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Chemistry > Fuels > Flashcards

Fuels Flashcards

1
Q

Fuel

A

a substance that can release its stored energy relatively easily to produce useful energy

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2
Q

Renewable*

A

Fuel can be replaced by natural processes within a relatively short period of time
- unlikely to run out in future

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3
Q

Non-renewable*

A

Consumed at a rate greater than it can be produced by natural processes and is likely to run out in the future

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4
Q

Carbon Neutral*

A

Net amount of CO2 released from the use of the fuel is zero
- only theoretical

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5
Q

Non Carbon neutral*

A

The process of releasing energy from the fuel adds to the overall amount of atmospheric CO2.
- fuels contribute to global warming

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6
Q

Fossil fuels

A

Collection of non-renewable, non-carbon neutral fuels that are formed by the decomposition of once living organic matter over millions of years

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7
Q

Coal

A

Decomposition of plant matter over millions of years.
Carbon content increases, water content decreases

peat–> brown coal –> black coal

  • abundant
  • cheap to obtain
  • reliable source of energy
  • non-renewable
  • not carbon neutral
  • acid rain
  • destructive to enviro.
  • contains pollutants (impure) –> damage enviro. when combusted
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8
Q
A
  1. Coal is burnt (chem en –> thermal en)
  2. Heat released from burning of coal used to boil water to form steam (therm –> kinetic en)
  3. Steam used to spin turbine (kin en –> mechanical)
  4. Spinning of turbine to produce elec (mechan. –> elec en)

LOW ENERGY EFFICIENCY (multiple steps)
33% efficiency

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8
Q

Crude oil

A

Mixture of hydrocarbons, mostly alkanes, that is obtained from underground reserves (land or sea).
Crude oil separated into diff components via frac distillation)

  • large reserves still exist
  • non renewable
  • non carbon neutral
  • oil spills –> marine
  • toxic waste produced
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9
Q

Fractional Distillation

A

Mixture of alkanes of varying lengths.
increase chain length –> bp increases (greater net strength of dipole

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10
Q

Natural Gas

A

NOT A BIOFUEl (FOSSIL FUEL)
* mainly composed of methane (CH4)
* obtained from: crude oil, gas reservoirs, coal seam gas

  • virtually no particulate emisions
  • lower co2 emissions
  • non renewable
  • non carbon neutral
  • methane leakages – > major conseq on enviro.
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11
Q

Gas fired power station

A
  1. Gas is burnt (chem en –> kinetic en)
  2. Hot gases used to spin turbine (kin en –> mech en)
  3. Spinning of turbine drives generator to produce electricity (mech en –> elec en)

40% energy efficiency (less energy transformation)

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12
Q

Coal Seam Gas

A

Type of natural gas
Found adsorbed to the surface of coal particles.
Obtained via fracking

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13
Q

Fracking

A
  1. Drill a well
  2. Pump in fracking fluid (water, sand + chemicals) at high pressures to fracture the coal and allow the coal seam gas to be released
  3. Coal seam gas flows to the surface through a pipe where it is collected

Issue: fracking fluid can contaminate local water supplies

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14
Q

Biofuels

A

Fuels that are produced from recently living organic matter.
* renewable and mostly carbon neutral
- Not 100% carbon neutral

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15
Q

Bioethanol

A

Consists of ethanol that has been produced from recently living organic matter, mostly via fermentation of glucose

C6H12O6(aq)–> 2CH3CH2OH(aq)+2CO2(g)

  • Mostly used in E10, fuel made of 90% petrol and 10% bioethanol
16
Q

Bioethanol advantages

A
  • Carbon neutral
  • Renewable
  • Ethanol burns more cleanly than petrol and releases less emissions
  • Wide variety of crops can be used to produce bioethanol
  • more biodegradable than petrol –> less impact on enviro.
  • Can be easily integrated into existing transport fuel system
17
Q

Bioethanol disadvantages

A
  • ethanol = lower energy content than petrol (already partially oxidised)
  • food producing crops may be replaced by crops for bioethanol production
  • increases food scarcity
  • loss of biodiversity if native ecosystems are converted into biofuel crops
  • ethanol is hygroscopic (absorbs water) and this property can lead to fuel lines being damaged
18
Q

Biogas

A

Mixture of methane and carbon dioxide that is formed by the anaerobic decomposition of organic waste by bacteria.

Can be used in gas-fired power stations in the same way as natural gas.

19
Q

Advantages of biogas

A
  • Renewable
  • Carbon neutral
  • reduces waste in landfill
20
Q

Disadvantages of biogas

A
  • infrastructure not available to produce large quantities
  • methane = volatile and explosive gas
  • methane leakages –> harmful enviro conseq. (methane = more potent GHG than CO2)
  • difficult to store gaseous fuels as they take up lots of space
21
Q

Biodiesel

A

Composed of a mixture of esters (type of organic compound) that are produced via transesterification reaction btwn an alcohol and a triglyceride (sourced from veg oils or animal fats)
- often used as a direct substitute for petrodiesel

Triglyceride + 3 alcohol –> 3 esters + glycerol
(requires KOH/NaOH catalyst)

  • If methanol used = methyl esters
  • If ethanol used = ethyl esters
22
Q

Advantages of biodiesel

A
  • renewable
  • carbon neutral
  • low or no sulfur content –> less sulfur dioxide emissions
  • direct substitute for petrodiesel
  • more biodegradable than petrodiesel
23
Q

Disadvantages of biodiesel

A
  • hygroscopic (absorbs water) –> damage fuel lines
  • higher viscosity than petrodiesel –> flows less easily through fuel lines
  • higher cloud point than petrodiesel –> biodiesel solidifies at a higher temp –> more likely to clog fuel lines
  • lower energy content (already partially oxidised)
  • reduce food availability
  • reduces biodiversity
24
Q

Viscosity

A

Resistance to flow (thickness)

25
Q

Cloud point

A

Temp at which crystals start to form in a fuel

26
Q

Transesterification

A

Chemistry (17 decks)

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