Fuels

Question 1

What is a fuel?

Answer 1

a substance that burns in air or oxygen to release a usable amount of energy

Question 2

Which of the following are examples of fossil fuels?
a) Methane
b) Octane
c) Biodiesel
d) Bioethanol
e) CSG (coal seam gas)
f) Liquid petroleum gas (LPG)
g) Natural gas
h) Biogas
i) Diesel/petrodiesel

Answer 2

a) Methane
b) Octane
e) CSG (coal seam gas)
f) Liquid petroleum gas (LPG)
g) Natural gas
i) Diesel/petrodiesel

Natural gas is mainly methane

Question 3

Describe the greenhouse effect

Answer 3

The process of the warming of the Earths lower atmosphere due to the increased quantities of gases of ‘greenhouse gases’ such as carbon dioxide, water vapour and methane in the air

Question 4

a) What is a biofuel.
b) Name three biofuels

Answer 4

a) a fuel sourced from biomass

b) biogas, bioethanol, biodiesel

Question 5

Define fossil fuel.

Answer 5

a natural fuel formed over millions of years in the earth from plant or animal remains

Question 6

What is petrodiesel?

Answer 6

A liquid hydrocarbon fuel obtained from crude oil

Question 7

Which type of fuel has a lower energy content; biofuels or their fossil fuel equivalent, i.e. biogas or CH4 sourced from fossil fuel?

Answer 7

biofuels have a lower energy content compared to their fossil fuel equivalents, i.e. CH4 sourced from fossil fuel with have a higher energy contact than biogas

Biogas = lower proportion of methane 30-60% compared to natural gas ~90%

Question 8

State if fuels generally have a high or low boiling point, flashpoint, flammability

Answer 8

Fuels generally have low boiling point, low flashpoint (the temperature at which a particular organic compound gives off sufficient vapour to ignite in air) and high flammability

Question 9

State some storage considerations for a fuel

Answer 9

store away from naked flames (because fuels are flammable)
store in well ventilate areas (to avoid suffocation / asphyxiation)

Question 10

State some safety considerations for dealing with fuels with a low boiling point

Answer 10

use / store away from naked flame (as the fuels will be flammable)
work in well ventilated areas (as vapours can be harmful)
avoid contact to the skin and eyes by wearing safety glasses, labcoat and gloves if required

Question 11

State the intermolecular bonding that can occur between hydrocarbons

Answer 11

dispersion forces

Question 12

Explain why the boiling point of pentane is higher than he boiling point of ethane

Answer 12

Comment of the structure of the molecules, then identify the intermolecular bonding before linking to the question.

Because pentane (C5H12) is a longer chain hydrocarbon compared to ethane (C2H4),
Then pentane has a larger number of dispersion forces acting between the molecules
Therefore a greater level of energy is required to disrupt the dispersion forces between pentane, hence pentane has a higher boiling point.

Question 13

Explain why the boiling point of propane is lower than the boiling point of ethanol

Answer 13

Comment of the structure of the molecules, then identify the intermolecular bonding before linking to the question.

Because ethanol contains a hydroxyl group whereas propane is a straight chain hydrocarbon
Then hydrogen bonds form between the hydroxyl (-OH) groups of ethanol molecules whereas only dispersion forces exist between propane molecules
Therefore the stronger intermolecular bonds between ethanol molecules require a greater kinetic energy to overcome causing ethanol to have a higher boiling point

Question 14

Define the term flashpoint

Answer 14

the temperature at which a particular organic compound gives off sufficient vapour to ignite in the air

Question 15

Explain why the flashpoint of propan-1-ol is higher than the flashpoint of propan-2-ol

Answer 15

Comment on the structure of the molecules, then identify the intermolecular bonding before linking to the question

Because propan-2-ol has branched chain molecules whereas propan-1-ol has straight chin molecules
Then the propan-1-ol molecules are able to fit closer together allowing the dispersion forces between propan-1-ol molecules to be stronger than the dispersion forces between propan-2-ol molecules as the forces are acting over a shorter distance
Therefore greater energy is required to disrupt the bonds between propan-1-ol molecules causing it to be less easily vapourised.

Question 16

Define renewable resource

Answer 16

one that can be replenished at a rate as quickly or faster than the rate they are being consumed / used

Question 17

Define non-renewable resource

Answer 17

One that is NOT able to be replenished at a rate greater than or equal to the rate it is being consumed / used

Question 18

Identify three examples of renewable fuels

Answer 18

Biogas,
Bioethanol,
Biodiesel

Question 19

Identify three examples of non-renewable fuels

Answer 19

Natural gas,
Coal,
Coal-seam gas,
Diesel / Petrodiesel (from crude oil)
Ethanol, if produced from hydration of ethane that is sourced from crude oil.

Question 20

Explain why biofuels produced from plants are considered to be almost carbon neutral (have approximately zero net impact on atmospheric carbon dioxide).

Answer 20

Because plants undergo photosynthesis whilst they grow, they absorb carbon dioxide from the atmosphere.
Then when the plant is converted into a biofuel and udergoes combustion, the carbon dioxide absorbed by the plant is released back into the atmosphere.
Therefore there is no NET release of carbon dioxide in to the atmosphere

Question 21

What are some advantages of using coal as a fuel?

Answer 21

Large reserves
Relatively high energy content

Question 22

What are some disadvantages of using coal as a fuel?

Answer 22

Non-renewable
Increases atmospheric carbon dioxide levels which contribute to global warming
Less easily transported than liquid or gaseous fuel (as cannot be transported in pipes)
Releases sulfur based pollution and other particulates into the atmosphere

Question 23

What are some advantages of using natural gas as a fuel?

Answer 23

Relatively high energy content
More efficient than coal for electricity production
Easy to transport through pipes

Natural gas is more efficient as a fuel than coal as there are less step

Question 24

What are some disadvantages of using natural gas as a fuel?

Answer 24

Non-renewable
Limited reserves
Releases greenhouse gases such as CO2 (but less compared to coal and petrol)

Question 25

What are some advantages of using biogas as a fuel?

Answer 25

Renewable Almost net zero release of atmospheric carbon dioxide because carbon dioxide is absorbed by the plants during photosynthesis Produced from waste Reduces waste disposal Low running costs zero sulfur emissions Burns / combusts more completely

Question 26

What are some disadvantages of using biogas as a fuel?

Answer 26

Less energy dense compared to fossil fuel alternatives Supply of waste raw materials is limited

Question 27

What are some advantages of using petrol / petrodiesel as a fuel?

Answer 27

High energy content Ease of transport

Question 28

What are some disadvantages of using petrol / petrodiesel as a fuel

Answer 28

Non-renewable Increases atmospheric carbon dioxide levels Polluting, but less than coal

Question 29

What are some advantages of using bioethanol as a fuel?

Answer 29

Renewable Almost net zero release of atmospheric carbon dioxide because carbon dioxide is absorbed by the plants during photosynthesis can be made from waste Burns smoothly Fewer particulates produced compared to petrol

Question 30

What are some disadvantages of using bioethanol as a fuel?

Answer 30

Limited supply of raw materials from which to produce it Lower energy content than petrol May require use of farmland otherwise used for food production

Question 31

How is biodiesel formed?

Answer 31

Esterification of fats and oils in organic matter (animal products and oils originating from crops). Biodiesel is formed form a reaction between a fatty acid with an alkanol

Question 32

What is the main functional group present in biodiesel

Answer 32

ester

Question 33

What is another name commonly used to identify biodiesel

Answer 33

methyl ester

Question 34

what are some sources of methane gas?

Answer 34

Biogas, natural gas and coal seam gas

Question 35

What is the photosynthesis formula equation?

Answer 35

6CO2 + 6H2O -> C6H12O6 + 6O2

Question 36

What is the word equation for photosynthesis?

Answer 36

carbon dioxide + water -> glucose + oxygen

Question 37

What is biogas?

Answer 37

A mixture of gases (mainly methane) produced by the breakdown of organic waste by anerobic bacteria. These bacteria decompose the complex molecules in carbohydrates and proteins into molecules such as carbon dioxide and methane.

Question 38

How is biogas produced?

Answer 38

Biogas is produced from the anaerobic breakdown of biomass / organic matter by bacteria. Examples of biomass include algae, crops, wood, compostable garbage.

Question 39

How is bioethanol produced?

Answer 39

by the fermentation of glucose in organic matter by a microorganism called yeast. Example of organic matter include crops such as wheat, corn and sugarcane.

Question 40

Write the word equation and balanced formula equation for the fermentation of ethanol

Answer 40

Glucose -----(bacteria)----> Ethanol + Carbon dioxide C6H12O6 (aq) ------(bacteria)---->2CH3CH2OH(l) + 2CO2(g) (note the glucose in the fermentation equation is aq. aqueous)

Question 41

What is a triglyceride composed of?

Answer 41

3 fatty acid chains and 1 glycerol molecule, joined via ester links

Question 42

What is produced when a triglyceride reacts with an alkanol such as methanol in the presence of a catalyst?

Answer 42

3 biodiesel molecules (methyl esters) and 1 glycerol molecule

Question 43

A triglyceride will react with an alkanol to form biodiesel and glycerol. What is the name of this type of reaction?

Answer 43

transesterification

Question 44

What is produced when a fatty acid reacts with an alkanol such as methanol?

Answer 44

1 biodiesel molecule (methyl ester) + 1 water molecule

Question 45

Compare the properties of biodiesel versus petrodiesel

Answer 45

- biodiesel has higher viscosity than petrodiesel - biodiesel has higher freezing point than petrodiesel - biodiesel has higher viscosity particularly at cold temperatures - biodiesel is more hygroscopic (absorbs more water) than petrodiesel - biodiesel has higher melting point than petrodiesel - biodiesel is less energy dense than petrodiesel - biodiesel forms a gel / crystalises at a higher temperature (resulting in increased viscosity and poor flow at lower temps) - biodiesel is more likely to oxidise causing a gum-like substance to form in the fuel.

Question 46

compare the production of biodiesel versus petrodiesel

Answer 46

Biodiesel is produced from biomass / organic matter which is a renewable energy source where as petrodiesel is produced from fossil fuels which is non-renewable. Biodiesel requires land and water to produce. This land / water could otherwise be used for food production. Petrodiesel requires drilling of crude oil. Oil fields / refinaries are prone to oil spills and produce emissions that have a negative affect on the environment.

Question 47

Compare the environmental affect of biodiesel versus petrodiesel

Answer 47

Biodiesel produces a lower (almost net zero) net emission of carbon dioxide due to partial offset from the absorption of CO2 through photosynthesis whist growing. whereas Petrodiesel has a greater net emission of carbon dioxide into the atmosphere Biodiesel produces fewer particulates and fewer pollutants compared to petrodiesel.

Question 48

Explain how the presence of the polar ester bond in biodiesel affects its properties compared to petrodiesel and how this affects the use of biodiesel

Answer 48

The presence of the ester bond causes biodiesel to be more hygroscopic (absorb water) as the ester bond forms hydrogen bonds with water. The presence of water decreases the heat of combustion of the fuel, increases the likelihood of corrosion of fuel system and increases smoke produced when the fuel burns. The ester bond results in biodiesel having higher viscosity than petrodiesel as dipole-dipole bonds form between the molecules compared to dispersion bonds between petrodiesel molecules. The ester bond results in biodiesel being more likely to oxidise causing a gum like substance to form in the fuel. This can block fuel lines and filters. The oxidation results in the fuel becoming more acidic which can lead to corrosion

Question 49

True or False: Fossil fuels are derived from ancient organic materials.

Answer 49

True

Question 50

What is an exothermic reaction?

Answer 50

A reaction where more energy is released forming new bonds in the products than is used to break bonds in the reactants causing energy to be released to the surroundings as heat energy and the observed temperature increases. | Negative enthalphy change ## Footnote 02

Question 51

What is an endothermic reaction?

Answer 51

A reaction where more energy is used to break bonds than is released forming new bonds in the products causing energy to be abosorbed from the surroundings. The observed temperature therefore decreases | positive enthalpy change

Question 52

True or False: In exothermic reactions, the products have higher energy than the reactants.

Answer 52

False

Question 53

Fill in the blank: In an endothermic reaction, the enthalpy change (ΔH) is __________.

Answer 53

positive

Question 54

Fill in the blank: In an exothermic reaction, the enthalpy change (ΔH) is __________.

Answer 54

negative

Question 55

What occurs during bond breaking in a chemical reaction?

Answer 55

Energy is absorbed to overcome the forces holding the atoms together.

Question 56

What occurs during bond making in a chemical reaction?

Answer 56

Energy is released as new bonds form between atoms.

Question 57

Which type of reaction typically has a decrease in temperature in the surroundings?

Answer 57

Endothermic reaction

Question 58

Which type of reaction typically has an increase in temperature in the surroundings?

Answer 58

Exothermic reaction

Question 59

True or False: All exothermic reactions are spontaneous.

Answer 59

False

Question 60

What is the relationship between bond strength and enthalpy changes in exothermic reactions?

Answer 60

Exothermic reactions form stronger bonds in products than those in reactants. The bonds between the atoms in the products of an exothermic reaction have a stronger chemical bond, which store less potential energy (are at a lower energy state) compared to weaker bonds, requiring more energy to break. Forming stronger bonds releases more energy, placing atoms in a more stable, lower-energy configuration.

Question 61

What is a key difference in energy changes between exothermic and endothermic reactions?

Answer 61

Exothermic reactions release energy, while endothermic reactions absorb energy.

Question 62

Multiple Choice: Which of the following is an example of an exothermic process? A) Photosynthesis B) Combustion C) Melting ice

Answer 62

B) Combustion

Question 63

Multiple Choice: Which of the following processes are endothermic? A) Dissolving salt in water B) Burning wood C) Respiration D) Photosynthesis E) converting ice to liquid water, F) converting water vapour to liquid water

Answer 63

A) Dissolving salt in water D) photosynthesis E) converting ice to liquid water

Question 64

What is the unit commonly used to measure enthalpy changes?

Answer 64

Kilojoules per mole (kJ/mol)

Question 65

List the types of biofuels.

Answer 65

* Biogas * Bioethanol * Biodiesel ## Footnote Biofuels are renewable resources produced from biomass

Question 66

What is renewability?

Answer 66

The ability of a resource to be replaced by natural processes within a relatively short period of time. ## Footnote This concept is critical in distinguishing between fossil fuels and biofuels.

Question 67

What are the fuel sources for the body measured in kJ g-1?

Answer 67

* Carbohydrates * Proteins * Lipids (fats and oils) ## Footnote These macronutrients provide energy for bodily functions.

Question 68

What is photosynthesis?

Answer 68

The process that converts light energy into chemical energy by reacting together water and carbon dioxide to produce glucose and oxygen. Chlrorphyll and light energy are required for the reaction to occure ## Footnote The equation is: 6CO2(g) + 6H2O(l) → C6H12O6(aq) + 6O2(g).

Question 69

What is the balanced equation for aerobic cellular respiration?

Answer 69

C6H12O6(aq) + 6O2(g) → 6CO2(g) + 6H2O(l) ## Footnote This process involves the oxidation of glucose as a primary energy source.

Question 70

What is the process for the production of bioethanol? Include molecular equations.

Answer 70

Fermentation of glucose followed by distillation. Equation is C6H12O6(aq) → 2C2H5OH(aq) + 2CO2(g) for fermentation. Distillation is 2C2H5OH(aq) to 2C2H5OH(l) as water is removed

Question 71

What units are used to measure enthalpy changes?

Answer 71

Measured in kJ, molar enthalpy changes in kJ mol-1, and enthalpy changes for mixtures in kJ g-1. ## Footnote These measurements are crucial for understanding energy changes in chemical reactions.

Question 72

What are combustion reactions?

Answer 72

Exothermic reactions involving the reaction of fuels with oxygen, resulting in the release of energy. ## Footnote Includes complete and incomplete combustion.

Question 73

What is the difference between complete and incomplete combustion?

Answer 73

Complete combustion produces carbon dioxide and water, while incomplete combustion produces carbon monoxide and/or soot + water ## Footnote Balanced thermochemical equations are used to represent both types.

Question 74

What is meant by a sustainable fuel?

Answer 74

A sustainable fuel has two factors. It is renewable, meaning it can be produced at a rate greater than the rate it is used AND it does not affect future generations.