)+Zr4+(aq)Al3+(aq)+Zr(s)Al(s)+Zr4+(aq)Al3+(aq)+Zr(s)

(b) Ag+(aq)+NO(g)Ag(s)+NO3(aq)(acidic solution)Ag+(aq)+NO(g)Ag(s)+NO3(aq)(acidic solution)

(c) SiO32−(aq)+Mg(s)Si(s)+Mg(OH)2(s)(basic solution)SiO32−(aq)+Mg(s)Si(s)+Mg(OH)2(s)(basic solution)

(d) ClO3(aq)+MnO2(s)Cl(aq)+MnO4(aq)(basic solution)ClO3(aq)+MnO2(s)Cl(aq)+MnO4(aq)(basic solution)

17.

Identify the species oxidized, species reduced, and the oxidizing agent and reducing agent for all the reactions in the previous problem.

18.

From the information provided, use cell notation to describe the following systems:

(a) In one half-cell, a solution of Pt(NO3)2 forms Pt metal, while in the other half-cell, Cu metal goes into a Cu(NO3)2 solution with all solute concentrations 1 M.

(b) The cathode consists of a gold electrode in a 0.55 M Au(NO3)3 solution and the anode is a magnesium electrode in 0.75 M Mg(NO3)2 solution.

(c) One half-cell consists of a silver electrode in a 1 M AgNO3 solution, and in the other half-cell, a copper electrode in 1 M Cu(NO3)2 is oxidized.

19.

Why is a salt bridge necessary in galvanic cells like the one in Figure 16.4?

20.

An active (metal) electrode was found to gain mass as the oxidation-reduction reaction was allowed to proceed. Was the electrode part of the anode or cathode? Explain.

21.

An active (metal) electrode was found to lose mass as the oxidation-reduction reaction was allowed to proceed. Was the electrode part of the anode or cathode? Explain.

22.

The mass of three different metal electrodes, each from a different galvanic cell, were determined before and after the current generated by the oxidation-reduction reaction in each cell was allowed to flow for a few minutes. The first metal electrode, given the label A, was found to have increased in mass; the second metal electrode, given the label B, did not change in mass; and the third metal electrode, given the label C, was found to have lost mass. Make an educated guess as to which electrodes were active and which were inert electrodes, and which were anode(s) and which were the cathode(s).

16.3 Standard Reduction Potentials

23.

For each reaction listed, determine its standard cell potential at 25 °C and whether the reaction is spontaneous at standard conditions.

(a) Mg(s)+Ni2+(aq)Mg2+(aq)+Ni(s)Mg(s)+Ni2+(aq)Mg2+(aq)+Ni(s)

(b) 2Ag+(aq)+Cu(s)Cu2+(aq)+2Ag(s)2Ag+(aq)+Cu(s)Cu2+(aq)+2Ag(s)

(c) Mn(s)+Sn(NO3)2(aq)Mn(NO3)2(aq)+Sn(s)Mn(s)+Sn(NO3)2(aq)Mn(NO3)2(aq)+Sn(s)

(d) 3Fe(NO3)2(aq)+Au(NO3)3(aq)3Fe(NO3)3(aq)+Au(s)3Fe(NO3)2(aq)+Au(NO3)3(aq)3Fe(NO3)3(aq)+Au(s)

24.

For each reaction listed, determine its standard cell potential at 25 °C and whether the reaction is spontaneous at standard conditions.

(a) Mn(s)+Ni2+(aq)Mn2+(aq)+Ni(s)Mn(s)+Ni2+(aq)Mn2+(aq)+Ni(s)

(b) 3Cu2+(aq)+2Al(s)2Al3+(aq)+3Cu(s)3Cu2+(aq)+2Al(s)2Al3+(aq)+3Cu(s)

(c) Na(s)+LiNO3(aq)NaNO3(aq)+Li(s)Na(s)+LiNO3(aq)NaNO3(aq)+Li(s)

(d) Ca(NO3)2(aq)+Ba(s)Ba(NO3)2(aq)+Ca(s)Ca(NO3)2(aq)+Ba(s)Ba(NO3)2(aq)+Ca(s)

25.

Determine the overall reaction and its standard cell potential at 25 °C for this reaction. Is the reaction spontaneous at standard conditions?

Cu(s)Cu2+(aq)Au3+(aq)Au(s)Cu(s)Cu2+(aq)Au3+(aq)Au(s)

26.

Determine the overall reaction and its standard cell potential at 25 °C for the reaction involving the galvanic cell made from a half-cell consisting of a silver electrode in 1 M silver nitrate solution and a half-cell consisting of a zinc electrode in 1 M zinc nitrate. Is the reaction spontaneous at standard conditions?

27.

Determine the overall reaction and its standard cell potential at 25 °C for the reaction involving the galvanic cell in which cadmium metal is oxidized to 1 M cadmium(II) ion and a half-cell consisting of an aluminum electrode in 1 M aluminum nitrate solution. Is the reaction spontaneous at standard conditions?

28.

Determine the overall reaction and its standard cell potential at 25 °C for these reactions. Is the reaction spontaneous at standard conditions? Assume the standard reduction for Br2(l) is the same as for Br2(aq).
Pt(s)H2(g)H+(aq)Br2(aq),Br(aq)Pt(s)Pt(s)H2(g)H+(aq)Br2(aq),Br(aq)Pt(s)

16.4 The Nernst Equation

29.

For the standard cell potentials given here, determine the ΔG° for the cell in kJ.

(a) 0.000 V, n = 2

(b) +0.434 V, n = 2

(c) −2.439 V, n = 1

30.

For the ΔG° values given here, determine the standard cell potential for the cell.

(a) 12 kJ/mol, n = 3

(b) −45 kJ/mol, n = 1

31.

Determine the standard cell potential and the cell potential under the stated conditions for the electrochemical reactions described here. State whether each is spontaneous or nonspontaneous under each set of conditions at 298.15 K.

(a) Hg(l)+S2−(aq, 0.10M)+2Ag+(aq, 0.25M)2Ag(s)+HgS(s)Hg(l)+S2−(aq, 0.10M)+2Ag+(aq, 0.25M)2Ag(s)+HgS(s)

(b) The galvanic cell made from a half-cell consisting of an aluminum electrode in 0.015 M aluminum nitrate solution and a half-cell consisting of a nickel electrode in 0.25 M nickel(II) nitrate solution.

(c) The cell made of a half-cell in which 1.0 M aqueous bromide is oxidized to 0.11 M bromine ion and a half-cell in which aluminum ion at 0.023 M is reduced to aluminum metal. Assume the standard reduction potential for Br2(l) is the same as that of Br2(aq).

32.

Determine ΔG and ΔG° for each of the reactions in the previous problem.

33.

Use the data in Appendix L to determine the equilibrium constant for the following reactions. Assume 298.15 K if no temperature is given.

(a) AgCl(s)Ag+(aq)+Cl(aq)AgCl(s)Ag+(aq)+Cl(aq)

(b) CdS(s)Cd2+(aq)+S2−(aq)at 377 KCdS(s)Cd2+(aq)+S2−(aq)at 377 K

(c) Hg2+(aq)+4Br(aq)[HgBr4]2−(aq)Hg2+(aq)+4Br(aq)[HgBr4]2−(aq)

(d) H2O(l)H+(aq)+OH(aq)at 25°CH2O(l)H+(aq)+OH(aq)at 25°C

16.5 Batteries and Fuel Cells

34.

What are the desirable qualities of an electric battery?

35.

List some things that are typically considered when selecting a battery for a new application.

36.

Consider a battery made from one half-cell that consists of a copper electrode in 1 M CuSO4 solution and another half-cell that consists of a lead electrode in 1 M Pb(NO3)2 solution.

(a) What are the reactions at the anode, cathode, and the overall reaction?

(b) What is the standard cell potential for the battery?

(c) Most devices designed to use dry-cell batteries can operate between 1.0 and 1.5 V. Could this cell be used to make a battery that could replace a dry-cell battery? Why or why not.

(d) Suppose sulfuric acid is added to the half-cell with the lead electrode and some PbSO4(s) forms. Would the cell potential increase, decrease, or remain the same?

37.

Consider a battery with the overall reaction: Cu(s)+2Ag+(aq)2Ag(s)+Cu2+(aq).Cu(s)+2Ag+(aq)2Ag(s)+Cu2+(aq).

(a) What is the reaction at the anode and cathode?

(b) A battery is “dead” when it has no cell potential. What is the value of Q when this battery is dead?

(c) If a particular dead battery was found to have [Cu2+] = 0.11 M, what was the concentration of silver ion?

38.

An inventor proposes using a SHE (standard hydrogen electrode) in a new battery for smartphones that also removes toxic carbon monoxide from the air:
Anode: CO(g)+H2O(l)CO2(g)+2H+(aq)+2eEanode°=−0.53 VCathode:2H+(aq)+2eH2(g)Ecathode°=0 V¯Overall: CO(g)+H2O(l)CO2(g)+H2(g)Ecell°=+0.53 VAnode: CO(g)+H2O(l)CO2(g)+2H+(aq)+2eEanode°=−0.53 VCathode:2H+(aq)+2eH2(g)Ecathode°=0 V¯Overall: CO(g)+H2O(l)CO2(g)+H2(g)Ecell°=+0.53 V

Would this make a good battery for smartphones? Why or why not?

39.

Why do batteries go dead, but fuel cells do not?

40.

Explain what happens to battery voltage as a battery is used, in terms of the Nernst equation.

41.

Using the information thus far in this chapter, explain why battery-powered electronics perform poorly in low temperatures.

16.6 Corrosion

42.

Which member of each pair of metals is more likely to corrode (oxidize)?

(a) Mg or Ca

(b) Au or Hg

(c) Fe or Zn

(d) Ag or Pt

43.

Consider the following metals: Ag, Au, Mg, Ni, and Zn. Which of these metals could be used as a sacrificial anode in the cathodic protection of an underground steel storage tank? Steel is mostly iron, so use −0.447 V as the standard reduction potential for steel.

44.

Aluminum (EAl3+/Al°=−2.07 V)(EAl3+/Al°=−2.07 V) is more easily oxidized than iron (EFe3+/Fe°=−0.477 V),(EFe3+/Fe°=−0.477 V), and yet when both are exposed to the environment, untreated aluminum has very good corrosion resistance while the corrosion resistance of untreated iron is poor. Explain this observation.

45.

If a sample of iron and a sample of zinc come into contact, the zinc corrodes but the iron does not. If a sample of iron comes into contact with a sample of copper, the iron corrodes but the copper does not. Explain this phenomenon.

46.

Suppose you have three different metals, A, B, and C. When metals A and B come into contact, B corrodes and A does not corrode. When metals A and C come into contact, A corrodes and C does not corrode. Based on this information, which metal corrodes and which metal does not corrode when B and C come into contact?

47.

Why would a sacrificial anode made of lithium metal be a bad choice despite its ELi+/Li°=−3.04 V,ELi+/Li°=−3.04 V, which appears to be able to protect all the other metals listed in the standard reduction potential table?

16.7 Electrolysis

48.

Identify the reaction at the anode, reaction at the cathode, the overall reaction, and the approximate potential required for the electrolysis of the following molten salts. Assume standard states and that the standard reduction potentials in Appendix L are the same as those at each of the melting points. Assume the efficiency is 100%.

(a) CaCl2

(b) LiH

(c) AlCl3

(d) CrBr3

49.

What mass of each product is produced in each of the electrolytic cells of the previous problem if a total charge of 3.33 ×× 105 C passes through each cell? Assume the voltage is sufficient to perform the reduction.

50.

How long would it take to reduce 1 mole of each of the following ions using the current indicated? Assume the voltage is sufficient to perform the reduction.

(a) Al3+, 1.234 A

(b) Ca2+, 22.2 A

(c) Cr5+, 37.45 A

(d) Au3+, 3.57 A

51.

A current of 2.345 A passes through the cell shown in Figure 16.20 for 45 minutes. What is the volume of the hydrogen collected at room temperature if the pressure is exactly 1 atm? Assume the voltage is sufficient to perform the reduction. (Hint: Is hydrogen the only gas present above the water?)

52.

An irregularly shaped metal part made from a particular alloy was galvanized with zinc using a Zn(NO3)2 solution. When a current of 2.599 A was used, it took exactly 1 hour to deposit a 0.01123-mm layer of zinc on the part. What was the total surface area of the part? The density of zinc is 7.140 g/cm3. Assume the efficiency is 100%.

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