Types of Chemical Rxns

Composition (Combination) Rxns Two or more substances react to form a single, more complex substance. Examples: 2 Hg + O2 2HgO Sn + O2 SnO2 Movie of Potassium + Bromine

Decomposition Reactions A Complex Substance is Broken Down (usually by heating) into 2 or more smaller substances Examples MnO2 2 KClO3 + heat 2 KCl + O2 3 ªH BaCl2  2H2O BaCl2 + 2H2O Movie of Nitrogen TriIodide

Single Replacement Rxns A single element takes the place of another element in a compound Examples: Zn + HCl 2 H2 + ZnCl2 Cu + AgNO3 2 2 Ag + Cu(NO3)2 Movie of Thermite Reaction

Double Replacement Rxn The ions in two aqueous compounds Aswap partners@ Examples: AgNO3(aq) + NaCl(aq) AgCl(9) + NaNO3(aq) Calcium chloride + Potassium Nitrate Potassium chloride + Calcium nitrate See formula Movie of sodium iodide + lead(II) nitrate

CaCl2(aq) + KNO3(aq) 2 2 KCl(aq) + Ca(NO3)2(s) Back

A hydrocarbon reacts with oxygen to produce water and carbon dioxide Combustion Rxns A hydrocarbon reacts with oxygen to produce water and carbon dioxide Usually used for the large amount of heat given off! Balancing Tip: Do carbon 1st, then hydrogen, then oxygen Examples: CH4 + O2 2 2 H2O + CO2 + heat C2H5OH + O2 3 3 H2O + CO2 + heat 2

Combustion Rxns Hydrocarbon Hydrocarbon Hydrocarbon Hydrocarbon Most reactions that we think of as ‘burning’ a fuel are combustion reactions 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 Hydrocarbon Hydrocarbon Hydrocarbon Hydrocarbon Hydrocarbon

Some downsides to combustion reactions: 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

Some downsides to combustion reactions: 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)

Some downsides to combustion reactions: Combustion Rxns Some downsides to combustion reactions: Combustion will be “incomplete” when not enough oxygen is present Incomplete combustion results in CO, Carbon (soot), and nitrous oxides CO is poisonous Nitrous oxides are bad for the environment (acid rain, smog)

None of these “fixes” cuts 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

Identify each reaction type + + B) + O2 C H H C O2 C) O + + 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 Rxns Answers 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