Chapter 4. Chemical Reactions and Equations

21 End-of-Chapter Material

Additional Exercises

  1. Chemical equations can also be used to represent physical processes. Write a chemical reaction for the boiling of water, including the proper phase labels.
  2. Chemical equations can also be used to represent physical processes. Write a chemical reaction for the freezing of water, including the proper phase labels.
  3. Explain why 4Na(s) + 2Cl2(g) → 4NaCl(s) should not be considered a proper chemical equation.
  4. Explain why H2(g) + ½O2(g) → H2O(ℓ) should not be considered a proper chemical equation.
  5. Does the chemical reaction represented by 3Zn(s) + 2Al(NO3)3(aq) → 3Zn(NO3)2(aq) + 2Al(s) proceed as written? Why or why not?
  6. Does the chemical reaction represented by 2Au(s) + 2HNO3(aq) → 2AuNO3(aq) + H2(g) proceed as written? Gold is a relatively useful metal for certain applications, such as jewellry and electronics. Does your answer suggest why this is so?
  7. Explain what is wrong with the double-replacement reaction
    NaCl(aq) + KBr(aq) → NaK(aq) + ClBr(aq).
  8. Predict the products of and balance the double-replacement reaction Ag2SO4(aq) + SrCl2(aq) → ?
  9. Write the complete and net ionic equations for the double-replacement reaction
    BaCl2(aq) + Ag2SO4(aq) → ?
  10. Write the complete and net ionic equations for the double-replacement reaction
    Ag2SO4(aq) + SrCl2(aq) → ?
  11. Identify the spectator ions in the reaction NaCl(aq) + KBr(aq) → NaBr(aq) + KCl(aq). What is the net ionic equation?
  12. Complete the reaction 3H2SO4(aq) + 2Al(OH)3(s) → ? and identify the spectator ions. What is the net ionic equation?
  13. Can a reaction be a composition reaction and a redox reaction at the same time? Give an example to support your answer.
  14. Can a reaction be a combustion reaction and a redox reaction at the same time? Give an example to support your answer.
  15. Can a reaction be a decomposition reaction and a redox reaction at the same time? Give an example to support your answer.
  16. Can a reaction be a combustion reaction and a double-replacement reaction at the same time? Give an example to support your answer.
  17. Why is CH4 not normally considered an acid?
  18. Methyl alcohol has the formula CH3OH. Why would methyl alcohol not normally be considered a base?
  19. What are the oxidation numbers of the nitrogen atoms in these substances?
    1. N2
    2. NH3
    3. NO
    4. N2O
    5. NO2
    6. N2O4
    7. N2O5
    8. NaNO3
  20. What are the oxidation numbers of the sulfur atoms in these substances?
    1. SF6
    2. Na2SO4
    3. K2SO3
    4. SO3
    5. SO2
    6. S8
    7. Na2S
  21. Disproportion is a type of redox reaction in which the same substance is both oxidized and reduced. Identify the element that is disproportionating in 2CuCl(aq) → CuCl2(aq) + Cu(s) and indicate the initial and final oxidation numbers of that element.
  22. Disproportion is a type of redox reaction in which the same substance is both oxidized and reduced. Identify the element that is disproportionating in
    3Cl2(g) + 6OH(aq) → 5Cl(aq) + ClO3(aq) + 3H2O(ℓ) and indicate the initial and final oxidation numbers of that element.

Answers

  1. H2O(ℓ) → H2O(g)
  1. The coefficients are not in their lowest whole-number ratio.
  1. No; zinc is lower in the activity series than aluminum.
  1. In the products, the cation is pairing with the cation, and the anion is pairing with the anion.
  1. Complete ionic equation: Ba2+(aq) + 2Cl(aq) + 2Ag+(aq) + SO42−(aq) → BaSO4(s) + 2AgCl(s)

    Net ionic equation: The net ionic equation is the same as the complete ionic equation.

  1. Each ion is a spectator ion; there is no overall net ionic equation.
  1. Yes; H2 + Cl2 → 2HCl (answers will vary)
  1. Yes; 2HCl → H2 + Cl2 (answers will vary)
  1. It does not increase the H+ ion concentration; it is not a compound of H+.
    1. 0
    2. −3
    3. +2
    4. +1
    5. +4
    6. +4
    7. +5
    8. +5
  1. Copper is disproportionating. Initially, its oxidation number is +1; in the products, its oxidation numbers are +2 and 0, respectively.