The main tasks of Chap 8

Sect 1 - Writing reactions from word problems – challengingSect 2 - Balance Equations—easiest Sect 3 - Classify Equations, Complete

Equations—challengingSect 4 – Write Net Ionic equations

Classifying Reactions

You will learn to recognize the different types of reactions AND

How to complete products (predict).

Combustion Reactions “Burning”

• Oxygen is a reactant.• Energy is producedCombustion of carbon compounds yield carbon dioxide(CO2) and water (H2O ).• Mg + O2 MgO• CH4 + O2 CO2 + H2O

Synthesis Reactions

Two or more elements or compounds combine to form ONE PRODUCT.• Mg + O2 MgO• H2 + O2 H2O• )()()( 4223 aqSOHlOHgSO

Decomposition Reactions

ONE REACTANT (compound) breaks into elements or smaller compounds.• H2O H2 + O2

• MgO Mg + O2

Displacement Reactions

• Also called Replacement reactions• Single Displacement/Replacement– Use the Activity series

• Double Displacement/Replacement– Precipitation Reactions• Use the Solubility Rules

– Acid Base Reactions

Single Displacement

Part of an ionic compound is removed and replaced by a new element.• ELEMENT + COMPOUND COMPOUND + ELEMENTThere are 2 subtypes of single replacement reactions.- Cationic replacement- Anionic replacement

Single Displacement subtype CATIONIC REPLACEMENT:

• If the Element is a Metal, it replaces the metal in the compound.

• Cu + AgNO3 Cu(NO3)2 + Ag

Single Displacement subtype:ANIONIC REPLACEMENT:

• If the Element is a Non-metal, it replaces the non-metal in the compound.

• Cl2 + NaBr NaCl + Br2

Single Replacement Rxns

• To determine if a Single Replacement Reaction really happens, use the ACTIVITY SERIES reference sheet.

• If an element is higher on the chart, it will become a compound.

• If the higher element is already in a compound, then NO reaction occurs

Double Replacement Rxns

• Two Ionic Compounds that exchange partners.

• XY + AB AY + XB

• Only Positive with Negative• Positive Ion listed first

Double Replacement Rxns

• To determine if the reaction occurs, use the SOLUBILITY RULES.

• A reaction occurs if a solid or water forms when two aqueous solutions of ionic compounds are mixed.

• If the products are both aqueous ionic compounds, then no reaction occurs.

Solubility Rules info.

• Soluble = dissolves in water = (aq) = clear

• Insoluble= doesn’t dissolve in water = SOLID = (s) = cloudy = precipitate = ppt

Section 4: Net Ionic Equations

• Three ways to write the same equation (usually with double replacement rxns):

• 1. Complete Molecular Equation• 2. Complete Ionic Equation• 3. Net Ionic Equation

Dissolving (aq) separates the ions

• NaCl (s) in water NaCl (aq)• NaCl (aq) means Na+(aq) + Cl- (aq)• The Ions move separately in solution.• In some equations we separate the ions and

write the charges.

Complete Molecular Eqn

• This is what we have been doing. Write the compounds with the ions together.

• Example: NaCl (aq) + AgNO3 (aq)

AgCl (s) + NaNO3(aq)

Complete Ionic Eqns

• Write the aqueous compounds as separate ions. Be sure to put the CHARGES ON THE IONS!

• Keep the solid(insoluble) or water molecules together.

• Example:

Na+ (aq) + Cl- (aq) + Ag+(aq) + NO3- (aq)

AgCl (s) + Na+(aq)+ NO3-(aq)

Net Ionic Equations• Take the Complete ionic equation and remove

any ion that is aqueous on both sides. These ions are called Spectator Ions.

OR• Find the Solid product or water, keep that part

AND keep the reactant ions that made the solid or water.

• Ex: Ag+ (aq) + Cl- (aq) AgCl(s)

Net Ionic Eqns with Acids and Bases( H+ and OH-)

When acids (HA) and Bases (ZOH) mix, the H+ and OH- combine to become H2O(l).

This is called a neutralization reaction.The water H2O(l) stays together like insoluble

solids. So you keep it in the Net Ionic equation.

Ex. H+ + OH- H2O

Example: Complete and Net Ionic Equations page 1

Cu(NO3 )2 (aq) + NaOH(aq) ????1) Write Complete Molecular Equation: Cu(NO3 )2 (aq) + NaOH(aq) Cu(OH)2 (s) + NaNO3 (aq)

2) Write Complete Ionic Equation: [separate all (aq), put charges on ions; keep solids together.]

Cu+2(aq) +2NO3 -1(aq) + 2Na+1 (aq) + OH-1 (aq)

Cu(OH)2 (s) + 2Na+1 (aq) + 2NO3 -1 (aq)

And then…

Example: Complete and Net Ionic Equations page 2

3) Write Net Ionic Equation: [eliminate spectator ions, keep ions that make solid, keep solids.]

Cu+2(aq) + OH-1 (aq) Cu(OH)2 (s)