Chemical Equations

1
Chemical Equations

• A chemical equation is a representation of a
  chemical reaction in which the reactants and
  products are expressed as formulas.
• Reactant Reactant ? Product
• Reactants are the substances that undergo the
  change.
• Products are the new substances formed.
• C O2 ? CO2
• Reactants ? Product

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2 3 5

• Antoine Lavoiser determined that the mass of the
  products is always equal to the mass of the
  reactants.
• The law of conservation of mass states that mass
  is neither created nor destroyed in a chemical
  reaction.
• In order to show mass is
• conserved an chemical
• equation must be balanced.

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Mole

• Because chemical reactions often involve large
  numbers of small particles, chemists use a
  counting unit called the mole to measure amounts
  of a substance.
• 1 mole 6.02 x 1023 atoms

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Types of Reactions

• A synthesis reaction is a reaction in which two
  or more substances form a single substance.
  (Simple ? Complex)
• A B ? AB

• A decomposition reaction is when a compound
  breaks down into two or more simpler substances.
  (Complex ? Simple)
• AB ? A B

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Types of Reactions II

• Single Replacement reaction in which one element
  takes the place of another element in a compound.
  (One person breaks up a couple and goes out with
  one of them. A BC? AC B

• Double Replacement reaction is one in which two
  different compounds exchange positive ions and
  form two new compounds.
• AB CD ? AD CB

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Types of Reactions

• Ca O CaO
• Br LiI LiBr I
• Al Fe(NO3)2 Al(NO3)3 Fe
• MgO HCl MgCl2 H2O
• C4H10 O2 CO2 H2O
• NH4NO2 NH3 H2O

• A combustion reaction is when a substance reacts
  rapidly with oxygen, often producing heat and
  light.
• Classify the different types of reaction

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Oxidation/Reduction

• A reaction in which a metal reacts with oxygen is
  called an Oxidation.
• This occurs when a metal losses its electrons
  and becomes a positive ion.

• Reduction is when a non-metal gains electrons.
• Oxidation and reduction always occur together.

8
Energy Changes

• Chemical energy is the energy stored in the
  chemical bonds of a substance.
• Breaking a chemical bond requires energy.
• During a chemical reaction, energy is either
  gained or released.

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In/Out

• Endothermic Reaction More energy is required to
  break the bonds in the reactants than is released
  by the formation of the products.
• Endo Enters
• Examples
• Alka-seltzer
• Ice packets
• Camera

• Exothermic Reaction the energy released as the
  products form is greater than the energy required
  to break the bonds.
• Exo Exit
• Examples
• Fire
• Digestion
• Hand warmers

10
Reaction Rate

• Reaction rates tell you how fast a reaction is
  going.
• Temperature Increasing the temperature
  generally increases the reaction rate.
• Stirring Increases the exposure of the reactant
  increases the reaction rate.

• Surface Area Increasing surface area increases
  the reaction rate.
• Concentration Increasing concentration
  increases the reaction rate.
• Catalyst A catalyst is a substance that affects
  the reaction rate with out being used up in the
  reaction.

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Equilibrium

• Equilibrium is a state in which the forward and
  reverse paths of a change take place at the same
  rate.
• A reverse reaction is a reaction in which the
  conversion of reactants into products and the
  conversion of products to reactants can happen
  simultaneously.
• Concentration, temperature and pressure can
  affect equilibrium.