AP Net Ionic Equations

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.

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

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.

• 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.

• Strong Acids are:

Exception: concentrated sulfuric acid-keep together because it really is 97% H2SO4 and 3% water in the jug.

• Strong Bases are:

Weak acids and bases keep together

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

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.

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.

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

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

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

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

• Solutions of tripotassium phosphate and zinc nitrate are mixed

• Gaseous hydrofluoric acid reacts with solid silicon dioxide.

Single Replacement RxnsTreat 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 -

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

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

Examples

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

• Small chunks of solid sodium are added to water

• Chlorine gas is bubbled into a solution of sodium bromide

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

Anhydrides

Anhydride means “without water.”

Water is a reactant in each of these equations.

Memorize the Rules

Look for:

1. Oxides + H2O

a. metallic oxide + H2O base

b. nonmetallic oxide + H2O acid

2. Metal hydride + H2O metal hydroxide + H2

3. Group 1 and 2 nitride + H2O

metal hydroxide + NH3

4. Phosphorus halide + H2O

H3PO4 or H3PO3 + H(halide) acid

Examples

• Excess water is added to solid calcium hydride

• Solid lithium hydride is added to water

• Solid dinitrogen pentoxide is added to water

• Solid potassium oxide is added to water

• Phosphorus pentachloride solid is added to water

• Methylamine gas is bubbled into distilled water

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.

• 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.

Common oxidizing agent Product formed

MnO4- in acidic solution Mn2+

MnO2 in acidic solution Mn2+

MnO4- in neutral or basic

solutionMnO2 (s)

Cr2O72- in acidic solution Cr3+

HNO3, concentrated NO2

HNO3, dilute NO

H2SO4, hot, concentrated SO2

Common oxidizing agent Product formed

Metal-ic ions Metal-ous ions

Free halogens Halide ions

Na2O2 NaOH

HClO4 Cl-

H2O2 H2O

Common reducing agent Product formed

Halide ions Free halogen

Free metals Metal ions

Sulfite ions or SO2 Sulfate ions

Nitrite ions Nitrate ions

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

Examples

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

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

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

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

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

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

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

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

Acid-Base Neutralization Rxns

Acids react with bases to produce water and salts.

Hydrogen sulfide gas is bubbled through a solution of potassium hydroxide

Examples

• 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

• Nitric acid is added to crystals of pure calcium oxide

• Carbon dioxide is bubbled through a solution of sodium hydroxide

Decomposition Reactions

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

Memorize the rules!

1. Metal Carbonate Metal oxide + CO2

2. Metal Chlorate Metal chloride + O2

3. Hydrogen peroxide water + oxygen

4. Ammonium carbonate ammonia + water + carbon

dioxide

5. Sulfurous acid Sulfur dioxide + water

6. Carbonic acid carbon dioxide + water

• A solution of hydrogen peroxide is heated

Examples

• Magnesium carbonate is heated

• Potassium chlorate is heated in the presence of manganese dioxide

• Solid ammonium carbonate is heated

Addition Reactions

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

1. 2 cmpds form one compound

2. If excess use the higher oxidation number

If limited use the lower oxidation number

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

3. Nonmetal oxide + water acid

4. Metal oxide + water base

5. Metal oxide + sulfur dioxide Metal sulfite

6. Metal oxide + carbon dioxide metal carbonate

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

Examples

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

• Calcium metal is heated strongly in nitrogen gas

• The gases boron trifluoride and ammonia are mixed

Combustion Reactions

-Elements or compounds combine with oxygen.

Memorize these rules.

1. Hydrocarbon + oxygen carbon dioxide

+ water

2. ammonia + oxygen NO + H2O

if excess O2 NO2 + H2O

3. Nonmetal hydride + oxygen nonmetal oxide+ water

4. Nonmetal sulfide+oxygen nonmetal oxide + sulfur

dioxide

• Methane is burned in the presence of oxygen

• Lithium metal is burned in air

• Solid zinc sulfide is heated in an excess of oxygen

• A piece of solid bismuth is heated strongly in oxygen

Complex Ion Reactions

• Complex ions are made up of a ____________ and a _____________.

[Co(NH3)6]+3 is the complex ion

NH3 is the ligand, Co is the metal

• 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+

Example:

[Co(NH3)6] Cl3

NH3 is the ligand, [Co(NH3)6]+3 is the complex ion

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)

[Zn(OH)4]2- tetrahydroxyzincate ion

formed from (Zn(OH)2 + OH-)

[Zn(NH3)4]2+ tetramminezinc ion

formed from (Zn2+ + NH3)

[Cu(NH3)4]2+ tetraminecopper(II) ion

formed from (Cu2+ + NH3)

[Cd(NH3)4]2+ 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-)

Remember the following when writing complex ion reactions:

1. Acid to complex ion break it up

2. Acid to NH3 complex NH4+ + breakup

complex ion

3. HCl + Ag complex AgCl + Breakup complex ion

Examples

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

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

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

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

• Hydrochloric acid is added to a solution of dihydroxysilver bromide