Fuels

Question 1

What is petrol comprised of?

Answer 1

• A mix of alkane hydrocarbons

Question 2

What is natural gas comprised of?

Answer 2

• Methane, followed by ethane, propane…

Question 3

Where is natural gas found?

Answer 3

• Found in coal and petroleum deposits

Question 4

How is bioethanol produced?

Answer 4

• Via anaerobic fermentation
• Needs to be separated from fermented solution using distillation

Question 5

Why does bioethanol need to be separated from its fermented solution?

Answer 5

• If aqueous, water needs to be separated from the bioethanol
• Removing water increases energy content.

Question 6

How is biogas made?

Answer 6

• Released in breakdown of organic matter by anaerobic bacteria

Question 7

What is biodiesel comprised of?

Answer 7

• Mixture of esters

Question 8

How is biodiesel produced?

Answer 8

• Produced between fats + oils and alcohol via transesterification

Question 9

Advantages of coal

Answer 9

• Large reserves
• Easy transport
• High energy content

Question 10

Disadvantages of Coal

Answer 10

• High emissions
• Non-Renewable

Question 11

Advantages of Natural Gas

Answer 11

• More efficient than coal
• High energy content

Question 12

Disadvantages of Natural Gas

Answer 12

• Limited reserves
• Polluting (less than coal and petrol)

Question 13

Advantages of biogas

Answer 13

• Made from waste
• Low cost
• CO2 absorbed (photosynthesis)

Question 14

Disadvantages of Biogas

Answer 14

• Low energy content
• Supply of raw materials is limited

Question 15

Advantages of Petrol

Answer 15

• High energy content
• Easy transport

Question 16

Disadvantages of Petrol

Answer 16

• Polluting (Less than coal)
• Limited reserves

Question 17

Advantages of Bioethanol

Answer 17

• Can be made from waste
• CO2 absorbed (photosynthesis)
• Burns smoothly

Question 18

Disadvantages of Bioethanol

Answer 18

• Limited supply
• Lower energy content than petrol
• May require farmland which would otherwise be used for food

Question 19

Is photosynthesis an endo or exothermic reaction

Answer 19

• Endothermic

Question 20

Is cellular respiration an endo or exothermic reaction?

Answer 20

• Exothermic

Question 21

Is direct combustion efficient in comparison to direct conversion of energy?
Why?

Answer 21

• Direct combustion, i.e. car or power station, is less efficient
• There are more steps in this process where energy can be lost
• More energy is lost due to transformations required
  (think of all the different mechanisms the energy needs to pass through… each loses energy)

Question 22

Is the direct conversion of energy efficient in comparison to direct combustion?
Why?

Answer 22

• Chemical to electrical energy conversion, i.e. fuel cells (do not require combustion)
  are more efficient
• There are less steps in this process, meaning less energy is lost due to less transformations required.

Question 23

Why does 2-methylpropan-1-ol have a lower energy content value than octane?

Answer 23

• 2-methylpropan-1-ol is partially oxidised

Question 24

How does energy differ in incomplete combustion, in comparison to complete combustion?

Answer 24

• The energy of the products would be higher in incomplete combustion in comparison to complete, but still below reactants
• This is due to incomplete oxidisation of reactants

Question 25

In combustion, partially oxidised compounds release…

Answer 25

… less energy than compounds not partially oxidised