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Types of Chemical Rxns. Composition (Synthesis) Rxns. Two or more substances react to form a single, more complex substance. Examples:. 2 Hg + O 2. 2HgO. 2Ag + S. Ag 2 S. Movie of Potassium + Bromine. Decomposition Reactions. A Complex Substance is Broken Down
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Composition (Synthesis) Rxns Two or more substances react to form a single, more complex substance. Examples: 2 Hg + O2 2HgO 2Ag + S Ag2S Movie of Potassium + Bromine
Decomposition Reactions A Complex Substance is Broken Down (usually by heating) into 2 or more smaller substances Which Side does energy term go on? ____thermic endo Examples MnO2 KClO3 + heat 2 2 KCl + O2 3 ªH BaCl2 + 2H2O BaCl2 2H2O MnO2 2 + heat H2O (l) + O2(g) H2O2 (aq) 2 Movie of Nitrogen TriIodide
Single Replacement Rxns A single element takes the place of another element in a compound Examples: Zn + HCl H2 + ZnCl2 2 2 Cu + AgNO3 2 Ag + Cu(NO3)2 Movie of Thermite Reaction
Double Replacement RxnSometimes called Exchange or Metathesis Rxns The ions in two aqueous compounds swap partners Examples: AgCl(9) + NaNO3(aq) AgNO3(aq) + NaCl(aq) Calcium chloride + Potassium Nitrate Potassium chloride + Calcium nitrate See formula Movie of sodium iodide + lead(II) nitrate
2 2 CaCl2(aq) + KNO3(aq) KCl(aq) + Ca(NO3)2(s) Back
Combustion Rxns A hydrocarbon reacts with oxygen to produce water and carbon dioxide Usually used for the large amount of heat given off! ___thermic Balancing Tip: Do carbon 1st, then hydrogen, then oxygen Examples: exo 2 CH4 + O2 2 H2O + CO2 + heat C2H5OH + O2 3 3 H2O + CO2 + heat 2
Combustion Rxns Most reactions that we think of as ‘burning’ a fuel are combustion reactions Hydrocarbon Hydrocarbon Hydrocarbon Hydrocarbon Hydrocarbon • Examples: • Burning a log of Wood to heat your s’mores • Burning Coal to heat water to create electricity at a power plant • Grilling with Propane to heat your hot dog • Burning Gasoline in your car to heat the air and push pistons • Burning Oil in your furnace to heat your house
Combustion Rxns Some downsides to combustion reactions: • Fossil Fuels are non-renewable resources • We are using them much faster than they are being produced • Eventually, we will run out of fossil fuels
Combustion Rxns Some downsides to combustion reactions: CO2 is a greenhouse gas and increasing CO2 levels contributes to global warming – (others are methane, water vapor, ozone, nitrous oxide) Our widespread burning of fossil fuels over the last hundred years has increased the earth’s CO2 levels
Combustion Rxns Some downsides to combustion reactions: • Combustion will be “incomplete” when not enough oxygen is present • Complete Combustion • Hydrocarbon + O2 • Incomplete combustion results in CO, Carbon (soot), and nitrous oxides • Hydrocarbon + O2 C + CO +H2O + CO2 • CO is poisonous • Nitrous oxides are bad for the environment (acid rain, smog) + CO2 H2O
Combustion Rxns What can be done? • Incomplete combustion can be improved by better designed burners / engines • Catalytic converters in vehicle reduce CO • “Scrubbers” placed in industrial exhaust systems can reduce nitrous oxides and CO None of these “fixes” cuts down or removes CO2 emissions Balancing Combustion
Identify each reaction type (sr, dr, comp , decomp, combust) A) + + + B) C O2 H O2 C H O + C) + D) + + + E)
A Closer Look: Composition Rxns • Aluminum + oxygen • Calcium oxide + water • Sulfur + oxygen
More Composition Rxns • Sn + O2 -----> • Sodium + chlorine----> • SO3 + H2O --------> • Lithium oxide + water--> • Silicon + oxygen
More Composition RxnsAnswers • Sn + O2 ----->SnO2 • 2Na + Cl2 ---> 2NaCl • SO3 + H2O --------> H2SO4 • Li2O + H2O ------> 2LiOH • Si + O2 -----> SiO2
Decomposition Rxns • CuSO4 5H2O • NaHCO3 • HNO3
More Decomposition Rxns • Na2CO3 ----> • MgO -----> • MgSO4 7H2O ----> • Sr(NO3)2 ----> • H2CO3 ---->
More Decomposition Rxns (Answers) • Na2CO3 ----> Na2O + CO2 • 2MgO -----> 2Mg + O2 • MgSO4*7H2O ----> MgSO4 + 7H2O • Sr(NO3)2 ----> Sr(NO2)2 + O2 • H2CO3 ----> H2O + CO2
Warm-Up: Complete and Balance C2H6 + O2 CO2 + H2O 2 3 7 oxygens Can I get 7 Oxygens here?
Balancing Combustion Rxns 5 PBJ Sandwiches = ____ slices of bread 10
Balancing Combustion Rxns 5 half PBJ Sandwiches = ____ slices of bread 5 5 pairs x ½ = 5 singles
Balancing Combustion Rxns 5 half O2 molecules = ____ atoms of O 5 5 pairs x ½ = 5 singles
Balancing Combustion Rxns 7/2 O2 molecules = ____ atoms of O 7 7 pairs x ½ = 7 singles
7 2 Warm-Up: Complete and Balance C2H6 + O2 CO2 + H2O 2 3 7 oxygens Total of 7 O’s
Your Turn: • Complete # 10-12 on Page 14 in your packet