Using & Controlling Reactions: Fuels

Question 1

Biofuels

Answer 1

• derived from recently living organisms/their metabolic by-products
• carbon recently extracted from atmospheric carbon dioxide by plants (photosynthesis)… plants used directly as fuel or converted to biogas, alcohol (ethanol), biodiesel

Question 2

Fossil Fuels

Answer 2

• derived from products of photosynthesis millions of years ago (anaerobic breakdown, pressure, high temperatures)
• coal, oil, natural gas

Question 3

Advantages of Ethanol (biofuel)

Answer 3

• renewable

- less harmful pollutants than petrol

Question 4

Disadvantages of Ethanol (biofuel)

Answer 4

• non-renewable fossil fuels used
• slightly decreases fuel economy
• lack of widespread fuel availability

Question 5

Advantages of Biodiesel (biofuel)

Answer 5

• renewable
• biodegradable
• fewer air pollutant emissions
• improved lubrication in engines`

Question 6

Disadvantages of Biodiesel (biofuel)

Answer 6

• NO emissions slightly higher than petrol
• may congeal
• may damage engine
• non-renewable fossil fuels used

Question 7

Advantages of Coal (fossil fuel)

Answer 7

• large reserves
• easily mined
• low cost
• export income

Question 8

Disadvantages of Coal (fossil fuel)

Answer 8

• non-renewable

- causes more pollution than other fossil fuels (carbon dioxide, sulfur oxides, nitrogen oxides, particulates)

Question 9

Advantages of Oil (fossil fuel)

Answer 9

• large reserves
• ease of transport
• raw materials for plastics

Question 10

Disadvantages of Oil (fossil fuel)

Answer 10

• non-renewable

- causes pollution (carbon dioxide, sulfur oxides, nitrogen oxides, unburnt hydrocarbons, particulates)

Question 11

Advantages of Natural Gas (fossil fuel)

Answer 11

• large reserves
• efficient heat source
• moderate cost
• less polluting than other carbon-based fuels

Question 12

Disadvantages of Natural Gas (fossil fuel)

Answer 12

• non-renewable

- causes pollution (carbon dioxide & nitrogen oxides)

Question 13

Complete Combustion of Fuels

Answer 13

= compounds containing carbon and oxygen which undergo complete combustion (in 100% oxygen) will produce only carbon dioxide and water

Question 14

Balancing Complete Combustion Equations

Answer 14

1. write outline - formula, states
   LHS = fuel + oxygen, RHS = carbon dioxide + water
2. balance C
3. balance H
4. balance O
   *because ^H is molar, coefficient of fuel must be 1 (use fractions)

Question 15

Incomplete Combustion of Fuels

Answer 15

= compounds containing carbon and oxygen undergo incomplete combustion in insufficient oxygen (eg. air) will produce carbon dioxide, water, carbon monoxide, soot and some of the reactants

Question 16

Consequences of Incomplete Combustion

Answer 16

• less energy is released than complete combustion
• carbon monoxide: binds with haemoglobin in RBC, lowers oxygen-carrying ability of blood, dizziness/fatigue, loss of consciousness, death
• soot: visual pollution, lowers photosynthetic ability in plants, short-term inhalation = respiratory irritation/coughing, long-term inhalation = bronchitis, asthma, emphysema

Question 17

Energy Density

Answer 17

= quantity of heat energy produced from the combustion of fuel (usually described as molar enthalpy of combustion)
= ^H/M(fuel) kJ/g