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Question 1

define fuel

Answer 1

a fuel is a substance with stored energy that can be released relatively easily for use as heat or power.

Question 2

define a renewable energy source

Answer 2

a source of energy that can be used indefinitely as the source can be replaced using natural processes in a short amount of time.

Question 3

examples of renewable energy sources

Answer 3

biofuels (bioethanol, biogas, biodiesal), solar power, hydroelectricity, etc

Question 4

define a nonrenewable energy source

Answer 4

a source of energy that cannot be replenished by natural processes faster than it is consumed and is in limited supply

Question 5

examples of nonrenewable energy sources

Answer 5

fossil fuels (crude oil, coal, natural gas)

Question 6

define photosynthesis

Answer 6

photosynthesis is a process that converts light energy to chemical energy as a source of glucose and oxygen for respiration in living things.

Question 7

what is the photosynthesis equation

Answer 7

6CO2(g)+6H20(l) -(sunlight)> C6H12O6(aq)+6O2(g)

Question 8

what is the equation of cellular respiration

Answer 8

6O2(g)+C6H12O6(aq) -> 6CO2(g)+6H2O(l)

Question 9

compare exothermic and endothermic reactions

Answer 9

endothermic reactions absorb energy (in the form of heat) from surroundings, while exothermic reactions release heat energy to surroundings.

Question 10

compare the chemical energy of the products and reactions in endothermic and exothermic reactions

Answer 10

endothermic reactions: the reactants have less chemical energy than the products

exothermic reactions: the reactants have more chemical energy than the products

Question 11

compare the energy required to break bonds in the reactants and the energy released when products are formed in exothermic and endothermic reactions

Answer 11

exothermic reactions: the energy released when the bonds in the products form is greater than that of the energy required to break bonds in the reactants.

endothermic reactions: the energy released when the bonds in the products form is less than that of the energy required to break bonds.

Question 12

compare enthalpy change in exothermic and endothermic reactions

Answer 12

endothermic reactions: enthalpy change is positive

exothermic reactions: enthalpy change is negative

Question 13

how do you determine the limiting reactant/reagent

Answer 13

1. calculate the moles of both reactants
2. divide the moles of each reactant by the coefficient (requires balanced equation to do this)
3. whichever reactant has the lower number is the limiting reagent

Question 14

how is bioethanol produced

Answer 14

• produced from glucose and other sugars in a process called fermentation
• enzymes & microorganisms catalyse (facilitate) the reaction at 35 degrees celsius (any higher, and the enzymes & microorganisms will die)

Question 15

reaction of fermentation of bioethanol

Answer 15

C6H12O6 (aq) -(yeast)> 2CH3CH2OH (aq) + 2CO2 (g)

Question 16

what are the three main bioethanol feedstocks in Australia

Answer 16

• sugar cane
• wheat
• forest waste

Question 17

what is distillation

Answer 17

a process that uses the different boiling points of liquids to separate them

Question 18

is bioethanol carbon-neutral

Answer 18

• not completely, but more than ethanol that is obtained from crude oil
• a lot of energy is required to distil the ethanol solution, making its production not a carbon-neutral process

Question 19

how is coal used to generate energy

Answer 19

• combustion of coal produces energy
  C (s) + O2 (g) -> CO2 (g)
• thermal energy produced from combustion heats a boiler, boiler produces steam, steam turns a turbine which generates electrical energy

Question 20

how is petrol produced

Answer 20

• produced from crude oil
• use of distillation to produce petrol (octanes and other alkanes)

Question 21

how is natural gas produced

Answer 21

• natural gas is found in deposits in the Earth’s crust
• naturally occurring in the Earth’s crust, but in limited quantities

Question 22

what is the difference between complete and incomplete combustion

Answer 22

complete combustion:
- occurs when oxygen is plentiful
- only produces co2 and water

incomplete combustion:
- occurs when oxygen supply is limited
- when less oxygen is available, not all the carbon available can be converted into co2
- carbon monoxide (co) (and sometimes carbon) is produced instead of co2

Question 23

what is heat of combustion of a fuel

Answer 23

the heat energy released when a specified amount of a substance burns completely in oxygen.
it is always a positive value.

Question 24

what is enthalpy of combustion

Answer 24

found in thermochem eqns. always a neg value to reflect the nature of a combustion reaction (heat is released)

Question 25

% eff formula

Answer 25

% efficiency = (q into water/q into fuel) * 100

Question 26

advantages of bioethanol

Answer 26

- able to be replaced in short amounts of time with natural processes (renewable) - more carbon neutral than fossil fuels as co2 is absorbed when plants photosynthesise - can be produced from some waste material (such as forest waste)

Question 27

disadvantages of bioethanol

Answer 27

- bioethanol can't be used on its own as a fuel, so it needs to be blended with fossil fuels - some food stocks are used to produce bioethanol (wheat, sugarcane), this could cause food shortages - lower energy content than regular petrol due to ethanol already being partially oxidised

Question 28

what is biogas

Answer 28

- gas produced via anaerobic digestion of waste from bacteria

Question 29

what is the composition of biogas

Answer 29

mostly methane, then carbon dioxide, then everything else