Chemical Reactions

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• Chemical Reactions Balancing Equations

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Chemical Reactions

• 2 Parts
• Reactants substances at the start
• Products substances at the end
• The reactants turn into the products.
• Reactants ? Products

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Equation Format

• means reacts with or and
• ? means yields or forms
• Reactants written on LEFT side
• Products written on RIGHT side

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In a Chemical Reaction

• The way atoms are joined is changed
• Atoms are neither created nor destroyed.
• This is the Law of Conservation of Matter
• Balanced Equation
• Each element has same of atoms on both sides of
  the equation.

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• C O2 CO2
• This equation is already balanced
• same number of atoms of each type of element on
  each side
• What if it isnt balanced already?

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If it is NOT Balanced Already

• C O2 CO

• This is called a skeletal reaction
• Shows all the reactants and products
• Does not show balanced quantities

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Cooking Analogy for Chemical Reactions

• Skeletal reaction
• Ingredients description of meal
• Balanced reaction
• Exact recipe

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Skeletal Reaction ? Balanced Equation

C
O
O

C
O

• Add molecules until there is an equal number of
  atoms on both sides.
• Use only molecules or atoms already in the
  formulas
• No new compounds used or created
• Start with the element you need more of!

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Skeletal Reaction ? Balanced Equation

C
O
O

C
O

• 1C O2 2C 2O
• The 2 subscript on Oxygen means there are 2 of
  them in the molecule.
• Still not balanced ? need 1 more C on the
  reactant side.

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C
C
O

O

O
C
O
2C O2 ? 2C
2O Equation 2C O2 ?
2CO
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C
C
O

O

O
C
O
2C O2 ? 2CO

• Coefficient
• Large Number left of the compound formula.
• Represents the number of molecules/atoms
• Helps to balance the equations
• makes of atoms on left side on right side

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• Coefficients Subscripts on the same molecule
• The numbers must be multiplied to determine the
  number of atoms of that element.

• 2C 2O2 ? 2CO2
• 2C 4O 2C 4O
• Notice the subscript only applies to the element
  it is next to!

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Exit Slip Questions

• What are the 2 parts that make up chemical
  equations?
• Products
• Balances
• Reactants
• Skeletons

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Exit Slip Questions

• How does the law of Conservation of Matter impact
  writing chemical equations?
• No impact
• It limits the reactants you can use
• It makes each element have the same of atoms on
  both sides of a balanced equation
• It limits the products you can make

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Exit Slip Questions

• Which of the following is true about balanced
  equations vs. skeletal equations?
• Theres no such thing as skeletal equations
• Balanced equations use different reactants
• Skeletal equations make different products
• They have the same reactants and products, but
  the amount of compounds differ

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Exit Slip Questions

• What do coefficients in chemical equations tell
  you?
• How many atoms are in a chemical compound
• The atomic mass of a chemical compound
• How many molecules are needed to balance a
  chemical equation
• Nothing - I wasnt paying attention