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Chemistry Unit 6 Reactions
Chemical Reactions
8-1
Chemical equations: represents with symbols and formulas the identities and relative amounts of the reactant and the products in a chemical reaction.


Reactants     ®    Products

Indications of chemical change or reaction
   production of heat and or light
   production of a gas
   production of a solid (precipitate)

Know symbols used in chemical equations on pg. 246 table 8-2

Significance of a Chemical reaction
Coefficients represent relative amounts not absolute (smallest whole number ratio)

ex:

The masses of the reactants and products can be calculated from the equation coefficients.

ex:

The reverse reaction yields the same amounts of substances the forward reaction yields.

ex:

Balancing Chemical Equations (to satisfy the law of conservation of mass)
Write correct formulas for the reactants and the products
Balance different types of elements one at a time.
Balance the atoms that appear only once on each side of the equation
Balance polyatomic ions that appear unchanged on both sides of the equation
Balance H and O atoms after atoms of all other elements have been done.
Count atoms to be sure that each side balances with each other.


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ex:

ex:

8-2
Types of Chemical Reactions
1.  Synthesis:     A  +  B  ®  AB
2.  Decomposition:  AB  ®   A  +  B
3.  Single replacement:  A   +  BD  ®  AD  +  B  ( CATIONIC)     ;  X   +  YZ  ®   YZ  +  X  ( ANIONIC)
8-3
Use activity series of elements given to you by state
4.  Double replacement: AB  +  CD  ®  AD  +  CB
5.  Combustion: hydrocarbon  +  02  ®  CO2   +  H2O
    Complete:  only carbon dioxide and water produced
    Incomplete:  carbon dioxide, carbon monoxide and water produced.