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Managing Resources Flashcards

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1
Q

What classifies a source as renewable?

A

Renewable energy is generated over time scales of years to decades, from sources that are replenished much more quickly than fossil fuels.

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2
Q

What are examples of renewable sources?

A
  • Biofuels such as bioethanol and biodiesel
  • Sunlight
  • Wind
  • Geothermal
    -Hydroelectric
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3
Q

How are fossil fuels formed?

A

Fossil fuels (coal, petroleum and natural gas) form over geological time scales by anaerobic (without oxygen) decomposition of dead organisms under metamorphic conditions.

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4
Q

Why are fossil fuels non-renewable sources?

A

The reserves are depleted more quickly than they can be formed. It takes years to form fossil fuels.

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5
Q

Do we currently rely more on renewable or non-renewable sources?

A

We are still heavily dependent on non-renewable sources.

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6
Q

What is the photosynthesis equation?

A

6CO2 + 6H2O → C6H12O6 + 6O2

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7
Q

What do fossil fuels and biofuels provide energy for?

A

They are the feedstock (chemical manufacture of products) for the chemical industry.

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8
Q

Why does combustion create energy?

A

The energy resulting in combustion of fuels is from a release in energy stored within the bonds allowing for energy generation.

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9
Q

What are Biofuels?

A
  • Produced by present-day biological processes.
  • Derived from biomass (organic matter from plants) and waste matter from animals
  • Consists of bioethanol, biodiesel and biogas
  • Considered a renewable source as it has a low production time scale. Takes minutes from animal waste but years for the production of plants and algae.
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10
Q

What is Bioethanol?

A
  • Ethanol can be considered an alternate fuel source to petrol. Using it instead would reduce the demand of petrol (fossil fuels).
  • It can be blended with petrol or used as a pure fuel source.
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11
Q

How is Bioethanol produced?

A

It is produced by fermentation of simple carbohydrates (glucose) by microorganisms (yeast).

Or it can be produced indirectly from hydrolysis of complex carbohydrates (sugars). These sugars (polysaccharides) are hydrolysed using enzymes.

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12
Q

Describe the process of producing bioethanol with microraganism.

A

It is an anaerobic process:
C6H12O6(aq) -> 2C2H5OH(l) + 2CO2(g) deltaH = -ve kJ/mol

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13
Q

Describe the process of producing bioethanol through hydrolysis

A

(C6H10O5)n (aq) + nH2O(l) -> nC6H12O6(aq)
to hydrolyze

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14
Q

How to filter bioethanol?

A

Fractional distillation can be used to separate the ethanol from the reaction mixture based on boiling point, increasing the concentration and purity of the bioethanol obtained

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15
Q

What is biodiesel?

A

It is an alternate to petroleum diesel and can be easily incorporated into diesel blends.
It is derived from triglycerides sources from animal fates, oils and plants ang algae.

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16
Q

What is combustion?

A

It is a reaction between a fuel and an oxidant (oxygen) that occurs at high temperatures.

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17
Q

What is the word equation for complete combustion

A

hydrocarbon + oxygen -> carbon dioxide and water

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18
Q

What are the two types of incomplete combustion?

A

One results in the partial oxidation of carbon to CO.
The second is partial oxidation of carbon to soot.

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19
Q

Why does incomplete combustion occur?

A

Incomplete combustion occurs as a result of insufficient oxygen.

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20
Q

What are some causes of incomplete combustion?

A

When fuel is combusted in industrial furnaces and in combustion engines.
Larger hydrocarbon chains are more likely to result in incomplete combustion.

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21
Q

Why does increasing chain length increase likelihood of incomplete combustion?

A

As the length of the carbon chain increases, the ration of carbon to oxygen increases, limiting the availability of oxygen to form carbon dioxide.
Larger molecules have stronger dispersion forces making them less volatile fuel sources. Reduces the ability to mix effectively with gaseous oxygen during combustion.

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22
Q

What are the effects of carbon monoxide?

A

Carbon monoxide binds to haemoglobins, the molecule used to transport oxygen within the blood.
Hb(O2)4 + 4CO <-> Hb(CO)4 + 4O2.
It binds more strongly than oxygen, shifting the equilibria of the reaction to the right, decreasing oxygen transport around the body.
Low concentrations of CO can cause fatigue and dizziness.
Large concentrations of CO can cause loss of consciousness and death.

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23
Q

What are the effects of soot?

A

Soot is a complex aggregate of carbon nanoparticles.
It can limit visibility in urban areas, blackening surfaces causing visual pollution.
Can be inhaled causing respiratory illnesses and difficulties.
Can cover leaves of plants reducing photosynthesis and stunting growth.
Due to the black colour, it can absorb solar radiation causing localised warming (responsible for melting of ice and snow, further contributing to global warming).

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24
Q

Why are hydrocarbons with a higher degree of unsaturation more likely undergo incomplete combustion?

A

As chain length or unsaturation (more double and triple bonds) increase, the ratio of carbon to oxygen increases leading to a decrease in the number of oxygens available to form carbon dioxide
Molecules with higher molar mass experience stronger intermolecular dispersion forces, resulting in higher boiling point and limiting its ability to mix with gaseous molecules.

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25
Q

What is enthalpy if the reaction is endothermic?

A

Positive (products higher than reactants)

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26
Q

What is the enthalpy if the reaction is exothermic?

A

negative (reactants higher than products)

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27
Q

Which of endo and exothermic is easier to complete?

A

Exothermic is easier as there is less activation energy.

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28
Q

What is calorimetry?

A

The measurement of heat energy changes during a chemical reaction or change of state.

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29
Q

What is a calorimeter?

A

An insulated reaction vessel designed to measure energy changes (heat loss or gain) with no (or minimal) heath loss to the surroundings.

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30
Q

What is a bomb calorimeter?

A

An insulated reaction vessel designed to measure enthalpy for combustions of solid and liquid fuels.

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31
Q

Describe the accuracy of bomb calorimetry

A

Bomb calorimetry is a highly accurate techniques when compared to known molar enthalpy of combustion values.

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32
Q

What is the process of bomb calorimetry?

A

The bomb is pressurised with oxygen gas and the weighed pellet of fuel is combusted via an ignition fuel.

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33
Q

What is the role of the stirrer in bomb calorimetry?

A

It disperses heat within the water, ensuring even temperature.

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34
Q

What are errors within bomb calorimetry?

A

Incomplete combustion - resulting in less energy released.
Heat released from combustion is being absorbed by other mediums (metal or air or oxygen inside)
Release of heat from combustion is not instantaneous - some heat may be absorbed by the water, which is further lost by the air.
Depending on the fuel, mass may change overtime (evaporation)

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35
Q

What is the equation for quantity of heat released within combustion?

A

Q = m x c x ^T (joules)

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36
Q

What is the molar enthalpy of combustion equation?

A

^H = m x c x ^t/1000 x n
(kJ/mol)

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37
Q

What makes one fuel better than another?

A

Fuels with higher molar enthalpy of combustion energy can be considered a better fuel source.

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38
Q

How to converto heat released per gram

A

^H/MW (kJ/g)

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39
Q

To convert to heat released per litre

A

^H/MW x density (kJ/L)

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40
Q

What would be a consequence of choosing a fuel source that has a lower energy density?

A

More fuel would be required to reach a higher energy output. This would increase the amount and cost of resources required to produce the fuel source.

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41
Q

What is photosynthesis and respiration?

A

They are important processes in the cycling of carbon and oxygen on Earth.

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42
Q

What is photosynthesis?

A

Photosynthesis is a process carried out by plants and micro-organisms such as plankton, algae and cyanobacteria.
It converts carbon dioxide, water and light energy (in the form of sun) into glucose (a form of chemical energy) and oxygen.

6CO2(g) + 6H2O(l) -> (energy) C6H12O2(g) + 6O2(g) ^H = -2802kJ/mol.
This is an endothermic process (positive enthalpy), in which the absorption of energy (sunlight) is done by chlorophyll.

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43
Q

What are the advantages of photosynthesis?

A

It reduces the CO and CO2, reducing the greenhouse effect.

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44
Q

Why does destroying trees contribute to to our atmospheric greenhouse gases?

A

Destroying trees means there are less places to store CO2 which means we are burning it more and storing it in our atmosphere.

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45
Q

What is respiration?

A

It is a reaction carried out by all living things to release chemical energy stored in the covalent bonds of carbohydrates and lipids.
C6H12O6(s) + 6O2(g) -> 6CO2(g) +6H2O(l) ^H = -2802kJ/mol
This reaction is releasing energy (exothermic reactions).
Occurs within the mitochondria.

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46
Q

How is most of Australia’s energy generated?

A

Through burning of coal and natural gas.

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47
Q

What is the method of a steam turbine?

A

The combustion process (exothermic) releases energy to heat the water producing steam
The movement of steam drives a turbine which in turn generates electricity using electromagnetic proprieties.
The faster the turbine spins the more energy produced.
This is an exothermic reaction.

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48
Q

What is a disadvantage of steam turbines?

A

It is fuelled using fossil fuels
producing CO2.

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49
Q

What are solar cells?

A

Photovoltaic Cells

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50
Q

What is the process of photovoltaic cells?

A

Photovoltaic cells work to convert sunlight directly into electricity.

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51
Q

What are the advantages of photovoltaic cells?

A

Produces no pollution when operating
Low start up cost
Renewable

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52
Q

What are disadvantages of photovoltaic cells?

A

During production of cells carbon emissions are produced
They take up lots of land.
Don’t work during the night
Prone to breaking due to weather

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53
Q

What are the advantages of steam turbine?

A

Cheap and readily fuels
Renewable energy source

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54
Q

What is a redox reaction?

A

A redox reaction is a chemical process that involves the transfer of electrons.

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55
Q

What are the oxidation number rules? (in order)

A

The oxidation number for any free element is always 0
The oxidation number of monatomic ion equals the charge of the ion (including the sign)
The usual oxidation number of hydrogen is +1 (in compounds containing elements that are less electronegative than hydrogen it is -1)
The oxidation number of oxygen is -2 (exceptions do apply)
The oxidation numbers of group 1, 2 and 7 elements are +1, +2 and -1 respectively (exceptions do apply)
The sum of oxidation numbers of all elements within a neutral compound is 0
The sum of the oxidation numbers in a polyatomic ion (ions containing multiple elements) is equal to its charge

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56
Q

What is an oxidant?

A

Is a species that is reduced but brings upon oxidation.

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57
Q

What is a reductant?

A

A species that in it self is oxidised but brings upon reduction.

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58
Q

What is a fuel cell?

A

A fuel cell is a device that converts the chemical energy of a fuel (hydrogen, natural gas, methanol) and some oxidant into electrical energy.
Fuel cells are similar to batteries (galvanic cells that convert chemical energy into electrical energy). However, fuel cells do not run down or require charging. And will produces electricity as long as a source of fuel and a source of an oxidant are supplied.

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59
Q

What kind of cells are fuel cells?

A

Galvanic cells as they require a consistent flow of reagents to enable electricity generation.

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60
Q

Why are fuel cells considered renewable?

A

If you consistently supply fuel, the cell with continuously provide power. This source could be infinite if enough fuel was supplied.

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61
Q

What is a hydrogen fuel cell?

A

Hydrogen fuel cells use the chemical energy of hydrogen to cleanly produce electricity.

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62
Q

What is a disadvantage of fuel cells?

A

Expensive to manufacture due the high cost of catalysts. Hydrogen is expensive to produce and not widely available.

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63
Q

Describe the process of a hydrogen fuel cell…

A

The oxidation occurs at the anode, the hydrogen gas is oxidised, producing electrons that move to the cathode generating an electrical current.
The electrons generated at the anode, flow to the cathode where reduction occurs converting protons and oxygen to water.
The flow of electrons allows for the generation of current.

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64
Q

Advantages of a hydrogen fuel cell?

A

Cleanly produces energy
Produces water which is a green house gas but not a horrible one
Has the highest energy density per gram

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65
Q

What are the disadvantages of a hydrogen fuel cell?

A

The Hydrogen gas is flammable
It produces water which is a green house gas.

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66
Q

What are the equations for a hydrogen fuel cell?

A

Anode: H2 -> 2H+ + 2e-
Cathode: 1/2O2 + 2H+ +2e- -> H2O
Overall: H2 + 1/2O2 -> H2O

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67
Q

What is the energy conversion of a galvanic cell?

A

Chemical energy to electrical energy

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68
Q

Draw a galvanic cell

A
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69
Q

What is a battery?

A
  • A battery consists of two or more galvanic cells
  • the cells are connected in a series arrangement
  • they transform chemical energy into electrical energy
  • their primary function is to store and release electrical energy
  • the oxidation and reduction reactions create an electrical potential difference
  • drives the flow of electrons from anode to cathode
  • there are two types
    primary and secondary cells
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70
Q

What are the properties of a primary battery cell?

A
  • Non -rechargeable
  • Designed to be used only once
  • The reactions occurring at the anode and cathode are non-reversible
  • Once the anode has been consumed, the cell stops producing a potential difference, therefore it no longer produces a current.
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71
Q

What are three different types of primary cell batteries?

A

Mercury, alkaline and zinc carbon

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72
Q

What are the properties of a secondary battery cell?

A
  • They’re are rechargeable
  • They transform chemical energy into electrical energy by a redox reaction that is reversable.
  • The reversibility of the anode/cathode reactions allow the cell to be recharged using direct current (DC) electricity.
  • Two types of reactions occur, discharging and recharging.
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73
Q

What are two different types of secondary batteries?

A

Nickel-cadmium and lead-acid.

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74
Q

What are the advantages of batteries?

A

Low cost
High reliability

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75
Q

What are the disadvantages of batteries?

A

They need replacing, they run down, they pollute and they don’t have a long life

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76
Q

What are the advantages of fuel cells?

A

Low cost
High reliability
low maintenance
long run time
low pollution
long life

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77
Q

What is a flow cell?

A

They are rechargeable fuel cells that can be used to store power (wind and solar)
They can be charged (electrical energy to chemical energy) and discharged (chemical energy to electrical energy) via reversible redox reactions. (secondary batteries)

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78
Q

Describe the process of a flow cell…

A

Two electrolyte solutions are separated by a proton exchange membrane which only allows for the flow of electrons and protons, preventing the solutions from mixing.
Increasing the size of the membrane will increase the rate of charging and discharging

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79
Q

What are the equations for a flow cell during charging?

A

Cathode: Zn2+ + 2e- -> Zn (reduction)
Anode: Ce3+ -> Ce4+ + e-
(oxidation)

80
Q

What are the equations for a flow cell during discharging?

A

Anode: Zn -> Zn2+ + 2e- (oxidation)
Cathode: Ce4+ + e- -> Ce3+ (reduction)

81
Q

What are the advantages of flow cells over fuel cells?

A
  • Unlimited capacity - electrolytes are stored externally therefore wide potential for use.
  • Cells are rechargeable - meaning that the electrolytes can be used indefinitely
  • Can be discharged for extended period and recharged indefinitely without loss of output
  • No emissions contributed to the atmosphere during operations
  • Components of a cell can be laid out in carrying configurations - can be buried and stored within tanks underground
  • the bigger the tank the more energy meaning
82
Q

Disadvantages of flow cells

A

The membrane can decay this is the expensive part.

83
Q

What are the three methods of hydrogen production?

A

Steam methane Reforming (SMR)
Biomass Gasification
Electrolysis of seawater (clean)

84
Q

What is Steam Methane Reforming?

A

It is a process that heats methane obtained from natural gas (from fossil fuels) in the presence of steam and a catalyst.
CH4(g) + H2O(g) <-> CO(g) +3H2(g)
Therefore this is not a clean method to produce hydrogen gas.

85
Q

What are the advantages of steam methane reforming?

A
  • Large scale production
  • Existing infrastructure and processes is used for the production of most hydrogen world-wide
86
Q

What are the disadvantages of steam methane reforming?

A
  • Produces carbon monoxide
  • Uses non-renewable natural gas
  • Requires constant heating supplied by fossil fuel combustion
  • Uses fossil fuels
87
Q

What is Biomass Gasification?

A

It is a controlled process that uses heat, steam and oxygen to convert biomass to hydrogen and other products.
The steam reacts with carbon organic compounds to produce carbon monoxide and hydrogen.
C(s) + H2O(g) -> CO(g) +H2(g)
Not a clean source as it produces carbon monoxide.

88
Q

What are the advantages of Biomass Gasification?

A

Lowers green house emissions as the biomass removes carbon dioxide from the atmosphere during growth
Cleans up our rubbish as the soot is a result of dead matter

89
Q

What are the disadvantages of Biomass Gasification?

A

Produces carbon monoxide

90
Q

What is electrolysis of seawater?

A

Seawater has the potential to produce hydrogen gas from an essentially inexhaustible supply.
Electrolysis of seawater requires an energy input that is much higher than the energy output from hydrogen.
An electrical current is applied at the cathode, resulting in the reduction of water.
H2O(l) + 2e- -> H2(g) +2OH-(aq)
This cleanly produces Hydrogen gas.

91
Q

What are the disadvantages of electrolysis of seawater?

A

If the energy needed for the reaction is produced through fossil fuels, this process is both environmentally and financially costly.
The energy is coming from fossil fuels.

92
Q

What are the advantages of electrolysis of seawater?

A

If the energy needed is produced through a renewable source (solar or wind), this process produces green hydrogen and is considered a renewable source.

93
Q

What is the process of water treatment?

A

The treatment of water depends on its raw source: depending on location impurities and it depending on its intended use will change the level of purification.

94
Q

What is the process of water treatment?

A
  1. Coagulation
  2. Flocculation
  3. Sedimentation
  4. Filtration
  5. Disinfection
  6. Fluoridation
95
Q

What is sedimentation in water treatment?

A

It is the settling of the floc aggregates.

96
Q

What is filtration in the process of water treatment?

A

it is the removal of solid impurities, it is done through passing dirty water through layers of sand and charcoal.

97
Q

What is disinfection in the process of water treatment?

A

It is the removal of any biological contaminants.

98
Q

What is fluoridation in the process of water treatment?

A

It is the controlled adjustment of fluoride content within water.

99
Q

What is coagulation in the process of water treatment?

A

It is the chemical process of neutralising the surface charge of particles.

100
Q

What is Flocculation in the process of water treatment?

A

It is the physical process of clustering (aggregation) of impurity particles.

101
Q

What are the main water impurities within a fresh water source?

A

Due to the presence of weathering of rocks, suspended inorganic (non-carbon containing) solids are found within water.
These include clays - aluminosilicate minerals composed of aluminium silicon and oxygen.
Clay particles have particle sizes in the micrometre range, making them difficult to remove.

102
Q

What microorganisms are considered impurities within water?

A

Dirt, ions, heavy metals, high concentration of fertilisers and rocks.

103
Q

What are the three particle sizes?

A

True solution less than 10^-7
Colloidal solution between 10^-7 and 10^-5
Suspensions particles 10^-5

104
Q

Describe the process of increasing particle size of water impurities…

A

A true solution (a substance that is homogenously dispersed within another substance, i.e water) has a particle size in the nanometre to micrometre range. Within the water, clay particles form a colloidal suspension due to particle sizes in the micrometre range. Anything with particle size greater than 10^-5cm, is considered a suspension.
Increasing the particle size of the impurities will cause them to drop to the bottom because of gravity, these can then be poured out.

105
Q

Why is sea water undrinkable?

A

The high content of sodium chloride within sea water, is undrinkable. The amount of sale within sea water is much higher than what can be processed by the human body.

106
Q

What is the desalination method of reverse Osmosis?

A

Reverse osmosis is used to remove a solute. Pressure is applied to the side with higher salt concentration. This overcomes the osmotic pressure (spontaneous movement of water due to osmosis). The water passes through the semi-permeable membrane but the solute (salt) remains trapped on the other side.
The pressure applied to the salt water, the water moves from low to high concentration leaving the salt on one side, allowing for the fresh water to be retrieved.

107
Q

Advantages of reverse osmosis and thermal distillation

A
  • It is an easy process
  • Produces Potable water
  • Abundant amount of seawater can be used to lower the demand of fresh water supplied
  • This process is not effected by climate (drought)
108
Q

Disadvantages of reverse osmosis

A
  • Not cheap due to the pressure which is dangerous so the specialised equipment needed is costly.
  • To maintain the pressure is also costly.
  • requires a large amount of energy
  • generation of brine as a waste product needs disposing
  • The heat generated can affect local ecosystems
109
Q

What is thermal distillation?

A

Saline water is heated until boiling and the pure water vapour is condensed and collected.

110
Q

Describe the method of thermal distillation

A

The sea water is heated this produces steam, fractional distillation meaning salt does not go as well. The water vapour is then cooled resulting in condensation which drops as potable water which can be extracted.

111
Q

What are further impurities after desalination?

A

Cyanobacteria can lead to algal infections
Cholera to an estimated 143000 deaths yearly
These are all waterborne infectious bacteria
Thermal distillation would be the only process to remove this

112
Q

Why do plants need nutrients from soil?

A

Plants require nutrients for growth and to carry out normal cellular processes such as photosynthesis, respiration and reproduction.

113
Q

How do plants intake their nutrients?

A

Plants (assimilate) take up nutrients as water soluble ions present in the soil solution (water in the soil) via their root system.
If it is not water soluble it cannot act as a plant nutrient as water is good at dissolving ions because they are charged, which results in dipoles allowing for the ions to be absorbed.

114
Q

What elements do plants require for their nutrients?

A

Nitrogen - required for synthesis of amino acids, proteins, enzymes, DNA, RNA and chlorophyll
Phosphorous - required for the synthesis of DNA, RNA, phospholipids (the building blocks of the cell membrane), and ATP - cells energy currency
Potassium - regulates water transport and opening and closing of the stoma (gas exchange pores)

115
Q

What are the ions that are soil nutrients for plants?

A

Nitrate ion (NO3-)
Ammonium ion (NH4+)
Hydrogen Phosphate ion (HPO42-)
Dihydrogen Phosphate ion (H2PH4-)
Potassium ion (K+)
Calcium ion (Ca2+)
Magnesium ion (Mg2+)
Sulfate ion (SO42-)

116
Q

What is Nitrogen fixation?

A

N2 must be fixed (converted into a more useful form) before it can be used by living things e.g. N2 must be converted into soluble ions before it can be assimilated (uptake/absorbed via roots) by plants.
Nitrogen fixation can be achieved by either natural or synthetic processes.

117
Q

Why must nitrogen be fixated?

A

Nitrogen gas, N2, makes up 78% of the atmosphere. It is a relatively stable and inert molecule due to the presence of a string triple covalent bond between the nitrogen atoms.
To split the N2 bonds large amounts of energy is required, often provided through lightening and volcanoes. This then allows it to be absorbed into the dirt

118
Q

Describe the natural processes of nitrogen fixation

A

Lightning, volcanos and forest fires provides sufficient energy (high temperatures) to break the strong N2 covalent triple bond, allowing it to react with atmospheric oxygen and form nitrogen oxides.

N2 + O2 -> 2NO (nitric oxide)
2NO + O2 ->2NO2 (nitrogen dioxide)
Nitrogen dioxide then dissolves in water vapour in the atmosphere forming nitrous acid (HNO2) and nitric acid (HNO3)
2NO2 + H2O -> HNO2 + HNO3

119
Q

Describe the process of the ionisation of nitric and nitrous acid (natural nitrogen fixation)

A

Both of the acids ionise producing soluble nitrate ions (NO3-) and nitrite ions (NO2-) which are deposited into the soil during rain fall.
HNO3 + H2O → H3O+ + NO3- (full ionisation – strong acid)
HNO2 + H2O ⇌ H3O+ + NO2- (partial ionisation – weak acid).

120
Q

Describe the process of the decay of nitrogen containing organisms

A

Nitrogen containing compounds can also enter the soil through the waste (excrement) from living animal and plants.
- when deceased animals and plants start to decay (complex organic molecules e.g. polymers, DNA broken down by bacteria into simpler, smaller molecules and ions).
- Aerobic decay (O2 present, breakdown products exist in their maximum oxidation state): N containing compound -> NO3- (nitrate ion).
- Anaerobic decay (complete absence of O2, breakdown products exist in their minimum oxidation state): N containing compound -> NH3 (ammonia).
This process increase nitrogen content within the soil.

121
Q

Describe the process of nitrification

A

Nitrifying bacteria in the soil oxidise ammonia (NH3) and ammonium ions (NH4+) into nitrite ions (NO2-) and nitrate ions (NO3-).
NH3/NH4+ -> NO2- -> NO3-

122
Q

Describe the process of denitrification

A

Denitrifying bacteria in the soil reduces the nitrate ions (NO3-) to nitrogen gas under anaerobic conditions.
NO3- -> N2

123
Q

Describe the process of synthetic nitrogen fixation

A

The synthetic Haber process converts atmospheric nitrogen (N2) to ammonia (NH3) under high pressure and temperature.
N2 + 3H2 -> 2NH3

124
Q

Describe the effect of fertilisers

A

In a natural ecosystem, the rate at which plants uptake nutrients from the soil, should be balanced by the rate at which nutrients are returned to the soil via the process of decay e.g leaves falling in autumn.

125
Q

Why do humans rely on fertilisers?

A

Human life is dependent on crop farming to produce food and fuel. This farming depletes the soil of nutrients as the plants are grown and harvested i.e. no decay to replenish the soil of nutrients. Therefore, the soil becomes infertile and require fertilizers to be added to grow more crops

Fertilisers improve plant fertility by adding nutrients containing nitrogen, phosphorus and potassium (and other trace elements) into the soil.

126
Q

What are the two methods of fertilising?

A

Dry - Is dumping organic fertiliser and waiting for it to rain.
Wet - is using aqueous fertiliser.

127
Q

What is a natural fertiliser?

A

Natural fertilisers are broken down by decomposers (bacteria) in soil.
These include manure, compost, blood and bone and wood ash.

128
Q

What are artificial fertilisers?

A

Artificial fertilisers consist of nutrients within a water-soluble compounds and can be taken up by plants directly from fertilisers.
Ammonium nitrate/sulfate, urea, calcium dihydrogen, phosphate, potassium chloride.
Using artificial fertilisers means that they are not relying on there to be enough nutrients.
Artificial is used more because it is easier to access.

129
Q

What are disadvantages of fertiliser?

A

The use of fertilisers can lead to eutrophication, especially after periods of heavy rainfall.
Excess nitrogen and phosphorus from fertilisers, detergents (contain phosphate groups) or sewage can be leached from soils into waterways e.g. rivers and lakes causing eutrophication
The increase in available nutrients promotes the excessive growth of aquatic plants including photosynthetic microbes including; algae and bacteria. These microbes form a bloom which prevents sunlight from reaching into the waterway.
Aquatic plants underneath the bloom do not receive sunlight and are unable to photosynthesise causing them to die.
Aerobic bacteria decompose the dead plant matter, further depleting the oxygen supply in the water and causing the death of aquatic organisms (plants, fish etc.).
When the oxygen supply is fully depleted, anaerobic bacteria decompose the plant and animal remains generating products that are toxic to the water, making the water even less habitable for the remaining organisms.

130
Q

What is metal reactivity referring to?

A

How easily a metal undergoes oxidation.
The higher in the series a metal is, the the more likely it will displace the metals lower in the series (undergo oxidation). This is the reverse for the ion of that metal, which does not want to undergo reduction.

131
Q

Where is carbon in the metal reactivity series?

A

It is below aluminium and above zinc.

132
Q

What is sacrificial protection?

A

To prevent the formation of iron oxide (rust) on ships a zinc bar is used.
Zinc appears higher than iron in the metal reactivity series, will be oxidised first.
Once consumed, zinc bars can be easily replaced to further protect iron components within ships.
This same concept is used within the process of galvanization.

133
Q

What are consequences of metal reactivity?

A

Most metals are sufficiently reactive to be found within the Earth’s crust as minerals, a compound containing the metals and other elements (commonly oxygen and sulfur)
Some unreactive metals (Ag, Au, Pt) are found naturally in an uncombined state.
A deposit within the Earth’s crust where the concentration of a mineral is higher than usual is referred to as metal ore. Ores contain other minerals other than the metal mineral of interest (referred to as gangue).
When metals are mined (extracted from the crust) only metal ores with a high percentage of the metal/mineral of interest are economically viable to extract.
If found naturally they’re more likely to undergo reduction.

134
Q

What is the process of metal production?

A

Producing pure metals from their ores is a multi-step process that may involve
1. Extraction
2. Concentration
3. Conversion
4. Reduction
5. Refining

135
Q

What is extraction of metal production?

A

The removal of metal ore from the Earth’s crust.

136
Q

What is concentration in metal production?

A
  • The ore is crushed and ground.
  • Completed at mine site to reduce cost of transportation and rock disposal.
  • Removal of gangue to form mineral concentrate.
  • May not be required if mineral in ore was in high concentration or it is possible to remove mineral in presence of waste.
137
Q

What is conversion in the process of metal production?

A

It converts mineral to a compound that can be reduced, therefore is not required if compound can already be reduced. E.g chemical process like roasting the sulfide mineral to produce the metal oxide or sintering. The mineral is then leached with an acid to produce a sulfate, this solution is then filtered to remove any suspended solids. The powdered mineral is then added to precipitate any less reactive metal ions.

138
Q

What is reduction in metal production?

A

Depends on the reactivity of the metals but may include; molten electrolysis, aqueous electrolysis and chemical reduction via a chemical reducing agent.

139
Q

What is refining in metal production?

A
  • Remaining impurities can be removed by electrolysis or further chemical reactions if necessary.
  • Removing trace impurities (not required for Al or Zn).
140
Q

What is chemical reduction?

A
  • Blast furnaces used are held at temperatures of 1000 degree Celsius.
  • High temperatures are created and maintained by fossil fuels.
  • Produces large amounts of carbon dioxide.
141
Q

What is electrolytic reduction?

A
  • High temperatures are not required.
  • Energy and cost saving compared with chemical reduction or a molten cell.
    This is currently used for 90% of the worlds zinc production.
    Molten electrolysis is expensive.
142
Q

What are the other energy requirements of metal production?

A
  1. low energy steps of crushing, grinding, leaching and floatation.
  2. medium energy steps of roasting and heating
  3. high energy steps of reduction (blast furnace and electrolysis)(8-12kJ per tonne metal)
  4. highest energy steps electrolysis of molten electrolyte e.g Al (30-50kJ per tonne metal)
143
Q

What is metal recycling?

A

Recycling metals is becoming increasingly important to conserve finite resources.
- Over 50% of aluminium and lead are produced from recycled materials.
Recycling resources means they become finite slower as they do degrade but they can be used a few more times prior.

144
Q

What are the advantages of recycling metals?

A
  • Conserves finite resources: both metals and fossil fuels are used in the production of metals.
  • Reduces energy requirement: lower energy cost to recycle than produce from ores (roasting in furnace and undergoing reduction via electrolysis not required)
  • Reduces mining: mining is damaging the environment, creates waste materials e.g. gangue and is expensive
  • Reduces landfill: sulfur oxides (acid rain), nitrogen oxides (photochemical smog), soot (C), carbon monoxide (toxic gas) and greenhouse gases are all generated in the production of metal.
  • Reduces water materials: waste is harmful to the environment.
  • Reduced landfill: Recycling reduces the amount of waste products sent to landfill.
    If metals are recycled the demand of finite resources are elevated.
145
Q

Why and how do we recycle polymers?

A

Polymer (plastics) production has created an abundance of waste products.
- Polymers must be sorted before recycling based on both chemical and physical properties.

146
Q

What are the two methods of recycling polymers?

A

Physical (broken down by shredding or melting)
Chemical (broken down to be reused to make new polymers or used as fuels).

147
Q

What are the advantages of recycling polymers?

A

Conserves fossil fuels: most polymers are created from petroleum a finite fossil fuel feedstock.
Minimises energy requirement: lower energy cost to recycling than synthesise from scratch.
It reduces landfill: recycling reduces the amount of waste products sent to landfill.

148
Q

How are Thermoplastics recycled?

A

They contain dispersion forces or hydrogen bonding between the polymer chains.
These soften when heated, harden and become more rigid when cooled. They can be recycled by heating and reshaping.
They can be recycled many times until polymer chains decompose.

149
Q

Describe why Thermosets cannot be recycled?

A

They contain a high degree of cross-linking (covalent bonds).
They do not soften or change in shape when heated. They will char or burn if heated sufficiently as the covalent bonds break and the polymer decomposes. Therefore they cannot be recycling.

150
Q

What are composite materials?

A

They are formed by combining two or more materials that have quite different properties.
The different materials work together to give the composite unique properties, but within the composite you can easily tell the difference between the materials and they do not blend or dissolve into each other.
These are very strong materials and separating them is difficult.

151
Q

What is the structure of a composite material?

A

The composite material consists of two materials, a matrix and a reinforcement.
The matrix is the bulky material and the reinforcement is the material embedded throughout the matrix.

152
Q

What are example of composite materials?

A

Wood, mud bricks and concrete

153
Q

What are the advantages of composite materials?

A

Improved properties both materials can be utilised in comparison to their original materials.
Designed for specific use

154
Q

Describe the process of recycling composite materials?

A

Composite materials are harder to recycle than single component materials due to the mixing and incorporation of different components of the resulting material.
Most composite materials use thermosetting polymers as the matrix, therefore, they cannot be heated to separate the matrix from the reinforcement.

They can also be recycled using pyrolysis. This heats the composite material under oxygen to combust the thermoset polymers and retain the reinforcement fibres. This is limited due to high costs, low quality of separated components and lack of incentives and infrastructure.

155
Q

What are the two communication and collaboration SHE concepts?

A
  • Science is a global enterprise that relies on clear communication, international conventions, and review and verification of results.
  • International collaboration is often required in scientific investigation.
156
Q

What are the two Development SHE concepts?

A
  • Development of complex scientific models and/or theories often requires a wide range of evidence from many sources and across disciplines.
  • New technologies improve the efficiency of scientific procedures and data collection and analysis. This can reveal new evidence that may modify or replace models, theories, and processes.
157
Q

What are the two Influence SHE concepts?

A
  • Advances in scientific understanding in one field can influence and be influenced by other areas of science, technology, engineering, and mathematics.
  • The acceptance and use of scientific knowledge can be influenced by social, economic, cultural, and ethical considerations.
158
Q

What are the three Application and Limitation

A
  • Scientific knowledge, understanding, and inquiry can enable scientists to develop solutions, make discoveries, design action for sustainability, evaluate economic, social, cultural, and environmental impacts, offer valid explanations, and make reliable predictions.
  • The use of scientific knowledge may have beneficial or unexpected consequences; this requires monitoring, assessment, and evaluation of risk and provides opportunities for innovation.
  • Science informs public debate and is in turn influenced by public debate; at times, there may be complex, unanticipated variables or insufficient data that may limit possible conclusions.
159
Q

Why are hydrogen fuel cells so popular?

A

Hydrogen has the highest energy density per gram and combustion yields old water
H2(g) + 1/2 O2(g) -> H2O(l) ^H=-286kJ/mol
This process does not produce carbon dioxide reducing contributions to the green house effect.
Can also be used as a fuel source for vehicles - further reducing emissions from the transport sector.
Also, hydrogen can also act as a reductant, reducing iron oxide to iron. Removing the need for coal-based iron production. further reducing coal demand.

160
Q

What are the disadvantages of hydrogen fuel cells?

A

Hydrogen is incredibly flammable, so storage is an issue.
We lack the infrastructure to support the manufacture and distribution of hydrogen based electricity.

161
Q

How is the particle size of water impurities increased?

A

Coagulation is done by neutralising the surface charge by adding salts of highly charged cations (Al3+) and/or charged polymers to the solution which are attracted to the negatively charged clay particles, neutrilising the negative charge. This occurs as like charges repel. The suspension becomes destabilised and dispersions forces allow particles to aggregate, joining them together in layers to create large sized particles of clay called microflocs. These microflocs, are not soluble in water and eventually settle at the bottom. Allowing for it to be agitated, forming a floc, due to its larger particle size and mass it settles at the bottom of the container to be removed as sediment.

162
Q

What is feedstock?

A

A feedstock is a raw material used to provide reactants for an industrial reaction.

163
Q

What is electrolysis in metal production?

A

The same as electrolytic cells, pushing a reaction in a non spontaneous reaction.
Electrolysis is commercially important as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell. Reduces the ion to its pure metal.

164
Q

What are the three natural processes of nitrogen fixation?

A

Nitrogen fixing bacteria
Decay of dead animals
Natural nitrogen fixation which needs high energy (acid rain equations and similar process).

165
Q

What is roasting in metal production?

A

A process of conversion, which uses oxygen and high energy.

166
Q

What is leaching in metal production?

A

Uses an acid to leach out the metal which is then produces zinc sulphate.

167
Q

What is the chemical formula for an biodiesel e.g ethanol

A

Normal carbon amount, normal hydrogen plus an oxygen eg C2H5OH

168
Q

What is a transesterification reaction

A

It is the process of reacting, triglycerides with an alcohol to produce esters and glycerol. in the presence of a catalyst

169
Q

What happens in a transesterification reaction?

A

The replacement of the alkyl group of an ester by another through interaction of the ester and alcohol

170
Q

What is a technique to determine the concentration of a metal with an ore?

A

AAS

171
Q

What does a frothing agent do in the concentration of a mineral?

A

It causes the water to bubble and froth up causing the mineral to separate and removed.

172
Q

What is the role of a collector in the concentration process of mineral production?

A

It is an ion that contains a charged (anionic) region and a non-polar region e.g hydrocarbon chain. This forms a thin hydrophobic layer over the surface of minerals, increasing their floatability.

173
Q

Describe the steps of froth floatation in metal production…

A
  1. The powdered mineral and gangue are mixed with water to form a slurry.
  2. Frothing agents and collectors are added.
  3. Air is blown through the slurry and it is stirred to create bubbles which the minerals attach to and float to the surface.
  4. Froth containing the mineral is skimmed off and excess water is removed.
  5. Waste gangue sink to the bottom.
174
Q

Describe how minerals attach to the collectors in metal concentration

A

The anionic region adsorbs to the surface of the mineral powder through ionic interaction.
The nonpolar region attaches to the air bubble which rise to the surface of the slurry and carry the mineral up because it is hydrophobic.

175
Q

Why must a mineral be converted to a soluble molecule in metal production?

A

The mineral must be converted into a soluble molecule in order for it to undergo reduction via electrolysis.

176
Q

List the reduction processes for the parts of the reactivity series.

A
  • everything above water (Al and above) is done by molten electrolysis as water would be reduced preferentially to the metal ions
  • Zinc is chemical reduction ot electrolysis of an aqueous salt
  • Between iron and lead is chemical reduction
  • Copper and Hg is roasting
  • gold and silver are found uncombine.
177
Q

What are the disadvantages of using carbon-based fuels as a feedstock?

A

Carbon materials are finite, so if it is used in feedstock, less is available to use to generate plastics and produce metal.
This will increase the green house gases with the atmosphere.

178
Q

What is the chemical formula for a triglyceride?

A

C6H8O7

179
Q

What is the chemical formula for glycerol?

A

C3H8O3

180
Q

In a water treatment plant, explain how charged polymers can be used in the purification process.

A

In a water treatment plant, flocculation is an important step in the purification process because it helps remove suspended particles and impurities from water. During flocculation, positively charged polymers are added to the solution and attract the negatively charged clay particles. Dispersion forces allow particles to aggregate and form larger clumps, called flocs, which can be easily removed by settling or filtration.

181
Q

Explain how nitrification processes play a role in increasing farm productivity. Provide an example of a potential environmental impact if this process is disrupted.

A
  1. Nitrification converts ammonia, found in animal waste and ammonia and ammonium found in fertilizers into the high soluble nitrate ion, which plants can uptake through their roots. Nitrates are essential nutrients for plant growth and enhance crop productivity. However, if these processes are disrupted, it can lead to environmental issues. For example, excessive use of nitrogen fertilizers without proper management can result in increased nitrate runoff into water bodies. This can lead to eutrophication, where excessive nutrient levels cause algal blooms, depleting oxygen levels in water and negatively impacting aquatic life.
182
Q

Discuss the advantages and disadvantages of photovoltaic cells compared to steam turbines as sources of electricity generation.

A

Photovoltaic cells have several advantages compared to steam turbines as sources of electricity generation. Photovoltaic cells directly convert sunlight into electricity, making them a renewable and clean energy source. They have no moving parts, requiring low maintenance. Photovoltaic cells are modular and scalable, suitable for installations of various sizes. They operate silently, making them suitable for urban environments. However, there are also disadvantages to consider. Photovoltaic cells have intermittent energy production due to their dependence on sunlight, making energy storage necessary for continuous power supply. The initial installation costs can be high, although prices have been decreasing. The efficiency of photovoltaic cells is influenced by factors such as weather conditions and panel orientation.

183
Q

Describe the production process of bioethanol, including the chemical equation involved in the fermentation of glucose and any process used to increase the concentration of the ethanol.

A

Bioethanol is produced through a process called fermentation. In this process, carbohydrates such as glucose, are converted into ethanol and carbon dioxide with yeast as the catalyst, as shown below.

C6H12O6 (aq) → 2C2H5OH(l) + 2CO2 (g) ΔH = -ve kJ/mol
Fractional distillation is used to increased the concentration of the ethanol produced.

184
Q

Explain why incomplete combustion is more likely to occur with longer-chain carbon-based fuels compared to shorter chains. Include the products formed and an impact associated with incomplete combustion.

A

Incomplete combustion is more likely to occur with longer-chain carbon-based fuels compared to shorter chains. As the length of carbon chains increases, the ratio of carbon to oxygen increases, limiting the availability of oxygen to form carbon dioxide.
Larger molecules also have stronger dispersion forces making them less volatile fuel sources (more energy required to break interactions). This reduces the ability to mix effectively with gaseous oxygen during combustion. As a result, only partial oxidation of the fuel occurs, leading to the formation of carbon monoxide (CO) and soot (particulate matter). Incomplete combustion of longer-chain fuels can release higher levels of pollutants, including carbon monoxide, which is toxic and can impair oxygen transport in the bloodstream.

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Chemistry (5 decks)

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