C15 Flashcards
What is corrosion caused by?
The chemical reactions between the metals and substances in the environment.
What is rusting?
It is the corrosion of iron.
What is the equation for the rusting of iron?
Iron + oxygen + water = hydrated iron oxide
How can rust be prevented?
Air and water needs to be kept away, so by means of oil, grease, plastic and paint. You can also use a more or less reactive metal.
What does it mean when iron is galvanised?
When you use a more reactive metal to coat iron. Therefore zinc is more likely to give away electrons, to form an ion becoming oxidised. Therefore any water or oxygen reacts with the zinc instead of the iron, which is called sacrificial proteciton.
When is sacrificial protection used?
When a coating is likely to be scratched so it protects even when scratched.
What is steel?
It is an alloy of many different metals and elements.
How are carbon steels made?
Made by removing most of the carbon from the iron obtained from a blast furnace. Cheapest steel to make.
What are stainless steels?
They are chromium-nickel steels which combine hardness and strength with good resistance to corrosion. They do not rust.
What is the difference between high carbon steels and low carbon steels?
High carbon steels are very strong but brittle but low carbon steel is soft and easily shaped. It is less likely to shatter though.
What do the properties of a polymer depend on?
The monomers used to make it and the conditions chosen to carry out the polymerisation reaction in.
How is low density polyethene made?
By using very high pressures and a trace of oxygen, ethene forms it.
What are characteristics of low density polyethene?
The polymer chains are randomly branched and cannot pack closely together, hence the low density.
How is high density polyethene made?
Through using a catalyst at 50 degree Celsius and a slightly raised pressure, ethene makes it.
What are characteristics of low density polyethene?
They are closely packed together, and made of straight polyethene chains. It has a higher softening temperature and is stronger.
What are thermosoftening polymers?
They are made of individual polymer chains that are tangled together. They soften easily when heated and reset when they cool down.
What are thermosetting polymers?
They do not melt when heated. They have strong covalent bonds forming ‘cross links’ between their polymer chains.
What are the forces like between thermosoftening polymers?
They are weak and when heated the weak intermolecular forces break, making it soft. When it cools down they come back together and it hardens again.
What are forces between thermosetting polymers like?
Their monomers make covalent bonds between the polymer chains when first heated in order to shape them. Therefore the covalent bonds inbetween chains do not allow them to separate even if heated. It will char at high temperatures.
What is sand made of?
Sand, limestone and sodium bicarbonate.
How is glass made?
They heat the raw materials to 1500 degrees, where they melt it and react them to from molten glass. As it cools it turns into a solid but the particles do not form a regular pattern but a disorderly structure.
How are ceramics made?
Moulding wet clay into desired shapes then heating them to around 1000 degrees.
How is clay arranged?
It is made of compounds of metals and non-metals with ionic bonding between ions, but also has some covalent bonding between non-metal atoms. They are arranged in giant structures which form layers.
What happens to clay once fired in a furnace?
The water is fired out and strong bonds form between the layers, making it harder ceramic.
What are composites?
They are made of two materials, making a product with desired properties for a particular use. e.g. fibre glass and concrete
What do fertilisers need in them?
They need nitrogen to let plants make proteins.
What is the principle of the Haber process?
It is a way of turning nitrogen in the air into ammonia.
Why is ammonia so important?
Due to being used to make other products such as fertilisers.
What are the raw materials for the production of ammonia?
Nitrogen from the air and hydrogen mainly from natural gas.
What is the process of the Haber process?
The nitrogen and hydrogen are purified, then passed over an iron catalyst at a high temperature and pressure. This forms ammonia.
Why is it key the Haber process is reversible?
As the ammonia gas produced breaks down again into nitrogen and hydrogen.
Once the ammonia is produced what happens?
It is removed by cooling the gases so that the ammonia liquefies. It is the separated from the unreacted nitrogen and hydrogen gas. These unreacted gases are then recycled back into the reaction mixture where they are recompressed and heated returning to react again on the surface of the iron catalyst.
What is key about the Haber processes reaction vessel?
It must contain an iron catalyst.
How is the nitrogen extracted for the Haber process?
It is extracted from the air. It is done by fractional distillation of liquid air. It cools it down which needs energy as air needs to be compressed by high pressure pumps
What is the equation for the Haber process?
N2(g) + 3H2(g) = 2NH3(g)
What is the influence of pressure upon the Haber process?
Increase in pressure will shift equilibrium to the right, producing more ammonia. Therefore high pressures produce the most ammonia.
What is the effect of temperature on the Haber process?
The forward reaction is exothermic so lowering the temperature would increase the amount of ammonia in the reaction mixture at equilibrium.
What is the problem of low temperatures in the Haber process?
The rate of reaction would be very slow as gas molecules would collide less frequently. It would also reduce the effectivity of the iron catalyst.
What is the effect of a catalyst on the Haber process?
It would speed up both the rate of the forwards and backwards position by the same amount, not affecting the yield but making it be produced quicker.
How is ammonia used to make a fertiliser?
It is either used in liquid form or added to nitric acid to make ammonium nitrate which is a fertiliser.
What fertiliser can ammonia (alkali) make by reacting with different acids.
Ammonium nitrate, ammonium sulphate and ammonium phosphate
What is the reaction between ammonia and acids?
A neutralisation.
What does NPK stand for in fertilisers?
Nitrogen, phosphorous and potassium.
What actually are NPK fertilisers and why?
They contain formulations of compounds to provide all 3 letters, as no compound containing all three elements has yet been made for use as a fertiliser.
Where does the phosphorous come from?
Deposits of rock containing phosphorous which are mined. It is treated with acids.
Where does the potassium come from?
From potassium salts mined from the ground for use as fertilisers.
Where does the nitrogen come from?
The ammonia made by the Haber process.
