04 28 2014 Oxidation reduction reactions involve the transfer of electrons from 1 species to another we change the oxidation state Most energy related reactions are redox reactions Glucose O2 CO2 H2O energy Oxygen is a good oxidant usually involved in combustion Oxidation loss of electrons Reduction gaining electrons O I L R I G We keep track of the elements by assigning oxidation numbers General Rules Specific Rules 1 Pure elements are 0 Na O2 He Cl2 Li 2 Charge of a single atom oxidation number Na 1 Mg2 2 3 The sum of all oxidation numbers total charge of molecule 1 Hydrogen 1 with a nonmetal HCl HF CH4 1 with a metal or boron LiH BH3 2 Oxygen 2 in most compounds CO2 H2O CO 1 in peroxides 3 Halogens 1 usually Can be different with O or other halogens above them Fluorine is always 1 4 Everything else is figured out by arithmetic Example Ammonium Nitrate NH4NO3 H 1 N 3 What happens when we put Mg Zn and Cu in acid Activity Series A metal higher in the series will displace an element below it in the series They put zinc on steel ships so seawater doesn t corrode it React with acid not water Electrons flow from more active metals to less active metals If a metal is above H2 on the series it will react w acid to form Hydrogen gas 04 30 2014 A properly balanced reaction means both mass and charge are balanced We need to keep track of atoms and electrons Sometimes the solvent is involved in the reaction Another way to look at redox reactions is to separate them Fe2 MnO4 Fe3 Mn2 acidic solution 2 half reactions Fe2 Fe3 iron is oxidized MnO4 Mn2 manganese is reduced Because there is an O we can add water on one side to balance it out Balance H with H Use electrons to balance charges For balancing in basic conditions add OH to get rid of H add equal numbers to both sides 05 02 2014 1 FeCl3 2 NO2 Cl 1 Fe 3 N 4 O2 2 H2SO4 H2 1 S 6 O4 2 2 Al MnO4 MnO2 Al OH 4 Al Al OH 4 4H2O Al Al OH 4 4H 3e MnO4 MnO2 4H MnO4 MnO2 2H2O 3e 4H MnO4 MnO2 2H2O 2H2O Al MnO4 Al OH 4 MnO2 3 Cl2 Cl ClO Cl2 Cl 2e Cl2 2Cl Cl2 ClO 2H2O Cl2 2ClO 4H 2e 2H2O 2Cl2 2Cl 2ClO 4H 4 NO2 Al NH3 AlO2 NO2 NH3 7H NO2 NH3 2H2O 6e 7H NO2 NH3 2H2O Al AlO2 2H2O Al AlO2 4H 2 2H2O Al AlO2 4H 3e OH H2O 2Al NO2 NH3 2AlO2 5 MnO4 S2 MnS S 5 S2 S 2e 8H S2 MnO4 MnS 4H2O 2 5e 8H S2 MnO4 MnS 4H2O 7S2 8H2O 2MnO4 5S 2MnS 16OH 6 CN MnO4 CNO MnO2 3 H2O CN CNO 2H 2e 4H MnO4 MnO2 2H2O 3e 2 4H 3e MnO4 MnO2 2H2O 3CN 2H 2MnO4 3CNO 2MnO2 2OH 2CN H2O 2MnO4 3CNO 2MnO2 2OH 05 05 2014 The Atmosphere an Pressure The earth s atmosphere is 50 km thick and is composed of location temperature weather altitude amount of air 78 nitrogen 21 oxygen and trace gases Ar CO2 H2O Ch4 etc The weight of these gases exert pressure because gravity pulls it down Pressure depends on Sea level vs Mountain level P sub gas 0 Characteristics of gases Highly compressible Thermally expandable Low viscosity easy to pour Low density Infinity miscible can mix together in any proportion Pressure is force per unit area P F A SI units N m 2 the Pascal pa Standard atmospheric pressure 1 atm 760 mm Hg P h x g x d P atmospheric pressure For Mercury Barometers Sea Level 1 atm 760 mmHg Units of Pressure and Converting The volume of gas decreases when pressure is applied Volume of gas decreases in cold and increases in hot Volume of gas increases when you add more Pressure goes up if you heat it up 1 atm 760 mmHg 760 torr 14 7 psi h x g x d Force of hg in a cross section h height g gravity d density atm mmHg torr 05 07 2014 Boyle s Law P1V1 P2V2 Pressure down Volume up Pressure up Volume down T and n of moles are constant Charles Law V1 T1 V2 T2 Temp up Volume up Temp down Volume down V T constant Temperature must always be in Kelvin K Celsius 273 15 Avogadro s Law V1 n1 V2 n2 moles up volume up moles down volume down V n constant Amonton s Law P1 T1 P2 T1 Temp up pressure up Temp down Pressure down P T constant Convert to K Keep track of variables that change V alpha 1 P V alpha T V alpha n P alpha T PV nT constant R the Gas constant P pressure atm V volume L n moles T temperature K R 0 082057 L x atm mol x k Gas particles don t attract or repel each other Volume of gas particle is negligible compared to the container An ideal gas is a collection of non interacting point particles Non ideal high pressure low temperature IDEAL GAS LAW PV nRT 8 3145 I Mol x k