Notes

Outline

Thermochemistry Part 2-Energy Sources

Calorimeters Styrofoam (coffee) cup Metallic Bomb Calorimeter

T-6.10 Coffee Cup Calorimeter

T-6.12 Bomb Calorimeter

Determination of Enthalpy Change Using Calorimetric Methods Q rx = -Qcal Q cal = Heat capacity of calorimeter x  DT Example

Hess’s Law The change in enthalpy is independent of the pathway Change in Enthalpy (D H) depends only upon the Enthalpy of reactants and Products

T-6.13 Enthalpy Diagram Illustrating Hess’s Law

Determining Enthalpy Change For A Reaction From Two or More Related Reactions Reversing A Reaction changes the sign on its DH Multiplying A Reaction by a common factor means multiplying the  DH by that same factor If a component is on the opposite side in a given reaction from the requested reaction then reversal is suggested If the coefficients are different for a component then multiplication is suggested Example

Heats of Formation Enthalpy Change In the formation of a compound from its basic elements Heats of Formation for elements will be zero if they are in their native state All elements not in their native state will have a non-zero Heat of Formation Heats of Formations apply to compound formation as well as aqueous ion formation

T-6.2 Table of Heats of Formation

T-6.2B Continuation of Table of Heats of Formation

Hess’s Law of Summation   DH rx = S nDHf (products) - Sn  DHf(reactants)                     where n = coeff in balanced eq Examples

Sources For Energy in US Fossil Coal Petroleum Natural gas Geographical Nuclear Solar

T-6.15  Sources For Energy Consumption in USA

Coal Peat Lignite Bituminous (Soft) Coal Anthracite(Hard) Coal

Disadvantages of Coal Consumption Mining Costs Underground tunneling and timber shoring Safety Hazards Black Lung Mine shaft cave-in Coal Dust explosion Gas explosion Transportation Costs Pollution of Air and Water(Sulfur and Nitrous Oxides,acid rain)

Petroleum Requires Fractional Distillation and Refining Fractionating Distillate Products Gasoline Kerosene Fuel Oils Lubricants Residue Waxes(paraffin)

Refining Methods Cracking-Increases volatility of fuel Thermal Catalytic Additives Ethanol Molybdenum compounds Other Heavy Transition Metals

Advantages Of Using Petroleum Over Coal Much lower mining costs Petroleum a fluid and is transported through pipeline usually under pressure Lower Safety Costs No chance of cave-ins Less chance of explosions Lower Transportaion Costs Transported through pipeline and tankers

Pollution problems With Petroleum Gasoline forms Nitrous Oxides Catalytic Converters solve this Gasoline produces Carbon Monoxide under low Oxygen conditions(idling) Gasoline produces Carbon Dioxide Aggravates the Greenhouse Effect Breakdown of Heavy Metal Additives source of toxicity (Lead, Mb)

Geographical Hydroelectric Wind Tidal Geothermal (hot springs,geysers,etc)

Nuclear Energy Fission-Splitting of Fissionable atoms Fusion-Combining of nuclei under extreme temperatures and pressures

Problems With Fission Radioactive fission products with long half lives High Construction Costs High Safety Costs Uses an exhaustible fuel (.003% of earth’s crust are fissionable Uranium-235 Plutonium-239(created by Uranium Fission)

Fusion Combining of Hydrogen Isotope Nucleii Produces many times more energy than sample size sample of Fissionable fuel Energy of the Sun

Potential of Fusion Products of Fusion is Helium (not radioactive) Much higher energy production per mass of fuel Uses cheap pratically inexhaustible fuel (water)

Solar Power Passive Thermal exchange Active Radiant energy --à electrical energy Requires efficient solar cells

Alternative Fuels Ethanol-Gasoline mixture Hybrid engines Uses electrical when engine idling Electrical Solar Liquified Natural Gas Propane Butane Methane