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Chapter 8 Chemical Reactions

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Title: Chapter 8 Chemical Reactions


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
Examples
  • Turn to page 209

6
8.2 Types of Chemical Reactions
  • Classifying reactions
  • Five Categories
  • Combination
  • Decomposition
  • Single-replacement
  • Double-replacement
  • Combustion

7
Combination Reactions
  • In a combination reaction, two or more substances
    combine to form a single substance
  • Two or more reactants
  • One product
  • H2 O2 -gt H2O

8
Examples
  • Turn to page 214

9
Decomposition Reactions
  • In a decomposition reaction, one substance breaks
    down into two or more substances
  • One Reactant
  • Two or more products
  • H2O -gt H2 O2
  • Often require heat or some sort of energy source
    to break down bonds in the compound

10
Examples
  • Turn to page 216

11
Single-Replacement Reactions
  • In a single-replacement reaction, one element
    replace another in a compound
  • Two reactants
  • Two products
  • Na HCl -gt H2 NaCl
  • Normally, the replacement occurs at the cation
    spot

12
Examples
  • Turn to page 218

13
Double-Replacement Reactions
  • In a double-replacement reactions, two compounds
    exchange cations
  • Two reactants
  • Two products
  • NaOH HCl -gt 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

14
Examples
  • Turn to page 220

15
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 -gt H2O CO2 heat

16
Examples
  • Turn to page 221

17
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
  • Net Ionic Equation

18
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)
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