Combustion Reactions

Reactivity 1.3

Combustion requires

oxygen

Incomplete combustion

CO, C, soot, yellow flame, smoke

Fossil fuels

nonrenewable, unsustainable

Energy density

energy released per unit volume (gasses lower, liquids higher)

Specific energy

energy released per unit mass (gases higher, liquids lower)

Coal

most abundant fossil fuel, sulfur impurities (SOx)

Anthracite

high % carbon

Crude Oil/Petroleum

mixtures of straight-chain & branched-chain alkanes, cycloalkanes, and aromatic compounds

Feedstock for polymers, medications, dyes, and solvents

Absence of O in creatio

Natural Gas

Methane is main compound, Impurities: N2 and S

The cleanest of fossil fuels, minimal amounts of CO

Transported in pipes - initial setup is EXPENSIVE

Coal positives

abundant, longer lifespan, cheap, the ashes can be reused to make asphalt

Coal negatives

Impurities lead to acid rain, contributes to global warming, smog leads to health issues (soot), difficult to transport, mining is dangerous

crude oil positives

easer than coal to extract, pumped up from underground reserves, easy to transport, convenient for cars, higher enthalpy density, S impurities are easier to remove

crude oil negatives

aromatic compounds bad for environment, CO produced by incomplete combustion in cars, photochemical smog produced, N oxides & hydrocarbons released, transport leads to contamination lots of spills, acid rain, global warming

natural gas positives

cleanest of fossil fuels, minimal amounts of CO, easily transported, high specific energy

natural gas negatives

initial setup is EXPENSIVE, contributes to global warming, risk of explosion due to leaks, limited supplies

impact of increasing greenhouse gases: CO2

changes in agriculture, rising sea levels b/c of thermal expansion & melting ice caps, changes in biodistribution (loss of cold water fish habitats)

impact of increasing greenhouse gases: CO2 WHY

blocks UV rays, allow shortwave radiation from the sun to pass through the atmosphere “reradiated”

IR active

dipole changes by stretching & bending

biofuels

renewable and sustainable, inefficient process

gashol

10% ethanol, 90% unleaded gasoline

what harmful products are produced when wood is burned in an enclosed space? 

soot, CO

hydrogen fuel cells

alternative to fossil fuels, doesn’t produce CO2

methanol fuel cells

fracking, stable liquid at normal cond. , high energy density, easy to transport, DMFC, methanol is oxidized in acidic conditions to form CO2