Chemical Reactions

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Chemical Reactions

• Chapter 16

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How do you know a Chemical Reaction happened?
- Color Change
- Heat Change
- Gas produced
- Precipitate formed
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What are the Parts Of A Chemical Reaction?

• Reactants
• Substances that interact with each other.
• On the left side of the arrow in chemical
  equation.

Reactants
Products
?
Zn 2HCl
ZnCl H2

• Products
• New substances formed during a reaction.
• On the right side of the arrow in chemical
  equation.

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What are the Parts Of A Chemical Equation?

• Chemical Symbols
• Identifies the elements involved
• Subscripts
• The small numbers to the lower right of chemical
  symbols. Subscripts represent the number of atoms
  of each element in the molecule.
• Coefficients
• The large numbers in front of chemical formulas.
  Coefficients represent the number of molecules of
  the substance in the reaction.
• Other Symbols ?(Read as Yields)

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Subscript
Coefficient
ZnCl H2
Zn 2HCl
?
Reactants
Products
Yields
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There are five General Types Of Reactions

• Synthesis
• Decomposition
• Single Displacement
• Double Displacement
• Combustion

Synthesis
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General Types Of Reactions
Synthesis
Two or more substances combine to form another
more complex substance The generalized formula
for this reaction is Element Element ?
Compound, or
A B ? AB
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General Types Of Reactions
Synthesis
Examples of Synthesis Reactions
2H2 O2 ? 2H2O 2Na Cl2 ? 2NaCl
A B ? AB
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General Types Of Reactions
Decomposition

• The opposite of synthesis reaction
• One substance breaks down into two or more
  simpler substances
• The generalized formula for this reaction is
  Compound ? Element Element, or

AB ? A B
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General Types Of Reactions
Decomposition
Examples of Decomposition Reactions
2H2O ? 2H2 O2 H2CO3 ? H2O CO2
AB ? A B
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General Types Of Reactions
Single-Displacement

• Occurs when one element replaces another element
  in a compound
• The generalized formula for this reaction is
  element compound ? compound element, or

A BC ? AC B
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General Types Of Reactions
Single-Displacement
Examples of Single-Displacement Reactions
2Na 2H2O ? 2NaOH H2 Zn 2HCl ? ZnCl2 H2
A BC ? AC B
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General Types Of Reactions
Double-Displacement

• Two different atoms in two different compounds
  exchange places
• The generalized formula for this reaction is
  compound compound ? compound compound, or

AX CY ? AY BX
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General Types Of Reactions
Double-Displacement
Examples of Double-Displacement Reactions
AgNO3 NaCl ? AgCl NaNO3 MgCO3 2HCl ?
MgCl2 H2CO3
AB CD ? AC BD
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General Types Of Reactions
Combustion

• A hydrocarbon reacts with oxygen
• The products of combustion are always water and
  carbon dioxide
• The generalized formula for this reaction is
  hydrocarbon oxygen ? water carbon dioxide

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General Types Of Reactions
Combustion
Examples of Combustion Reactions
CH4 2O2 ? CO2 2H2O C7H16 11O2 ? 7CO2
8H2O