Managing Resources Flashcards
How are fossil fuels formed and why are they considered non-renewable? Include examples
- Formed over geological time scales by anaerobic decomposition of dead organisms under metamorphic conditions
- They are considered non-renewable because the reserves are depleted more quickly than they can form.
- Examples include coal, petroleum, and natural gas.
What is renewable energy? Include examples
- Is energy formed over geological time scales, that replenishes sources much more quickly than fossil fuel sources.
- Examples include, sunlight, wind, biodiesel, geothermal, hydroelectric.
Where does energy come from?
- The combustion of fuels.
- Energy is released because energy is stored in bonds
- exothermic reaction.
What are fossil fuels used for?
Energy production an feedstock for live animals.
Describe what biofuels are, how they are made, examples, and are they renewable or not?
- Biofuels are produced by present day biological processes.
- Examples include, bioethanol, biodiesel and biogas.
- They are derived from biomass (organic matter from plants) and waste matter from plants.
- They are a renewable source because it is considered better than fossil fuels including oil and coal. It is a low production time scale because it takes minutes from the production of animal waste and years for the production of plants and algae.
What is bioethanol a alternative fuel source for?
- petrol.
- can be blended with E10 (existing petrol) or used pure as a fuel source.
How is bioethanol produced?
1 of 2 ways is the fermentation of glucose under anaerobic respiration to produce ethanol.
glucose -> 2ethanol + 2(carbon dioxide)
C6H12O6(aq) -> 2C2H5OH(l) + 2CO2 (g)
(exothermic reaction).
- The second way that it can be produced is through the hydrolysis of polysaccharides (polymer sugars) using enzymes.
Formula for reaction equation is:
(C6H10O5)n(aq) +nH2O(l) -> n(C6H12O6) (aq).
How do you purify bioethanol?
- To purify fractional distillation can be used - separates based off boiling point. Alcohol evaporates first - this removes any outstanding methanol that could have been produced by the enzymes during hydrolysis.
What is biodiesel and what is it derived from?
- An alternative to petroleum diesel and can easily be incorporated into diesel blends.
- Triglycerides, sources from animal fats, oils, plants and algae.
What is complete combustion?
- Occurs when sufficient oxygen is present to convert all carbon atoms to carbon dioxide, where carbon is converted to its highest oxidation state of +4.
- Products are water and carbon dioxide.
What is incomplete combustion?
- Two types, where carbon monoxide is formed and soot is formed through further incomplete combustions.
- Happens when there is NOT sufficient enough oxygen to convert all carbon atoms to its highest oxidation state and from CO2.
Why does incomplete combustion occur more readily as MW increases?
- common during fuel combustion and combustion engines.
- larger hydrocarbon molecules need more oxygen to facilitate the reaction but the availability of oxygen is limited, reducing the amount of carbon dioxide that can be formed.
- Larger molecules also have stronger dispersion forces, which makes them less volatile fuel sources (more energy required to break interactions).
Effects of Carbon monoxide?
- binds to haemoglobin, which transports oxygen within the blood stream.
- carbon monoxide binds more strongly than oxygen therefore less oxygen can go around the body, decreasing oxygen supply to the human and therefore can cause fatigue, dizziness, loss of consciousness and even death.
Effects of carbon soot?
- soot is an aggregate of carbon nanoparticles.
- it can limit visibility in urban areas, blackening surfaces and causing visual pollution.
- covers plant leaves reducing photosynthesis.
- Can be inhaled and cause respiratory illnesses.
What happens as you increase chain length and combustion?
- More oxygen is needed for complete combustion to occur, but less can be facilitated, therefore it undergoes incomplete combustion more readily.
- As chain length increases the molecules becomes more unsaturated as well.
Molecules with higher MW has stronger intermolecular dispersion forces, increasing boiling point and limiting their ability to mix with gaseous molecules.
What is a thermochemical equation?
- Complete or incomplete combustion with an enthalpy value.
- Displays the amount of energy released (in this case) from the exothermic reaction.
- represents molar enthalpy for one mole of fuel.
What to include:
- Fuel + oxidant -> water + carbon dioxide/carbon monoxide/soot.
- Fully balanced - balance oxygen with fractions
- states of matter
- enthalpy sign and value
What does an energy profile diagram display?
- An energy profile diagram represents potential energy vs reaction pathway pathway or progress.
- This shows how the potential energy of a reaction changes over time.
What is enthalpy change in a reaction?
- the difference between the potential energy of the reactants and the products.
- Endothermic reaction: positive sign - products have a a higher difference in potential energy than reactants. Heat is absorbed.
Exothermic reaction: negative sign - reactants have higher potential energy than products. Heat is released.
How do you measure enthalpy?
- Calorimetry: You measure the change of heat during a chemical reaction (combustion).
- This is done through a calorimeter: An insulated vessel that measures energy changes with minimal heat loss to the surroundings.
What is bomb calorimetry and how is it better?
- It is an insulated reaction vessel that is pressurized with oxygen gas to ensue complete combustion occurs.
- It is used to measure enthalpy for combustions of solids and liquids.
What are some errors in calorimetry?
- Incomplete combustion occurring of the fuels witch could result in less energy released.
- Heat being lost - the heat could be absorbed by the metal or the air as opposed to the water.
- The release of heat from combustion is not instantaneous, meaning some heat may be absorbed by the water, but this could be further lost by the air.
- Depending on the fuel, mass could change overtime due to evaporation at these temperatures.
Describe the enthalpy of combustion.
- The combustion of fuels results in a net release of energy meaning it is an exothermic reaction.
- This energy is released when covalent bonds are FORMED between carbon, oxygen and hydrogen in the two complete combustion products.
Formula’s for enthalpy of combustion.
- The quantity of heat released in combustion (enthalpy) is given by the following equation:
Q = m x c x ^T (joules)
Where Q is the quantity of heat released.
m is the mass of water
c is 4.18
^T is the temperature difference
Molar enthalpy of combustion represents the quantity of heat released per mole of fuel that undergoes combustion.
^H = m x c x ^T/1000 x n (KJ/mol)
n is moles of fuel that have undergone combustion.
How can you compare fuels?
- Their energy output and nature of the product of their combustion.
When comparing fuels:
- calculate the quantities of heat evolved per mole, per gram, and per litre (for liquids) for the COMPLETE combustion of fuels.
- compare fuels given appropriate data
How to calculate enthalpy of combustion in joules?
Q = m x c x ^T
How to find enthalpy of combustion in KJ?
^H = m x c x ^T/1000
How to find enthalpy of combustion in KJ/g (specific energy)?
- Find enthalpy in KJ
- ^H(KJ)/MW
How to find enthalpy in KJ/L (energy density)?
- Find ^H in KJ
- ^H/MW x p (density)
How to find enthalpy of combustion (KJ/mol)?
Q = m x c x ^T/1000 x n
What is photosynthesis?
- A natural process carried out by plants and micro-organisms which converts carbon dioxide and water to glucose and oxygen.
sunlight + chlorophyll in leaves
6O2(g) + 6H2O(l) -> C6H12O6(s) + 6O2(g) ^H = +2802 KJ/mol - This is an endothermic reaction
What is respiration?
- Releases chemical energy stored in the covalent bonds of carbohydrates and lipids.
- Reverse of photosynthesis.
C6H12O6(s) + 6O2(g) -> 6CO2(g) + 6H2O(l)
^H = -2802 kJ/mol - Energy is released, therefore is an exothermic reaction.
Occurs within the mitochondria and is vital for growth, repair, and metabolic processes.
Describe traditional energy generation.
- Burning coal and natural gas
- The combustion processes (exothermic) releases energy to heat the water which produces steam.
The movement of steam drives a turbine which in turn generates electricity using electromagnetic properties.
What is an alternative to steam turbines in producing electricity?
- Photovoltaic cells (solar cells)
Describe what photovoltaic cells are and their advantages and disadvantages?
- They convert sunlight to electricity directly.
ADVANTAGES:
- Doesn’t generate GG in operation
- Is a renewable energy source.
DISADVANTAGES:
- They produce zero pollution, however the process of production of these solar cells results in a lot of carbon emissions which is pollution.
List the disadvantages and advantages of steam turbines.
DISADVANTAGES:
- Produces CO2 which is a greenhouse gas molecule.
ADVANTAGES:
- Cheap and there are readily fuels.
- Is a renewable energy source.
List the disadvantages and advantages of steam turbines.
DISADVANTAGES:
- Produces CO2 which is a greenhouse gas molecule.
ADVANTAGES:
- Cheap and there are readily fuels.
- Is a renewable energy source.
What is oxidation?
- loss of electrons
- increase in oxidation number
What is reduction?
- gain of electrons.
- reduction in oxidation number
What is an oxidant?
- A species that brings upon oxidation
- It itself is being reduced.
What is a reducing agent?
- A species which brings upon reduction.
- It itself is therefore oxidised.
In a galvanic cell, where does oxidation occur?
- The anode.
What are fuel cells and their advantages?
- A device that converts chemical energy of a fuel and some oxidant into chemical energy.
- Similar to batteries (galvanic cells) as they convert chemical energy to electrical energy.
HOWEVER:
ADVANTAGES ARE: They don’t run down or require charging and they will produce electricity consistently as long as the fuel source and oxidant are continuously supplied.
Describe hydrogen fuel cells.
-They use the chemical energy of hydrogen to cleanly produce electricity.
- At the anode oxidation is occurring and is oxidizing hydrogen gas which produces electrons that move to the cathode, generating an electrical current.
- At the cathode reduction is occurring and the electrons generated at the anode travel to the cathode where reduction converts O2 molecules to water (H2O).
What are batteries?
- Two or more galvanic cells converting chemical energy to electrical energy.
- Their primary function is to to store and release electrical energy.
- Oxidation/reduction reactions create an electrical potential difference.
- There are two types of batteries, primary cells, and secondary cells.
What are primary cells?
- A non-rechargeable battery.
- Reactions which occur at the anode and cathode are non-revisable
- Once the anode has been completely consumed, the cell stops producing potential difference (in volts), therefore no longer produces a current for the electricity.
- Examples include mercury, alkaline, and zinc carbon.
What are secondary cells?
- Rechargeable batteries that transform chemical energy into electrical energy by a revisable redox reaction.
- Revisability of the anode and cathode allows the cell to be recharged using direct current electricity.
- Two types of reactions occur called charging and discharging.
- Examples include nickel-cadmium and lead-acid.
Where do electrons flow in a battery upon discharge?
- Anode to cathode where the anode is negative and the cathode is positive.
Where do electrons flow during recharge of a battery?
- The anode and cathode reverse their charge so the cathode becomes negative and anode becomes positive.
- Therefore electrons still flow from anode to cathode.
What are the advantages of fuel cells compared to batteries?
- Both are low in cost, and have high reliability.
BUT; fuel cells: - have low maintance (they don’t need replacing just a constant supply of the fuel and the oxidant)
- Low pollution
- And have a long life (infinite upon constant supply of required elements).
Describe flow cells.
- They are rechargeable fuel cells that can be used to store power (i.e wind and solar).
- They can undergo charging and discharging due to revisable redox reactions. Charging converts electrical energy to chemical energy and discharging converts chemical energy to electrical energy.
Describe the set-up of a flow cell.
- Two electrolyte solutions are separated by a proton exchange membrane which is only permeable to the flow of electrons and protons. Therefore, it stops the solution from mixing.
What are the advantages of flow cells over fuel cells?
- They have an unlimited capacity because the electrolytes are stored externally, therefore have wide potential for use.
- The cells are rechargeable so the electrolyte solutions can be used indefinitely.
- It can be discharged for extended periods of time and recharged indefinitely without loss of output.
- No emissions of atmospheric pollutants during operation.
- Components of the cell can be laid out in varying configurations (ie. tanks can be buried and stored underground).
Why is hydrogen being looked at as a fuel source?
- It has the highest energy density per gram and combustion only yields water by the following reaction:
H2(g) +1/2O2(g) -> H2O(l) ^H = -268 kJ/mol
What is the issue in using hydrogen as a potential fuel source and what are the advantages?
- Hydrogen is a flammable gas, therefore storage is an issue.
Currently, we lack the infrastructure to support the manufacture and distribution of hydrogen based electricity.
ADVANTAGES:
- Does not produce carbon dioxide - no GHE
- Can be used a fuel source for vehicles - further reducing emissions of GHG’s from the transport sector.
Hydrogen can also act as a reductant, reducing iron oxide to iron. Removing the need for coal-based iron production, reducing coal demand.
What are the different methods of Hydrogen production?
- Steam methane reforming (SMR)
- Biomass Gasification
- Electrolysis of Seawater
Describe steam methane reforming (SMR) in the production of hydrogen and its associated advantages and disadvantages.
- Heats methane obtained from natural gas (from fossil fuels) in the presence of steam and a catalyst.
Following the reaction equation:
CH4(g) + H2O(g) <-> CO(g) + HH2(g)
ADVANTAGES:
- Large-scale production
- Existing infrastructure and processes as used for the production of most hydrogen world wide.
DISADVANTAGES:
- Produces carbon monoxide.
- Uses non-renewable natural gas.
- Requires constant heating supplied by fossil fuel combustion.
Describe biomass gasification in the production of hydrogen and its associated advantages and disadvantages.
- A controlled process that uses heat, steam and oxygen to convert biomass to hydrogen and other products.
- Steam reacts with carbon organic compounds to produce carbon monoxide and hydrogen.
C(s) +H2O(l) <-> CO(g) H2(g)
ADVANTAGES:
- The GGE are much lower as biomass removes carbon dioxide from the atmosphere during growth.
DISADVANTAGES:
- Produces carbon dioxide.
Describe electrolysis of seawater during hydrogen production and its associated advantages and disadvantages.
- An electrical current is applied at the cathode, which results in the reduction of water by the following equation:
H2O(l) + 2e- -> H2(g) +2OH-(aq) - Requires an energy input much higher than the energy output of hydrogen.
ADVANTAGES:
- An inexhaustible source of the reactant.
- If this energy is produced from a renewable source (solar or wind) this process produces green hydrogen, and is considered a renewable source.
DISADVANTGES:
- Hydrogen extraction requires a higher energy input than energy released during hydrogen combustion.
- High energy input is very costly.
- If this required energy is produced from fossil fuels, this process is both environmentally and financially costly.
Define metal reactivity.
- How easily something undergoes oxidation.
- Metals higher in the metal reactivity series will displace metals lower in the reactivity series from their compounds.
The reactivity of METAL IONS (how easy metal ions are oxidized) is the reverse of the reactivity series.
When placing a iron nail in copper sulfate solution, a copper coating covers the iron nail and the solution changes from a blue to green. Why?
- Iron is higher on the metal reactivity series, therefore is more likely to be oxidized into is ion form turning the solution from blue to green.
- If iron is being oxidized, copper is being reduced, therefore is the reasoning for the copper coating on the iron nail.
What is sacrificial protection?
- To prevent the formation of iron oxide (rust) on ships, a zinc bar is used.
- This is because zinc is higher than iron in the metal reactivity series, therefore will be oxidized FIRST.
- Once consumed, the zinc bars can be easily replaced to further protect iron components within the ships.
- This same concept is used within the process of galvanization.
