Writing AP Equations

Warm Up – try these!

Write the net ionic eqn and answer the question:

1. dilute sulfuric acid is added to a solution of barium acetate

1. identify the spectator ions in this reaction; explain.

2. solutions of zinc sulfate and sodium phosphate are mixed

1. if a wire loop is dipped into the final reaction mixture and placed in a flame, what color will the flame turn?

Today’s Agenda• QOTD: How to write a net ionic equation for

metathesis and displacement reactions?

• (answer gases question…)

• AP equation section.

• Writing a net ionic

• Metathesis

• Simple redox (single replacement)

• Homework: Equation Set 1

Writing AP Equations

AP equation sets are found in the free-response section of the AP test. You are given 3

equations. The equations are of mixed types. The section is worth 15 points and is 15 % of the free response grade. Free response is 55% of the

total AP test grade.

First classify the type of reaction.

Practice these!!! Speed and accuracy!

Types of Reactions• 1. Metathesis (double replacement) • 2. Single replacement • 3. Combustion • 4. Acid/base neutralization • 5. Combination • 6. Decomposition • 7. Reactions of anhydrides • 8. Organic • 9. Non-trivial redox• 10. Complex ion formation or decomposition • 11. Lewis acid/base (adduct formation)

Categories of Chemical Compounds

• Acids - 7 Strong acids: HCl, HBr, HI, HNO3, H2SO4, HClO3, HClO4 to KNOW…all others dissolve but only partially dissociate!!

• Bases – Strong bases: Group I and II hydroxides. • Metal oxides -binary compounds of a metal and

oxygen (MgO, K2O)• Non-metal oxides - binary compounds of a non-

metal and oxygen (NO, CO2) • Salts (compounds of metals that are NEITHER

bases NOR oxides: see solubility rules!) • Other (most compounds belong here!!!!!)

Soluble Salts (with exceptions)

NH4+

NitrateAcetate

S2-

Water

• Consider water as HOH (H+, OH-)

• Water is a good solvent because the molecules are polar.

• The oxygen atoms have a partial negative charge.

• The hydrogen atoms have a partial positive charge.

• The angle is 105°

How Ionic solids dissolve

HH

H

HH

Click here for Animation

Writing Net Ionic Equations

• All reactions will work, they never give you a reactions that doesn’t proceed to products.

• Break up any IONIC compounds (salts, strong acids, strong bases…)

• Covalent compounds, weak electrolytes, weak acids and bases, solids, pure liquids, and gases are NOT broken into ions!

• Suspensions are NOT broken into ions.

Metathesis (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.

HCl + NaOH → NaCl + HOH

AgNO3 + NaCl → AgCl + NaNO3

Warm Up from HW

• 1. A solution of copper(II) sulfate is added to a solution of barium hydroxide.

• 2. Equal volumes of dilute equimolar solutions of sodium carbonate and hydrochloric acid are mixed.

• 3. Solid barium peroxide is added to cold dilute sulfuric acid.

Today’s Agenda• Question for today: What is a redox?

• Finish metathesis

• Displacement reactions

• Combustion reactions

• Combination/Decomposition

• Lab and test corrections due tomorrow. Leave notebooks in bin!

Metathesis Products• Precipitate : insoluble substance formed by the

reaction of two aqueous substances. Two ions bond together so strongly that water can not pull them apart.

i.e. Solutions of silver nitrate and lithium bromide are mixed

• Gas : Gases may form directly in a double replacement reaction or can form from the decomposition of a product such as H2CO3 or H2SO3.

i.e. Excess hydrochloric acid solution is added to a solution of potassium sulfite

• Molecular substance: When a molecular substance such as water or acetic acid is formed, ions are removed from solution and the reaction "works".

i.e. Dilute solutions of lithium hydroxide and hydrobromicacid are mixed

Practice Problems

Sodium hydroxide is mixed with phosphoric acid.

Hydrogen sulfide is bubbled through a solution of silver nitrate.

Single Replacement (displacement)

Reaction where one element displaces another in a compound (Trivial redox).

A + BC B + ACThe more easily oxidized metal replaces the less easily oxidized metal. The metal with the most negative reduction potential will be the most active. Each halogen will displace less electronegative (heavier) halogens from their binary salts (F replaces Cl).

Remember there are no “no reactions”!!!

Most Active Metals on Top!

Reaction of Na+ and K+ with water…

Redox Review (or quick intro)

• In a redox reaction 1 substance is oxidized and the other is reduced.

• Oxidation – The substance that loses electrons– Charge becomes MORE positive!

• Reduction – The substance that gains electrons– Charge becomes LESS positive, (+ # decreases)

L.E.O. the lion says G.E.R.

Redox Practice

• Magnesium metal is added to a solution of iron (III) chloride.

• 3 Mg0 + 2 FeCl3 2 Fe0 + 3 MgCl2– 3 Mg0 + 2 Fe3+ + 6Cl- 2 Fe0 + 3 Mg2+ + 6Cl-

• Which is oxidized and which is reduced?

Try these

• Aluminum metal is added to a solution of copper (II) nitrate.

– Which is oxidized and which is reduced?

• Fluorine gas is bubbled through a solution of potassium chloride.

– Which is oxidized and which is reduced?

Special Cases• Non-aqueous: gas over hot metal oxides – no net ionics

• Weak acid/bases replaced by stronger acids/bases. What indicates completion?– NH4Cl + NaOH → NH3 + NaCl + H2O [molecular]

• Polyprotic acids i.e. H3PO4

– weak polyprotic acids will only reform step-by-step. The extent to which the acid reforms depends on the amount of stronger acid added.

• Equal volumes of equimolar solutions of sodium hydrogen phosphate and hydrochloric acid are mixed : HPO4

2- + H+ → H2PO4-

• Equal volumes of 0.10 M sodium hydrogen phosphate and 0.20 M hydrochloric acid are mixed : HPO4

2- + 2 H+ → H3PO4

– Notice that in the second case there is twice as much H+ available so the reaction goes an additional step.

Single and Double Displacement Practice

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

– identify the spectator ions in this reaction; explain

• Solutions of zinc sulfate and sodium phosphate are mixed

– if a wire loop is dipped into the final reaction mixture and placed in a flame, what color will the flame turn?

• Sulfur trioxide gas is bubbled into a solution of sodium hydroxide

– is the temperature of the mixture likely to increase or decrease?

Combustion

• Reactions where elements or compounds combine with O2

• Hydrocarbons or alcohols combine with O2 to form CO2 and H2O.

• Ammonia (NH3) combines with limited O2 to produce NO and water OR excess O2 to produce NO2 and H2O.

• Nonmetallic sulfides combine with oxygen to form oxides and SO2.

If you add EXCESS oxygen, you make XO2 gases!

Combustion Practice

Carbon disulfide vapor is burned in excess O2.

Ethanol is burned completely in air.

Solid copper(II) sulfide is heated strongly in O2.

The hydrocarbon hexane (C6H14) is burned in excess O2

Warm Up

• Aluminum metal is added to a solution of copper (II) nitrate.

– Which is oxidized and which is reduced?

• Fluorine gas is bubbled through a solution of potassium chloride.

– Which is oxidized and which is reduced?

Today’s Agenda• Question: Can elements just combine, and is it

the same but opposite as if compounds just decompose?

• Addition/Decomposition• Anhydrides• Complex Ion

• Homework Set 2. Problem Set 2 – Gases due Friday for quiz grade.

Addition/Combination Reactions

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

• Group IA or IIA metal may combine with a nonmetal to make a salt.

– A higher oxidation state of one nonmetal is obtained when reacting with an excess of the other nonmetal.

• Two nonmetals may combine to form a molecular compound.

Addition Reactions

• A metallic oxide plus carbon dioxide yields a metallic carbonate. (Carbon keeps the same oxidation state)

• A metallic oxide plus sulfur dioxide yields a metallic sulfite. (Sulfur keeps the same oxidation state)

• A metallic oxide plus water yields a metallic hydroxide.

• A nonmetallic oxide plus water yields an acid.

Addition Reaction Practice

• Solid calcium oxide is exposed to a stream of carbon dioxide gas.

• Calcium metal is heated strongly in nitrogen gas.

• A piece of lithium metal is dropped into a container of nitrogen gas

• Sulfur dioxide gas is passed over solid calcium oxide

Decomposition ReactionsBasically, the opposite of a combination rxn.

• Common decomp’s that you’ll see:

metal carbonates → carbon dioxide + metal oxide

CaCO3 → CO2 + CaO

metal hydrogen carbonates → CO2 + metal carbonate + H2O

2 NaHCO3 → CO2 + Na2CO3 + H2O

metal halates → oxygen + metal halide

2 KClO3→ 3 O2 + 2 KCl

metal sulfites → sulfur dioxide + metal oxide

CaSO3→ SO2 + CaO

hydrogen peroxide → oxygen + water

2 H2O2 → O2 + 2 H2O

Decomposition Practice

solid potassium chlorate is heated in the presence of a manganese(IV) oxide catalyst, resulting in a change in the oxidation states of both the chlorine and the oxygen

- what is the oxidation number of chlorine before and after the reaction?

a solution of hydrogen peroxide is heated – which element changes in oxidation state? How can

there be only one?

Anhydride Reactions

• Anhydride – without water. Water is a reactant in these equations.

• Nonmetallic oxides (fake acid) plus water yield acids

i.e. Carbon dioxide is bubbled into water

• Metallic oxides (fake base) plus water yield bases

i.e. Solid sodium oxide is added to water

Anhydride Reactions

• Metal hydride + H2O metal hydroxide + H2

• Phosphorous halides + H2O hydrohalic acid + phosphorous containing acid.

• RNH3 – amine, organic base

CH3NH3 + H2O OH- + RNH4+

Anhydride Practice

• Excess water is added to solid calcium hydride

• Solid lithium hydride is added to water

• Solid dinitrogen pentoxide is added to water

• Phosphorus pentachloride solid is added to water

• Solid potassium oxide is added to water

• Methylamine gas is bubbled into distilled water

Acid/Base Neutralizations

•Acids react with bases to produce salts and water.

One mole of hydrogen ions react with one mole of hydroxide ions to produce one mole of water.

Watch out for information about quantities of each reactant! Remember which acids are strong (ionize completely) and which are weak (write as molecule).

Complex Ion Reactions

• Complex ion- the combination of a central metal ion and its ligands

• Ligand- group bonded to a metal ion

• Coordination compound- a neutral compound containing complex ions

[Co(NH3)6]Cl3 (NH3 is the ligand, [Co(NH3)6]3+is the complex ion)

Complex ion Name Formed from:

• [Al(OH)4]- tetrahydroxoaluminate ion (Al or Al(OH)3 or Al3++ OH-)

• [Ag(NH3)2]+ diamminesilver(I) ion (Ag+ + NH3)

• [Zn(OH)4] 2- tetrahydroxozincate ion (Zn(OH)2 + OH-)

• [Zn(NH3)4] 2+ tetramminezinc ion (Zn2+ + NH3)

• [Cu(NH3)4]2+ tetramminecopper(II) ion (Cu2+ + NH3)

• [Cd(NH3)4] 2+ tetramminecadmium(II) ion (Cd2++ NH3)

• [FeSCN] 2+ thiocyanoiron(III) ion (Fe3+ + SCN-)

• [Ag(CN)2]- dicyanoargentate(I) ion (Ag+ and CN-)

Adding an acid to a complex ion will break it up. If HCl is added to a silver Complex, AgCl(s) is formed.

If an acid is added to an ammonia complex, NH4+ is formed.

Types of Complex Ion

• Complexation of a soluble salt

• Complexation of an insoluble salt

• Destruction of a complex by acid/base neutralization

– Acids destroy complex ions!

Complex Ion Practice

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

• 2. An excess of nitric acid solution is added to a solution of tetraaminecopper(II) sulfate.

• 3. Dilute hydrochloric acid is added to a solution of diamminesilver(I) nitrate.