Reactions and Periodicity: Review Questions for AP Chemistry (page 2)

By — McGraw-Hill Professional
Updated on Feb 1, 2011

Answers and Explanations

  1. D—The balanced equation is:
  2. 3Fe(OH)2(s) + 2H3PO4(aq) → Fe3(PO4)2(s) + 6H2O(l)

  3. B—Carbonates produce carbon dioxide gas in the presence of an acid.
  4. D—Aluminum hydroxide, Al(OH)3, forms initially but then dissolves to form the Al(OH)4 ion.
  5. A—Aqueous solutions of Cu2+ are normally blue. Iron ions give a variety of colors, but are normally colorless, or nearly so, in the absence of complexing agents. All the others are colorless.
  6. B—Lead(II) carbonate is insoluble, so its formula should be left as PbCO3. Hydrochloric acid is a strong acid so it should be written as separate H+ and Cl ions. Lead(II) chloride, PbCl2, is insoluble, and carbonic acid, H2CO3, quickly decomposes to CO2 and H2O.
  7. C—The balanced chemical equation is:
  8. 3Cu + 8HNO3 → 3Cu(No3)2 + 2NO + 4H2O

    The copper is below hydrogen on the activity series, so H2 cannot be formed by this acid–metal reaction. Nitric acid is an oxidizing agent, which will oxidize copper to Cu2+ giving Cu(NO3)2.

  9. A—Acetic acid is a weak acid; as such it should appear as HC2H3O2. Potassium hydroxide is a strong base so it will separate into K+ and OH ions. The potassium ion is a spectator ion, and is left out of the net ionic equation.
  10. E—Aqueous ammonia contains NH3. The reaction produces the silver–ammonia complex, [Ag(NH3)2]+.
  11. A—The reaction is:
  12. 2K + 2H2O → 2KOH + H2

    KOH is a water-soluble strong base, not an acid. As a strong base it will react with an acid. Iron(II) hydroxide, Fe(OH)2, is insoluble and will precipitate.

  13. E—Aqueous ammonia contains NH3. The charges on each side of the reaction arrow must be equal.
  14. B—Neither B nor C is soluble in water. Only B will react will nitric acid, and will dissolve.
  15. D—The magnesium chloride gives 0.20 moles of chloride ion, and the potassium chloride gives 0.10 moles of chloride ion. A total of 0.30 moles of chloride will react with 0.15 moles of lead, because two Cl require one Pb2+.
  16. D—The HCl will react with one-half the silver to halve the concentration. The doubling of the volume halves the concentration a second time.
  17. B—All the potassium and nitrate ions remain in solution. However, two nitrate ions are produced per solute formula as opposed to only one potassium ion. The lead and potassium would be equal, but some of the lead is precipitated as PbCl2.
  18. C—Ammonia, as a base, will precipitate the metal hydroxides. Chromate, sulfide, and chloride ions will precipitate one or more of the ions.
  19. E—Chlorine is an oxidizing agent. It is capable of oxidizing both B and E. Answer B gives I2, which is brownish in water and purplish in methylene chloride. Answer E gives reddish Br2.
  20. D—The following reaction occurs: NH4 +(aq) + OH-(aq) → NH3(g) + H2O(l)
  21. B—The precipitate is PbCrO4.
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