C6.1 Flashcards
what is acid mine drainage?
mines that flood when they are abandoned
how does acid mine drainage occur?
reactions occur between metal sulfides and other metal ores, these reactions happen naturally but certain bacteria make them go faster
bioleaching
biological method of metal extraction in which bacteria speed up reactions that release soluble metal compounds from metal sulfides
advantages of bioleaching
-cheaper than traditional mining
-allows metals to be extracted from ores that contain too little metal for traditional methods to be profitable
-bacteria occurs naturally and don’t need any special treatment
-doesn’t release harmful sulfur dioxide
disadvantages of bioleaching
-slow process
-can produce toxic substances
-lots of care needs to be taken to avoid toxic chemicals escaping into water supplies and soil
phytoextraction
biological method of metal extraction in which plants absorb metals through their roots and concentrate them in their cells
advantages of phytoextraction
-cheaper than traditional mining
-produces less waste
-involves smaller energy transfer
-closer to being a carbon neutral activity
-absorbs CO2 for photosynthesis when they grow
disadvantages of phytoextraction
-slow process
-crops may need replanting for years before available metal is removed from the soil
-releases CO2
what is the reactivity series?
- Potassium
2.Sodium
3.Lithium
4.Calcium
5.Magnesium
6.Aluminium
7.Zinc
8.Iron
9.Lead
10.Copper
11.Silver
12.Gold
13.Platinum
where does carbon fit on the reactivity scale?
in between aluminium and zinc
what is the method of extraction for the top 6 elements in the reactivity scale?
electrolysis of molten ores
what is the method of extraction for the middle four elements of the reactivity scale?
reduction of ores using carbon
what is the method of extraction for the bottom three elements in the reactivity series?
metals occur uncombined- mine directly out of ground
what is an ore?
a rock or mineral that contains enough metal to make it economical to extract the metal (the value of the metal is more than the cost of extracting it)
what does malachite contain?
copper carbonate
what does bauxite contain?
aluminium oxide
what does haematite contain?
iron (III) oxide
how does extracting metals by heating with carbon work?
-any metal below carbon on the reactivity series can be extracted from its metal compound by heating with carbon or carbon monoxide- this is an example of a redox reaction
-the metal oxide loses oxygen, it is reduced, this forms a metal
-the carbon/carbon monoxide gains oxygen, it is oxidised, this forms carbon dioxide, the carbon/ carbon monoxide is acting as the reducing agent
what is oxidation in terms of oxygen?
gain of oxygen
what is reduction in terms of oxygen?
loss of oxygen
what factors might be considered before a metal ore is mined?
if there is enough metal in the rock to make it economical to extract it
why can carbon be used to extract metals such as copper and iron from their ore?
carbon is more reactive than copper and iron so a displacement reaction takes place and the metal becomes reduced
why can’t carbon be used to extract metals such as aluminium?
aluminium is more reactive than carbon so no displacement reaction takes place
what does aluminium naturally exist as?
aluminium oxide (Al2O3)
where is aluminium oxide found?
in the ore called bauxite
what is aluminium used for?
making aircrafts, cooking foils and drinks cans
what products will form when aluminium oxide goes through the process of electrolysis?
aluminium and oxygen
what are some problems with extracting aluminium and why?
aluminium has a melting point of 2072°C and is insoluble- this is a problem because it requires a lot of money and energy to maintain
what is done to overcome this problem of aluminium?
dissolve the aluminium oxide into molten cryolite, melting point of cryolite is 950°C (this is still high but’s less expensive)
what is crude oil?
-crude oil is a mixture of hydrocarbon molecules of different sizes
-it’s a finite, non-renewable resource because it is being used up faster than it is being formed
how can crude oil be made useful?
-as a mixture, crude oil is not very useful
-it is much more useful to separate the hydrocarbon molecules into fractions according to their size
describe how fractional distillation is used to separate crude oil (4 marks)
- Oil is heated and pumped into the bottom of a tall tower called a fractioning column, where it vaporises
- The column is very hot at the bottom but much cooler at the top. As the vaporised oil rises, it cools and condenses
- Heavy fractions which have stronger intermolecular forces and higher boiling points condense near the bottom of the column
- Lighter fractions which have weaker intermolecular forces and lower boiling points condense further up the column
distillation
method which separates mixtures based on different boiling points
simple distillation
separates a solvent from a solution, leaving the solute behind
fractional distillation
separates mixtures of liquids
what does it mean when the molecules are longer (have more C atoms)?
they have stronger intermolecular forces, requiring more energy to break apart, leading to a higher boiling point
what does it mean when the molecules are smaller (have fewer C atoms)?
they have weaker intermolecular forces, requiring less energy to break them apart, leading to a lower boiling point
what enters the bottom of a fractional distillation column?
bitumen
what leaves the top of a fractional distillation column?
LPG
what are the bonds like in Alkanes?
single bonds
what are the names of some Alkanes?
-Methane
-Ethane
-Propane
-Butane
-Pentane
what is the general formula for Alkanes?
Cn H2n+2
what are the bonds like in Alkenes?
must contain a double bond
what are the names of some Alkenes?
-Ethene
-Propene
-Butene
-Pentene
what is the general formula for Alkenes?
Cn H2n
why are smaller hydrocarbons more useful as fuels?
they are more volatile and easy to ignite
why is there a very high demand for small chain hydrocarbons?
we use them as fuel in our everyday life e.g. petrol
which fractions of crude oil are produced the most in fractional distillation?
long chain molecules
describe the process of cracking
when you take a long hydrocarbon and brake into two, it starts as an alkane and when broken in two it becomes an alkene and an alkane
as well as for fuels, what else can smaller hydrocarbons be used for?
the manufacture of plastics
describe the two ways in which cracking can be carried out
- thermal cracking (high temperature and pressure)
- catalytic cracking (low temperature and pressure- catalyst)
why is catalytic cracking the preferred method used in industry?
saves energy and money
why may the weather effect phytoextraction?
Phytoextraction is completely dependant on the growing and harvesting of crops, for the crops to grow they need enough sunlight and water. This is why the weather will affect it as it controls conditions.
potable water
water that is safe to drink
what is aluminium mixed with before electrolysis and why?
cryolite as it lowers its melting point
what is the atmosphere?
a relatively thin layer of gases which surround the earth
what is the atmosphere made up of?
-nitrogen
-oxygen
-argon
-carbon dioxide
-water vapour
what percentage of the atmosphere is made up of nitrogen?
78%
what percentage of the atmosphere is made up of oxygen?
21%
what percentage of the atmosphere is made up of argon?
1%
what percentage of the atmosphere is made up of carbon dioxide?
0.004%
what percentage of the atmosphere is made up of water vapour?
variable
what is the relationship between the length of the carbon chain and the supply and demand?
-smaller fractions: demand outweighs the supply
-larger fractions: supply out ways the demand
explain how cracking could help satisfy the demand for fuels
For smaller fractions the demand outweighs the supply. Cracking helps satisfy the demand as the larger fractions, in plentiful supply, are broken down into smaller more useful hydrocarbons (alkanes/alkenes)
around 90% of crude oil is used for fuels, what could the other 10% be used for?
-lubricating oils
-roads and roofing
-plastics/polymers
