Chemistry - Greenhouse Effect and Fossil fuels

what is a fossil fuel/ types of fossil fuels

coal, (crude)oil and natural gas

how are fossil fuels formed?

slow and partial decomposition of plant and animal matter in the absence of oxygen

what do living matters contain that are useful? (they get reduced under pressure)

carbon, hydrogen, nitrogen, sulfur and oxygen

what is crude oil

a complex mixture of different hydrocarbons including:

• mainly saturated alkanes

• straight-chained and branch chained hydrocarbons

• cycloalkanes

why is sulfur dangerous?/why do we need to remove sulfur from crude oil?

1. it releases sulfur dioxide when combusted that can lead to acid rain

2. it can ‘clog up’ further reactions

how to remove sulfur?

desulfurisation

what are some disadvantages of coal

1. it contains a lot of extra pollutants

2. produces CO2 and SO2 particulates(electrostatic preceptors can remove these)

3. it is difficult to transport - solid

4. waste can lead to visual and chemical pollution

5. mining is dangerous

what are some advantages of coal?

1. cheap and plentiful

2. can be converted to synthetic liquid fuels and gases

3. ash produced can be used in making roads

what are some advantages of crude oil?

1. easily transported in pipelines or tankers

2. convenient fuel for use in cars as volatile and burns easily

3. sulfur impurities are easily removable

what are some disadvantages of crude oil?

1. limited lifespan and uneven world distribution

2. contributes to acid rain and global warming

3. transport can lead to pollution

4. carbon monoxide is a local pollutant produced by incomplete combustion of gasoline in internal combustion engines

5. photochemical smog produced as secondary pollutant due to reactions of primary pollutants(nitrogen oxides and hydrocarbons) released from internal combustion engines

natural gas

1. produces fewer pollutants per unit energy

2. easily transported in pipelines and pressurised containers

3. does not contribute to acid rain

4. higher specific energy

what are some disadvantages of natural gas?

1. limited supply

2. contributes to global warming

3. risk of explosion due to leaks

whar are renewable energy sources?

naturally replenished on a human time scale - at a rate faster than it is used

what are non-renewable energy sources?

finite

how to choose the best energy source?

1. releases energy at a reasonable rate

2. produces minimal pollution

3. efficient conversion of energy

4. cheap, plentiful and readily available

what is a fuel?

a substance that can release energy by changing its chemical or nuclear structure

standard enthalpy change of combustion

enthalpy change when one mole of fuel is combusted completely in excess oxygen

what are the advantages of biofuels?

1. renewable

2. not a significant impact to pollution

3. safer to produce than coal

4. waste can be turned into biogas

what are the disadvantages of biofuels?

1. land could be used for other things

2. fertilisers may run off and pollute water

3. removes nutrients from soil and causes erosion

4. only occurs at a small scale at present time

why is change H = mcT/mol not good to use for fuel?

need to think about storage and transport - use mass instead of moles