III Equation Problems

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III Equation Problems

• A What does an equation represent?
• Represents chemical change
• Made up reactants and products
• Reactants
• starting materials
• left side
• Products
• end results
• right side
• K O2 ? K2O

Reactants
Products
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• B Balancing Equations
• Law of Conservation of Mass
• Matter cannot be created or destroyed
• Reactants equal products
• Use coefficients to balance equation
• K O2 ? K2O
• 1 K 2
• 2 O 1
• 4 K O2 ? 2 K2O

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• HgO ? Hg O2
• 1 Hg 1
• 1 O 2
• 2 HgO ? 2 Hg O2

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• CaCl2 AgNO3 ? Ca(NO3) 2 AgCl
• 1 Ca 1
• 2 Cl 1
• 1 Ag 1
• 1 NO3 2
• CaCl2 2 AgNO3 ? Ca(NO3) 2 2 AgCl

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• C2H4 O2 ? CO2 H2O
• 2 C 1
• 4 H 2
• 2 O 3
• C2H4 3 O2 ? 2 CO2 2 H2O

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• C2H6 O2 ? CO2 H2O
• 2 C 1
• 4 H 2
• 2 O 3
• 2 x (C2H6 3.5 O2 ? 2 CO2 3 H2O)
• 2 C2H6 7 O2 ? 4 CO2 6 H2O

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• C. Classification
• 5 Basic Types of Reactions
• Synthesis
• Decomposition
• Single Replacement
• Double Replacement
• Combustion
• 1. Synthesis
• 2 substances make 1 substance
• 2 reactants---1 product
• K O2 ? K2O

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• 2. Decomposition
• 1 compound makes 2 substances
• 1 reactant---2 products
• 2 HgO ? 2 Hg O2
• 3. Single Replacement
• 1 element and 1 compound become 1 new element and
  1 new compound
• 2 reactants---2 products
• Ca 2 AgNO3 ? Ca(NO3) 2 2 Ag

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• 4. Double Replacement
• 2 compounds make 2 new compounds
• 2 reactants---2 products
• CaCl2 2 AgNO3 ? Ca(NO3) 2 2 AgCl
• 5. Combustion
• 1 organic compound and oxygen make CO2 and H2O
• 2 reactants---2 products
• C2H4 3 O2 ? 2 CO2 2 H2O

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D. Use of Equations

• Shows what reacts (qualitative) and how much
  reacts (quantitative)
• Ex. 2 Na Cl2 ? 2 NaCl
• Qualatative
• Na reacts with Cl2 to make NaCl
• Quantitative
• 2 moles Na react with 1 mole Cl2 to make 2 moles
  NaCl
• How many moles of NaCl are made using 1.4 moles
  Cl2?
• Find ratio
• 12 or 21
• Multiply the given info by the ratio
• Get the given unit to cancel out
• 1.4 moles Cl2 x 2 moles NaCl 2.8 moles NaCl
• 
  1 mole Cl2

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• Ex. N2 3 H2 ? 2 NH3
• How many grams of NH3 are made using 12 g H2?
• Convert to moles
• Multiply the given info by the ratio
• Convert to grams
• 12g H2 x 1 mole H2 x 2 moles NH3 x 17g NH3
• 2g H2 3 moles H2
  1 mole NH3
• 
  68g NH3