Chemical Reactions

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Chemical Reactions
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Chemical Reactions

• Definition The process of when one or more
  substances undergo change to produce one or more
  different substances.
• B. Examples
• gas and oxygen producing carbon dioxide and water
• water and iron producing rust
• baking powder and water to form a carbon dioxide
• chlorophyll and sunlight resulting in leaf color

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C. 4 Clues to a Chemical Reaction

• Gas formation - appearance of bubbles
• Examples - Bubbling of alka seltzer, hydrochloric
  acid and limestone, baking (rise of baking goods)
• Solid formation precipitate forms in liquid
• 3. Color change
• Examples - bleach on clothes, hair dye, leaves
• 4. Energy change
• Examples - batteries converting to light energy,
  food digestion, any burning object such as a lit
  match

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Writing Formulas (p31) 1. Determine if the
bond is covalent or ionic Ionic -metal and
nonmetal Covalent - two nonmetals prefixes
in name
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2. Covalent Compounds

• 2 nonmetals
• prefixes in compound names tell how many of that
  element are in a formula write the prefix as a
  subscript with the element it appears with

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Prefixes for Covalent compounds

• mono 1
• di 2
• tri 3
• tetra 4
• penta 5

• hexa 6
• hepta 7
• octa 8
• nona 9
• deca - 10

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• examples of covalent formulas
• 1. carbon monoxide
• 2. phosphorus trichloride
• 3. sulfur dioxide

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examples of covalent formulas 1. carbon
monoxide CO 2. phosphorus trichloride
PCl33. sulfur dioxide SO2
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3. Ionic Compounds

• a. metal and nonmetal
• b. Determine oxidation numbers of
• each ion by using the periodic
• table (ch 1)
• c. Switch the oxidation numbers and
• use them as subscripts
• 1. Do not write any 1s
• 2. Reduce/rename subscripts if
• possible to simplest terms

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d. Examples of ionic formulas

• 1. aluminum oxide
• 2. calcium iodide
• 3. calcium oxide

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d. Examples of ionic formulas

• 1. aluminum oxide
• Al2O3
• 2. calcium iodide
• CaI2
• 3. calcium oxide
• CaO

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• E. Balancing Chemical Equations
• 1. Parts of an equation (p32)
• Reactants ? Products
• 2H2 O2 ? 2H2O
• 2. How to balance an equation (p34)
• count atoms of each element
• add coefficients
• add coefficients to low number of atoms
• only add coefficients to front of atoms/molecules
• recount
• repeat as needed

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• Law of Conservation of Mass states that mass is
  not created or destroyed during a chemical
  reaction or physical/chemical changes
• Balanced equations are an example.
• Lab proof example
• vinegar baking soda ? gas liquid Mass
  before reaction Mass after reaction

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F. 4 Types of Chemical Reactions

• Synthesis reactants combine to form a substance
• SO3 H20 H2SO4
• 2. Decomposition reactant breaks down to
  separate substances
• 2KClO3 2KCl 3O2
• Single Replacement one element changes places
  to join with another
• 3Zn 2FeCl3 3ZnCl2 2Fe
• Double Replacement two elements change places
• HCl KOH KCl H20

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G. 4 Factors Affect Reaction Rate

• Temperature
• ? temperature reaction speeds up
• ? temperature reaction slows down
• 2. Concentration
• ? concentration reaction speeds up
• ? concentration reaction slows down
• Surface Area
• ? surface area reaction speeds up
• ? surface area reaction slows down
• 4. Presence of catalyst or inhibitor
• catalyst speeds up reaction
• inhibitor slows down reaction

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Additional notesCounting Atoms

• Write each element symbol.
• Count the number of atoms of each element.
• No subscript 1 atom of the element
• Subscript tells how many atoms of the symbol
  before the number
• example H20 has 2 H atoms and 1 Oxygen
  atom
• Coefficient tells how many molecules of a
  formula are present (multiply the coefficient
  through the formula stop at signs or arrows)
• example 2H20 has 4 H and 2 O atoms