AP Net Ionic Equations

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AP Net Ionic Equations
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• AP equations are found in the free response
  section of the AP test. You will have 3
  equations following by a question about the
  reaction. The equations are of mixed types.

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• The sections is worth 15 points and is 10 of the
  free response grade. Free response is 50 of the
  total AP test grade.

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• All AP equations work. In each case, a
  reaction will occur. These equations need to be
  written in net ionic form. All spectator ions
  must be left out and all ions must be written in
  ionic form.

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• Answer 3 equations that must be balanced.
• Each equation is followed by a question.
• 1 pt for reactants, 2 points for products, and 1
  pt for each question.

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• Strong Acids are
• Exception concentrated sulfuric acid-keep
  together because it really is 97 H2SO4 and 3
  water in the jug.
• Strong Bases are

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• Weak acids and bases keep together

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• All molecular substances and nonsoluble compounds
  must be written together (not ionized!).

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Know your solubility rules!!!

• Ca(OH)2 and Sr(OH) 2 are moderately soluble and
  can be written together or as ions.
• Ba(OH)2 is soluble and Mg(OH)2 is insoluble.
• CaSO4 and SrSO4 are moderately soluble and can be
  written together or as ions.
• Weak electrolytes, such as acetic acid, are not
  ionized.
• Solids and pure liquids are written together,
  also.
• A saturated solution is written in ionic form
  while a suspension is written together.

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Double Replacement

• Two compounds react to form two new compounds.
  No changes in oxidation numbers occur. All
  double replacement reactions must have a driving
  force that removes a pair of ions from solution.

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• Manganese(II) nitrate solution is mixed with a
  sodium hydroxide solution

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• Excess hydrochloric acid is added to an aqueous
  solution of potassium sulfite

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• Hydrogen sulfide gas is bubbled through a
  solution of lead(II) nitrate

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• A solution of ammonium sulfate is added to a
  potassium hydroxide solution

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• Solutions of tripotassium phosphate and zinc
  nitrate are mixed

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• Gaseous hydrofluoric acid reacts with solid
  silicon dioxide.

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Single Replacement Rxns

• Treat like redox reactions.
• Reaction where one element displaces another in a
  compound. One element is oxidized and another is
  reduced.
• A BC ? B AC
• charges replace and
• charges replace -

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• Active metals replace less active metals or
  hydrogen from their compounds in aqueous
  solution.

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• Active nonmetals replace less active nonmetals
  from their compounds in aqueous solution. Each
  halogen will displace less electronegative
  (heavier) halogens from their binary salts.

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Examples

• A piece of aluminum metal is added to a solution
  of silver nitrate

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• Small chunks of solid sodium are added to water

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• Chlorine gas is bubbled into a solution of sodium
  bromide

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• Magnesium turnings are added to a solution of
  iron(III) chloride

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Anhydrides

• Anhydride means without water.
• Water is a reactant in each of these equations.

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Memorize the Rules

• Look for
• 1. Oxides H2O
• a. metallic oxide H2O ? base
• b. nonmetallic oxide H2O ? acid

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• 2. Metal hydride H2O? metal hydroxide H2

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• 3. Group 1 and 2 nitride H2O?
• metal hydroxide NH3

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• 4. Phosphorus halide H2O ?
• H3PO4 or H3PO3 H(halide) acid

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Examples

• Excess water is added to solid calcium hydride

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• Solid lithium hydride is added to water

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• Solid dinitrogen pentoxide is added to water

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• Solid potassium oxide is added to water

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• Phosphorus pentachloride solid is added to water

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• Methylamine gas is bubbled into distilled water

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Oxidation-Reduction Reactions

• Redox reactions involve the transfer of
  electrons. The oxidation numbers of at least two
  elements must change.
• Single replacement, some combination and some
  decomposition reactions are redox reactions.

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• To predict the products of a redox reaction, look
  at the reagents given to see if there is both an
  oxidizing agent and a reducing agent.
• When a problem mentions an acidic or basic
  solution, it is probably redox.

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Common oxidizing agent Product formed

MnO4- in acidic solution Mn2
MnO2 in acidic solution Mn2
MnO4- in neutral or basic solution MnO2 (s)
Cr2O72- in acidic solution Cr3
HNO3, concentrated NO2
HNO3, dilute NO
H2SO4, hot, concentrated SO2
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Common oxidizing agent Product formed

Metal-ic ions Metal-ous ions
Free halogens Halide ions
Na2O2 NaOH
HClO4 Cl-
H2O2 H2O
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Common reducing agent Product formed

Halide ions Free halogen
Free metals Metal ions
Sulfite ions or SO2 Sulfate ions
Nitrite ions Nitrate ions
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Common reducing agent Product formed

Free halogens, dilute basic solution Hypohalite ions
Free halogens, conc. basic solution Halate ions
Metal-ous ions Metal-ic ions
H2O2 O2
C2O42- CO2
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Examples

• A solution of tin(II) chloride is added to an
  acidified solution of potassium permanganate.

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• Hydrogen peroxide solution is added to a solution
  of iron(II) sulfate

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• Potassium permanganate solution is added to a
  solution of oxalic acid acidified with a few
  drops of sulfuric acid.

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• A piece of iron is added to a solution of
  iron(III) sulfate.

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• Solid sodium dichromate is added to an acidified
  solution of sodium iodide

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• Potassium permanganate is mixed with an alkaline
  solution of sodium sulfite

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• Copper (II) sulfide is oxidized by dilute nitric
  acid.

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• A solution of potassium iodide is added to an
  acidified solution of potassium dichromate.

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Acid-Base Neutralization Rxns

• Acids react with bases to produce water and
  salts.

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Examples

• Hydrogen sulfide gas is bubbled through a
  solution of potassium hydroxide

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• A solution of sodium hydroxide is added to a
  solution of sodium dihydrogen phosphate until the
  same number of moles of each compound has been
  added

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• Nitric acid is added to crystals of pure calcium
  oxide

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• Carbon dioxide is bubbled through a solution of
  sodium hydroxide

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Decomposition Reactions

• Reaction where a compound breaks down into two or
  more elements or compounds. Heat, electrolysis,
  or a catalyst is usually necessary.

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• Memorize the rules!
• 1. Metal Carbonate ? Metal oxide CO2
• 2. Metal Chlorate ? Metal chloride O2

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• 3. Hydrogen peroxide? water oxygen
• 4. Ammonium carbonate? ammonia water
  carbon dioxide
• 5. Sulfurous acid ? Sulfur dioxide water
• 6. Carbonic acid ? carbon dioxide water

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Examples

• A solution of hydrogen peroxide is heated

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• Magnesium carbonate is heated

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• Potassium chlorate is heated in the presence of
  manganese dioxide

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• Solid ammonium carbonate is heated

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Addition Reactions

• Two or more elements or compounds combine to form
  a single product.

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Memorize the rules! Most of these should already
look familiar.

• 1. 2 cmpds ? form one compound
• 2. If excess use the higher oxidation number
• If limited use the lower oxidation number

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• 3. Nonmetal oxide water ? acid
• 4. Metal oxide water ? base
• 5. Metal oxide sulfur dioxide ?Metal sulfite
• 6. Metal oxide carbon dioxide ? metal
  carbonate

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Examples

• Magnesium oxide is added to a container of carbon
  dioxide gas

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• Solid calcium oxide is heated in the presence of
  sulfur trioxide gas

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• Calcium metal is heated strongly in nitrogen gas

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• The gases boron trifluoride and ammonia are mixed

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Combustion Reactions

• -Elements or compounds combine with oxygen.

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Memorize these rules.

• Hydrocarbon oxygen ? carbon dioxide
  water
• 2. ammonia oxygen ? NO H2O
• if excess O2 ? NO2 H2O

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• 3. Nonmetal hydride oxygen ? nonmetal
  oxide water
• 4. Nonmetal sulfideoxygen ? nonmetal
  oxide sulfur dioxide

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• Methane is burned in the presence of oxygen

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• Lithium metal is burned in air

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• Solid zinc sulfide is heated in an excess of
  oxygen

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• A piece of solid bismuth is heated strongly in
  oxygen

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Complex Ion Reactions

• Complex ions are made up of a ____________ and a
  _____________.
• Co(NH3)63 is the complex ion
• NH3 is the ligand, Co is the metal

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• Possible metals Cu/Zn/Ag/Cd/Fe/Al
• Possible ligands NH3, OH-1, SCN-1
• Magic number? Double charge to get magic number
• Exceptions to the trick
• Al(OH)4- Fe(SCN)2

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• Example
• Co(NH3)6 Cl3
• NH3 is the ligand, Co(NH3)63 is the complex ion

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Common complex ions on AP equations

• Al(OH)4- tetrahydroxoaluminate ion
• formed from (Al or Al(OH)3 or Al3 OH-)
• Ag(NH3)2 diamminesilver(I) ion
• formed from (Ag NH3)

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• Zn(OH)42- tetrahydroxyzincate ion
• formed from (Zn(OH)2 OH-)
• Zn(NH3)42 tetramminezinc ion
• formed from (Zn2 NH3)
• Cu(NH3)42 tetraminecopper(II) ion
• formed from (Cu2 NH3)

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• Cd(NH3)42 tetraminecadmium(II) ion
• formed from (Cd2 NH3)
• Fe(SCN)2 thiocyanairon(III) ion
• formed from (Fe3 SCN-)
• Ag(CN)2- dicyanoargentate(I) ion
• formed from (Ag and CN-)

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• Remember the following when writing complex ion
  reactions
• Acid to complex ion ? break it up
• 2. Acid to NH3 complex ? NH4 breakup
  complex ion
• 3. HCl Ag complex ? AgCl Breakup
  complex ion

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Examples

• Concentrated (15M) ammonia is added in excess to
  a solution of copper (II) nitrate

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• Dilute hydrochloric acid is added to a solution
  of tetraminecopper (II) sulfate

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• A suspension of zinc hydroxide is treated with
  concentrated sodium hydroxide solution

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• Solid silver chloride is added to a concentrated
  solution of ammonia

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• Hydrochloric acid is added to a solution of
  dihydroxysilver bromide