Chapter 2 - Carbon-Based Fuels

Question 1

Activation Energy

Answer 1

The energy required to break the bonds of the reactants in a chemical reaction.

Question 2

Biodiesel

Answer 2

A mixture of organic compounds (esters), formed from vegetable oils through a process called transesterification.

Question 3

Bioethanol

Answer 3

Ethanol - C₂H₅OH - formed from the fermentation of glucose obtained from plants (mainly sugar cane, wheat & forest waste).

Question 4

Biogas

Answer 4

A mixture of carbon dioxide and methane formed during the anaerobic (“without oxygen”) decomposition of organic material (e.g. sewage).

Question 5

Biomass

Answer 5

Organic matter (e.g. plant & animal waste) that is used as a fuel (e.g. biogas).

Question 6

Cellular Respiration

Answer 6

The process through which cells in the body extract energy from glucose according to the equation:
C₆H₁₂O₆(aq) + 6O₂(g) → 6CO₂(g) +6H₂O(l) ; ∆H = -2803 kJ

Question 7

Chemical Energy

Answer 7

The energy stored in the bonds of chemical compounds, made up of its kinetic energy (movement) and potential energy (e.g. gravitational, magnetic, etc).

Question 8

Combustion

Answer 8

The burning of a fuel in oxygen to form carbon dioxide and water.
Fuel + Oxygen → Carbon Dioxide + Water

Question 9

Complete Combustion

Answer 9

Combustion in an excess of oxygen, forming carbon dioxide.

Question 10

Distillation

Answer 10

The process of purifying an aqueous solution by boiling and cooling a mixture.

Question 11

Endothermic

Answer 11

A reaction that absorbs energy (e.g. dissolving), resulting in a decreased temperature. H(products) > H(reactants). i.e. ∆H > 0.

Question 12

Energy Profile Diagram

Answer 12

A graph illustrating the energy of a reaction as time progresses. Energy is absorbed to break bonds and released to make bonds.

Question 13

Enthalpy (H)

Answer 13

The heat content of a substance. Note: can’t be directly measured, only the change in enthalpy (∆H).

Question 14

Enthalpy of Combustion (∆H_c)

Answer 14

(Also ‘heat of combustion’) The heat energy released when one mole of a substance burns completely in oxygen.

Question 15

Exothermic

Answer 15

A reaction that releases energy (e.g. combustion), resulting in an increased temperature. H(products) < H(reactants). i.e. ∆H < 0.

Question 16

Fermentation

Answer 16

The process through which a substance is broken down by a microorganism or enzyme. Used to create bioethanol.

Question 17

Fossil Fuel

Answer 17

A non-renewable fuel formed from dead biological material (e.g. coal, oil, natural gas).

Question 18

Fuel

Answer 18

A substance with stored chemical energy which can be easily released for heat or power.

Question 19

Hydrocarbon

Answer 19

A compound containing hydrogen and carbon, such as methane (CH₄).

Question 20

Incomplete Combustion

Answer 20

Combustion in an insufficient supply of oxygen, forming carbon monoxide (CO) or carbon soot (C).

Question 21

Joule

Answer 21

The unit for energy.

Question 22

Natural Gas

Answer 22

A fossil fuel consisting mainly of methane, with small amounts of ethane and propane.

Question 23

Photosynthesis

Answer 23

The process through which plants convert the sun’s energy into chemical potential energy according to the formula:
CO₂(g) +6H₂O(l) → C₆H₁₂O₆(aq) + 6O₂(g) ; ∆H = +2803 kJ

Question 24

Thermochemical Equation

Answer 24

A balanced chemical equation which displays the enthalpy value of the reaction. e.g. CH₄(g) + 2O₂(g) → CO₂(g) +2H₂O(l) ; ∆H = -890 kJ

Question 25

System

Answer 25

The chemical reaction taking place (e.g. combustion).

Question 26

Surrondings

Answer 26

The area around a chemical reaction (e.g. air, water, etc).

Question 27

Fermentation of Glucose Equation

Answer 27

C₆H₁₂O₆(aq) → 2C₂H₅OH(aq) + 2CO₂(g)
Note: then needs to be distilled for combustion

Question 28

Energy Content (kJ/g)

Answer 28

The amount of energy in a mixture (e.g. foods). Cannot have enthalpy calculated since they do not have a molar mass.