Global Challenges Flashcards
What is oxidation and reduction in terms of oxygen?
oxidation = gaining oxygen
reduction = losing oxygen
What is the easiest way to separate a metal from its oxide?
react it with carbon to form the metal and carbon dioxide
What can we not use carbon reduction with all metals?
you can only use it with metals that are less reactive than carbon
What other process separates metals from their oxides other than carbon reduction?
electrolysis`
Why do we find pure gold in the ground, but not pure iron?
gold is too unreactive to react with oxygen in the air, but iron is reactive enough and forms iron oxide
What is corrosion?
the process by which metals are slowly broken down by reacting with substances from their environment
What is the equation for rusting?
iron + oxygen + water —> hydrated iron (lll) oxide
what are the conditions required for rusting to take place?
water, iron and oxygen
What type of reaction is rusting?
redox
how can we investigate the conditions required for iron to rust?
set up 3 test tubes with a bung and an iron nail in each.
The first test tube should have water and no oxygen (water should be boiled to remove oxygen and a layer of oil on top to prevent air dissolving into water)
The second test tube should have just the nail and calcium chloride (to remove any water vapour from the air)
the last test tube should have enough water to keep the nail half wat submerged
Why doesn’t aluminium break down as it corrodes like iron does?
The aluminium oxide forms a protective layer, preventing further oxidation
What are the 2 types of methods we can use to protect iron from rusting?
barrier methods and sacrificial methods
What do barrier methods do?
prevent oxygen and water from touching the iron
What do sacrificial methods do?
a more reactive metal is added to the iron, so that metal reacts instead of the iron
what are 3 main barrier methods?
paint
oil or grease
electroplating
What is electroplating?
using electrolysis to cover the iron with a thin layer of another metal
What is an example of protection that uses both barrier and sacrificial methods?
galvanising
What is galvanising?
coating an object in a thin layer of zinc
What is the Haber process?
the industrial production of ammonia from nitrogen and hydrogen
What is the ammonia used for in the Haber process?
to create nitrogen based fertilisers
How does the Haber process work?
1) input the nitrogen and hydrogen into the reacting vessel
2) Some of the nitrogen and hydrogen react to form ammonia
3) The mixture passes into the condenser and the ammonia cools down to liquid ammonia (it has a low boiling point) whilst the hydrogen and nitrogen stay gaseous
4) the liquid ammonia is collected and the nitrogen and hydrogen are recycled
What are the conditions inside the reacting vessel?
450 C
200 atm
iron catalyst
Why does the Haber process take place at 450 C and 200 atm?
as the reaction exothermic, a lower temp. favours the forward reaction and higher % yield, but to achieve a higher rate of reaction, more temp is needed. 450 C is selected as a compromise. A higher temperature is too expensive as well
Higher pressure will increase rate of reaction and push equilibrium to the right, increasing % yield. High pressure is very expensive and can be dangerous, so 200 atm is a compromise
Is the Haber process an exothermic or endothermic reaction?
exothermic
Which metal acts as a catalyst for the Haber process?
iron
Where do we get the nitrogen required for the Haber process from?
take it from the air
Where do we get the hydrogen required for the Haber process from?
make it from hydrocarbons
What is a fertiliser?
a substance that is applied to soil, in order to supply plants with nutrients.
What is a formulation?
a mixture that has been designed as a useful product. e.g. paint, fertiliser etc.
What does NPK stand for in NPK fertilisers?
nitrogen (N), phosphorous (P), potassium (K)
What are the 3 main elements that plant need from soils?
nitrogen, phosphorous and potassium
What is used to provide nitrogen in the fertilisers?
ammonia made from the Haber process
What is the contact process?
the industrial process which produces sulphuric acid
What are the 3 main steps in the contact process?
1) sulphur is combusted with oxygen to form sulphur dioxide
2) Sulphur is further oxidised using vanadium (V) oxide catalyst to form sulphur trioxide
3) the sulphur trioxide is reacted with water to sulphuric acid
What are the 3 main steps in the contact process using equations?
1) S₈ + 8O₂ → 8SO₂
2) 2SO₂ + O₂ ⇄ 2SO₃
3) SO₃ + H₂O → H₂SO₄
What are the optimal conditions for the contact process?
450 C
2 atm
vanadium (V) oxide catalyst
Which factor increases the rate of reaction but decreases the percentage yield in the contact process?
temperature
What is the purpose of a life cycle assessment (LCA)?
To assess the environmental impact of products
What are the stages of a LCA?
extracting and processing the raw materials
manufacturing and packaging the product
using the product
disposing of the product
What are 3 limitations of LCAs?
Companies can manipulate their LCAs to look more favourable
It is difficult to gather all of the required data about each step
It is difficult to compare different harms e.g. lung disease vs global warming
What are some of the characteristics of ceramics?
hard, brittle, heat-resistant, corrosion-resistant
How are ceramics made?
by shaping and then firing a nonmetallic material, such as clay, at a high temperature.
what are the 2 main groups of ceramics?
clay ceramics and glass.
What are 3 clay ceramics and what is a characteristic they share?
brick, china, porcelain
high compressive strength
What is the most common glass we use?
soda-lime glass
How is soda-lime glass made?
melting a mixture of sand (silicon oxide), sodium carbonate and limestone, then allowing the molten liquid to cool and solidify
How is borosilicate glass made?
by heating sand (silicon oxide) with boron trioxide.
what is a difference in soda-lime glass and borosilicate glass/
borosilicate glass has a much higher melting point
What are composites?
A composite material consists of two or more materials with different properties, that have been combined to produce a material with more desirable properties.
What are the 2 components most composite materials are made from?
the reinforcement (long solid fibres or fragments)
the matrix (binds the reinforcements together, often starts soft then hardens)
What are polymers?
large molecules of high relative molecular mass and are made by linking together large numbers of smaller molecules called monomers.
Generally, what properties do polymers have?
flexible, easily shaped, and good insulators of heat and electricity.
What does LDPE stand for?
low-density poly(ethene)
Which type of poly(ethene) is most flexible, but weakest?
LDPE
What does HDPE stand for?
high-density poly(ethene)
Which type of polymers melt easily when heated?
Thermosoftening polymers
What are the 2 types of polymers?
Thermosoftening polymers
thermosetting polymers
What are general characteristics of metals?
malleable, ductile, good conductors of heat and electricity, and have high melting and boiling points
What is the key difference between metals and alloys?
Alloys are not malleable and much stronger
how does fractional distillation work?
Crude oil is a mixture of hydrocarbons with different boiling points.
The first step is to heat the crude oil to a very high temperature so that all of the compounds are evaporated from liquid to gas.
The hot gaseous hydrocarbons then rise up the fractionating column (because hot gas rises).
As they rise, they cool down, because the top of the column is cooler than the bottom.
The hydrocarbons will condense when they become cooler than their boiling point, and the liquid hydrocarbons then collect in trays and drain out.
The longer chain hydrocarbons condense at the bottom of the fractionating column because they have high boiling points.
Meanwhile the shorter chain hydrocarbons condense at the top of the column because they have much lower boiling points.
What 3 hydrocarbons are used as fuels?
Diesel
Petrol
Kerosene
What is a petrochemical?
a substance made from crude oil via chemical reactions.
what is feedstock?
a raw material used to provide reactants for an industrial reaction.
What are alkanes?
a homologous series of molecules that are hydrocarbons and that only have single bonds
What is the general formula for alkanes?
CnH2n+2
What does a homologous series mean?
group of organic compounds that have similar chemical properties, due to them having the same general formula.
What does saturated and unsaturated mean in terms of molecular bonds?
saturated means that only single bonds are present, but unsaturated means that other bonds are also present (e.g. double bonds)
What is the general formula for alkenes?
CnH2n
What is a fuel cell?
a type of electrochemical cell that converts energy between chemical and electrical
In hydrogen fuel cells, which electrode has what charge?
anode - negative
cathode - positive
What are the electrodes made of in fuel cells/
porous carbon with catalyst
How do hydrogen fuel cells work?
1) Hydrogen comes into the anode compartment and gets oxidised by the anode to become H+ ions
2) the electrons pass around the wire to the cathode, whilst the hydrogen ions pass through the electrolyte to the cathode
3) the hydrogen ions, electrons and oxygen (from the cathode compartment, react together to form water.
4) the water leaves the fuel cell through the outlet
What is the reaction happening at the anode?
H2 —-> 2H+ + 2e-
What is the reaction happening at the cathode?
O2 + 4H + 4e- —–> 2H2O
What is the overall reaction in a fuel cell?
O2 + 2H2 —-> 2H2O
What generates electricity?
the oxidised hydrogen atoms, create a potential difference across the electrodes, driving the electrons through the wire to the cathode
What are 3 pros of hydrogen fuel cells?
only require hydrogen and oxygen (abundant)
dont produce waste
relatively simple
last longer than batteries
less polluting to dispose of
