CHAPTER 7.2: Chemical reactions involve a rearrangement of the ways atoms are grouped together.

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• CHAPTER 7.2 Chemical reactions involve a
  rearrangement of the ways atoms are grouped
  together.

• A chemical equation represents a chemical
  reaction.
• Reactants are shown to the left of an arrow.
• Products are shown to the right of the arrow.

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• In a chemical reaction atoms are not created or
  destroyed.

• All atoms present in the reactants must be
  accounted for in the products.
• Same number of each type atom on both sides of
  the arrow

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• Balancing a Chemical Equation CH4 O2 ? CO2 H2O

• Unbalanced equation

• Balancing the equation

• The balanced equation CH4 2O2 ? CO2
  2H2O

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• Physical states of compounds are often given in a
  chemical equation.

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• CHAPTER 7.3 A chemical reaction is balanced by
  using a systematic approach

• Write the formulas of the reactants and products
  to give the unbalanced chemical equation.
• Balance by trial and error starting with the most
  complicated molecule(s). Going back forth start
  with
• One-sies
• 2nd to last oxygens
• Last hydrogens
• When done, check to be sure the equation is
  balanced (same numbers of all types of atoms on
  the reactant and product sides).

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• Example  H2(g) O2(g) ? H2O(l)

• Hydrogen gas and oxygen gas combine to form
  liquid water.
• Balance by trial and error starting with the most
  complicated molecule(s).

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• Example 

• Hydrogen gas and oxygen gas combine to form
  liquid water.
• At the end check to be sure the equation is
  balanced (same numbers of all types of atoms on
  the reactant and product sides). 2H2(g)
  O2(g) ? 2H2O(l)
• END OF CHAPTER 7!

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CHAPTER 8 Section 8.1A. Predicting Whether a
Reaction Will Occur

• Four driving forces favor a chemical change.
• Formation of a solid
• Formation of water
• Transfer of electrons
• Formation of a gas

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B. Reactions in Which a Solid Forms

• A reaction in which a solid forms is called a
  precipitation reaction.
• Solid precipitate

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B. Reactions in Which a Solid Forms
What Happens When an Ionic Compound Dissolves in
Water?

• The ions separate and move around independently.

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B. Reactions in Which a Solid Forms
What Happens When an Ionic Compound Dissolves in
Water?

• K2CrO4(aq) Ba(NO3)2(aq) ? Products

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B. Reactions in Which a Solid Forms
How to Decide What Products Form

• Determine the possible products from the ions in
  the reactants.
• In our example
• K2CrO4(aq) Ba(NO3)2(aq) ? Products
• The possible ion combinations are

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B. Reactions in Which a Solid Forms
Solubility Rules
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B. Reactions in Which a Solid Forms
Using Solubility Rules

• Predicting Precipitates

• Soluble solid sol
• Insoluble solid insol
• Slightly soluble solid ss

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B. Reactions in Which a Solid Forms
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A. Reactions That Form Water Acids and Bases
Arrhenius Acids and Bases

• A strong acid is one in which virtually every
  molecule dissociates (ionizes) in water to an H
  ion and an anion.

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A. Reactions That Form Water Acids and Bases
Arrhenius Acids and Bases

• A strong base is a metal hydroxide that is
  completely soluble in water, giving separate OH?
  ions and cations.

• Most common ? NaOH, KOH

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A. Reactions That Form Water Acids and Bases
Arrhenius Acids and Bases

• The products of the reaction of a strong acid and
  a strong base are water and a salt.

• Salt ? Ionic compound metal nonmetal M
  X-
• -- Water formation equation
• H(aq) OH-(aq) ? H2O(l)
• Note The reaction of H and OH- is called
  an acid-base reaction.
• H ? acidic ion
• OH- ? basic ion

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B. Reactions of Metals with Nonmetals
(Oxidation-Reduction)

• Reactions between metals and nonmetals involve a
  transfer of electrons from the metal to the
  nonmetal.
• This is called an oxidation reduction reaction.

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A. Ways to Classify Reactions

• Driving forces for a reaction
• Formation of a solid
• AB CD ? AD CB
• Precipitation reaction
• Double displacement reaction
• Formation of water
• H(aq) OH-(aq) ? H2O(l)
• Acid-base reaction

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A. Ways to Classify Reactions

• Driving forces for a reaction

• Transfer of electrons

• Formation of a Gas

• A BC ? B AC
• Single replacement reaction

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B. Other Ways to Classify Reactions
Combustion Reactions

• Involve oxygen and produce energy so rapidly that
  a flame results
• Produces CO2 H2O
• Example
• CH4(g) 2O2(g) ? CO2(g) 2H2O(g)
• Special class of oxidation-reduction reactions

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B. Other Ways to Classify Reactions
Synthesis (Combination) Reactions

• A synthesis reaction is one in which a compound
  forms from simpler materials.
• One product, and two (or more) reactants
• Example
• C(s) O2(g) ? CO2(g)
• Special class of oxidation-reduction reactions

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B. Other Ways to Classify Reactions
Decomposition Reactions

• A decomposition reaction occurs when a compound
  is broken down into simpler substances.
• One reactant, and two (or more) products.
• Example
• 2H2O(l) ? 2H2(g) O2(g)

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B. Other Ways to Classify Reactions
Summary
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SUMMARY OF REACTION TYPES TO KNOW

• Double displacement reaction
• AB CD ? AD CB
• Acid-base reaction
• HX-(aq) MOH-(aq) ? MX- H2O(l)
• Single replacement reaction
• A BC ? B AC
• Combustion reaction
• CH4(g) 2O2(g) ? CO2(g) 2H2O(g)
• Synthesis reaction
• C(s) O2(g) ? CO2(g) one product
• Decomposition reaction
• one reactant 2H2O(l) ? 2H2(g) O2(g)