1. Chapter 8 Chemical Reactions
Chemistry by Addison - Wesley

2. 8.1 Describing Chemical Change
Word Equations
In a chemical reaction, one or more substances change into one or more new substances
Reactants Products
Important to note that in a chemical reaction the atoms are neither created or destroyed; just rearranged

3. Chemical Equations
Chemical equation is similar to a word equation only chemical symbols represent substances
Skeleton equation represents the compounds without a quantity
State of matter can also be added to a skeleton equation
H2 (g) + O2 (g) H2O (l)

4. Balancing Equations Rules for Balancing Equations
Determine the correct formulas for the reaction
Write the formula with the reactants on the left and the products on the right
Count the number of atoms of each element on each side
Balance the elements one at a time using coefficients
Check each atom to make sure that it is balanced
Make sure the coefficients are in the lowest possible ratio

5. 8.2 Types of Chemical Reactions
Classifying reactions
Five Categories
Synthesis
Decomposition
Single-displacement
Double-displacement
Combustion

6. Synthesis Reactions
In a synthesis reaction, two or more substances combine to form a single substance
Two or more reactants
One product
H2 + O2 -> H2O

7. Decomposition Reactions
In a decomposition reaction, one substance breaks down into two or more substances
One Reactant
Two or more products
H2O -> H2 + O2
Often require heat or some sort of energy source to break down bonds in the compound

8. Single-Displacement Reactions
In a single-displacement reaction, one element replace another in a compound
Two reactants
Two products
Na + HCl -> H2 + NaCl
Normally, the replacement occurs at the cation spot

9. Double-Displacement Reactions
In a double-displacement reactions, two compounds exchange cations
Two reactants
Two products
NaOH + HCl -> H(OH) + NaCl
In most cases, one of the following will occur in a double-replacement reaction: 1) a precipitate forms, 2) a gas forms, or 3) a molecular compound forms

10. Combustion Reactions
In combustion reactions, a compound reacts with oxygen often to produce heat or light
One of the reactants will always be oxygen
A hydrocarbon is often the other reactant
Combustion of a hydrocarbon will produce H2O and CO2
C2H6 + O2 -> H2O + CO2 + heat

11. 8.3 Reactions in Aqueous Solutions
Net Ionic Equation
In an aqueous solution, compounds ionize into solution
Ions that are on both sides of the equation are called spectator ions
These ions cancel out of the equation

12. Predicting the Formation of a Precipitate
Solubility Rules for Ionic Compounds
Salts of alkali metals and ammonia - soluble (exceptions some lithium compounds)
Nitrate salts and chlorate salts - soluble (few exceptions)
Sulfate salts - soluble (Compounds of Pb, Ag, Hg, Ba, Sr, and Ca are exceptions)
Chloride salts - soluble (Ag and some Hg and Pb are exceptions)
Carbonates, phosphates, chromates, sulfides, and hydroxides - insoluble (Alkali metals and ammonia)