Types of Reactions

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Chemical Reactions
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• Chemical reactions occur when bonds between the
  outermost parts of atoms are formed or broken

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• Chemical reactions involve changes in matter, the
  making of new materials with new properties, and
  energy changes.

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• Symbols represent elements, formulas describe
  compounds, chemical equations describe a chemical
  reaction

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• Items to the LEFT of the arrow in a chemical
  equation are called
• REACTANTS.
• 2Na Cl2 2NaCl

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• Items to the right of the
• arrow are called
• PRODUCTS.
• Ex 2Na Cl2 2NaCl

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Important NOTE

• No matter how many reactants and products are
  involved, all atoms present at the start of a
  reaction are present at the end.

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Conservation of Mass

• THE TOTAL MASS OF THE REACTANTS MUST EQUAL THE
  TOTAL MASS OF PRODUCTS.
• MATTER IS NEVER CREATED OR DESTROYED.

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Coefficient

• A number that tells how many molecules of a
  substance are involved in a
• chemical reaction.
• A coefficient of 1 is not written.

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Subscripts

• A subscript indicates how many atoms of an
  element are in a compound
• Ex. H2SO4
• H 2 S 1 O 4

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Subscripts vs. Coefficients
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Symbols

• -- used to separate two reactants or
  products.
• (yields) Separates reactants and
  products.

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Exothermic

• Reactions that release heat.

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Endothermic

• Reactions that absorb heat.

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Catalyst

• A substance that speeds up chemical reactions.

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Inhibitor

• A substance that slows down a chemical reaction.

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Types of Reactions
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Combustion

• Reactions that have hydrocarbons (CH4) and oxygen
  as reactants, and carbon dioxide and water as
  products.

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Example

• C3H8 5O2 ? 3CO2 4H2O

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Synthesis Reactions
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Examples

• 2Na Cl2 2NaCl
• Na2O CO2 Na2CO3

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Decomposition Reactions

• Starts with one reactant and ends with 2 or more
  products.

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Examples

• 2KClO3 2KCl 3O2
• 2NaCl 2Na Cl2

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Single Replacement Reactions

• One compound and a free element that recombine to
  yield a new compound and new free element.

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Examples

• Fe CuSO4 Cu FeSO4
• 2Na 2HCl H2 2NaCl

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Double Replacement Reactions

• Starts with 2 compounds as reactants. These
  recombine to form 2 new compounds as products.

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Examples

• NaCl AgNO3 NaNO3 AgCl
• KOH HNO3 HOH KNO3

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Let's Practice!
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C O2 -----? CO2
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2NaCl ? 2Na Cl2
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FeCl2 K2S ? FeS 2KCl
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C2H4 3O2 ? 2CO2 2H2O
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2AlCl3 3Na2CO3 ? Al2(CO3)3 6NaCl
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CS2 3O2 ? CO2 2SO2
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3Fe 4H2O ? Fe3O4 4H2
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2AlCl3 ? 2Al 3Cl2
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2Na H2SO4 ---gt Na2SO4 H2
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2Cr 3O2 ? 2CrO3