Chemical Reactions

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Chemical Reactions

• There are thousands of different chemical
  reactions that can take place in nature and in
  industrial processes
• It would be difficult to memorize all of them!
• By classifying reactions, we can predict the
  products that will form

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Types of Reactions

• These are the types of chemical reactions we will
  talk about
• Synthesis reactions
• Decomposition reactions
• Single displacement (replacement) reactions
• Double displacement(replacement) reactions
• Combustion
• You need to be able to identify the type of
  reaction and predict the product(s)

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Steps to Writing ReactionsStep 1

• Identify the type of reaction from clues that are
  available. Write a word equation.
• Example The combustion of methane gas in air
  forms water and carbon dioxide.
• Word equation
• Methane oxygen ? water carbon dioxide

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Step 2

• Write a generic equation following the rules from
  Reaction Types.
• Write the reactants and products using
  appropriate symbols and formulas.
• Balance charges for ionic compounds using the
  Common Ion Chart or Periodic Table.
• Dont forget diatomic elements! (BrINClHOF).
• Example
• Methane oxygen ? water carbon dioxide
• CH4 O2 ? H2O CO2

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Step 3

• Balance the equation by adjusting the
  coefficients.
• Example CH4 O2 ? H2O CO2
• Balanced CH4 2O2 ? 2H2O CO2

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Step 4

• Confirm that the equation is balanced by checking
  the number of atoms of each element on both sides
  of the equation.
• Example CH4 2O2 ? 2H2O CO2
• Reactants Products
• 1C 1C
• 4H 4H
• 4O 2O 2O 4O
• This equation is balanced!

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1. Synthesis reactions

• Synthesis reactions occur when two substances
  (sometimes elements) combine and form a compound.
  (Sometimes these are called combination or
  addition reactions.)
• reactant reactant ? 1 product
• Basically A B ? AB
• Example 2H2 O2 ? 2H2O
• Example C O2 ? CO2

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Synthesis Reactions

• Here is another example of a synthesis reaction

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Practice

• Predict the products. Write and balance the
  following synthesis reaction equations.
• Sodium metal reacts with chlorine gas
• Na(s) Cl2(g) ?
• Solid Magnesium reacts with fluorine gas
• Mg(s) F2(g) ?
• Aluminum metal reacts with fluorine gas
• Al(s) F2(g) ?

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2. Decomposition Reactions

• Decomposition reactions occur when a compound
  breaks up into the elements or in a few to
  simpler compounds
• 1 Reactant ? Product A Product B
• In general AB ? A B
• Example 2 H2O ? 2H2 O2
• Example 2 HgO ? 2Hg O2

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Decomposition Reactions when heated

• Metallic Carbonates give off metallic oxide and
  Carbon Dioxide Li2CO3 ? Li2O CO2
• Metallic Hydroxides give off metallic oxide and
  water Ba(OH)2 ? BaO H2O
• Metallic Chlorates give off metallic chloride and
  O2 2 NaClO3 ? 2 NaCl 3 O2
• Mineral Acids make water and nonmetal oxide
  H2CO3 ? H2O CO2
• Metal Oxides release O2 2PbO2 ? 2PbO O2
• Electrolysis breaks compounds into elements
  2KCl ? 2K Cl2

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2. Decomposition Reactions

• Another view of a decomposition reaction

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3. Single Replacement Reactions A BX ? B AX

• Active Metals replacing metals forming a
• salt. (Check the Activity Series) Na gt Ag
• Na AgNO3 ? Ag NaNO3

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More Single Replacement Reactions

• Very Active Metals react w/ water releasing H2
  and metallic hydroxide
• (check Activity Series)
  2K 2H2O ? H2 2KOH
• Metals and Acids form H2 and salts
• Zn 2 HCl ? H2 ZnCl2
• Halogen-Halide Replacement (check
  Activity Series)
• F2 2RbBr ? Br2 2RbF
  

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Single Replacement Reactions

• Aluminum metal reacts with Copper II Nitrate
• Al Cu(NO3)2 ?

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4. Double Replacement Reactions

• Double Replacement Reactions occur when a metal
  replaces a metal in a compound and a nonmetal
  replaces a nonmetal in a compound
• Compound compound ? product product
• AB CD ? AD CB

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Double Replacement Reactions

• Think about it like foiling in algebra, first
  and last ions go together inside ions go
  together
• Example
• AgNO3(aq) NaCl(s) ? AgCl(s) NaNO3(aq)
• Another example
• K2SO4(aq) Ba(NO3)2(aq) ? KNO3(aq) BaSO4(s)

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Practice

• Predict the products. Be sure to check the
  charges. Balance the equation
• HCl(aq) AgNO3(aq) ?
• CaCl2(aq) Na3PO4(aq) ?
• Pb(NO3)2(aq) BaCl2(aq) ?
• FeCl3(aq) NaOH(aq) ?
• H2SO4(aq) NaOH(aq) ?
• KOH(aq) CuSO4(aq) ?

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5. Combustion Reactions

• Combustion reactions occur when a hydrocarbon
  reacts with oxygen gas.
• This is also called burning!!! In order to burn
  something you need the 3 things in the fire
  triangle1) Fuel (typically hydrocarbon)2)
  Oxygen (supports combustion)3) Ignition energy
  (spark or heat)

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Combustion Reactions

• In general CxHy O2 ? CO2 H2O
• Products in combustion are ALWAYS carbon dioxide
  and water. (although incomplete burning does
  cause some by-products like carbon monoxide)
• Combustion is used to heat homes (Methane, CH4)
  and run automobiles (Octane, C8H18)

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Combustion

• Example
• C5H12 O2 ? CO2 H2O
• Write the products and balance the following
  combustion reaction
• C10H22 O2 ?
  
  
  
  
  
  
  
  
  
  
  
  

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Mixed Practice

• State the type, predict the products, check the
  charges and balance the following reactions
• BaCl2 H2SO4 ?
• C6H12 O2 ?
• Zn CuSO4 ?
• Cs Br2 ?
• FeCO3 ?

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Solubility Table
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Determining Reaction Types
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Identifying Reactions and Predicting Products
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Identifying Reactions and Predicting Products
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Identifying Reactions and Predicting Products