C15 - Using our resources Flashcards
What is corrosion?
the destruction of materials through chemical reactions with other substances in the environment
Describe a specific example of corrosion:
rusting
-only for iron
-needs both air (oxygen) and water to occur
Rust is just hydrated iron oxide which is formed when it reacts with oxygen in the presence of water, which catalyses the reaction
What will happen to this nail?
does not rust, because stainless steel is resistant to corrosion
How can corrosion be prevented?
-physical barrier coating (eg greasing, painting, or electroplating)
-sacrificial coatings (attaching a more reactive metal so it gets corroded instead of the main metal, for example galvanising a metal using a zinc coating)
Galvanising also acts as a physical barrier
Electroplating is using electrolysis to coat objects with a thin layer of metal
What stops aluminium corroding further?
has an aluminium oxide outer layer that protects the inner metal
Say that it is an aluminium oxide layer, not just an oxide layer
Name 4 common alloys and their components:
-bronze (copper and tin)
-brass (copper and zinc)
-gold (usually mixed with silver/copper/zinc, where proportion of gold is measured in carats, with 24 being 100% gold)
-steel (iron with specific amounts of carbon)
Describe the properties and uses of the different types of steel and aluminium alloys you can have:
high carbon - strong but brittle (tools/drill bits)
low carbon - soft and malleable (wires)
stainless - hard and resistant to corrosion (contains nickel and chromium, used for cutlery)
aluminium alloys - low density and resistant to corrosion (planes)
Name and describe 2 types of glass:
soda-lime - made by heating sand, sodium carbonate, and limestone (calcium carbonate)
borosilicate - made from sand and boron trioxide, and has a higher melting point than soda-lime glass
Soda-lime glass is used more commonly
Give 2 examples of ceramics, and describe how they are both made:
-pottery and bricks
-shaping wet clay and heating them in a furnace
What does the properties of a polymer depend on?
Don’t mention intermolecular forces here
-the monomers they are made from
-the conditions they were made under (eg low density and high density polyethene are both produced from an ethene monomer, but have different properties)
Describe the properties and structures of the 2 types of polymers:
thermosoftening - melts when reheated (weak IM forces between polymer chains)
thermosetting -doesn’t melt when reheated (has cross-links of strong covalent bonds between polymer chains)
Thermosetting polymers just burn when heated
Why might a polymer melt when reheated?
-the polymer is thermosoftening
-because it has no cross-links, and its IM forces are weak
What is a composite material? Describe its structure:
-a substance made from 2 materials:
reinforcement - fragments/fibres of material
matrix/binder - material that surrounds the reinforcement
The composition of the 2 materials makes the resulting material stronger
Give 2 examples of composite materials:
-carbon fibre
-fibreglass
What does the Haber process manufacture? What is the product used for?
-used to produce ammonia from nitrogen and hydrogen
-ammonia is used in nitrogen-based fertilisers
Where are the raw materials for the Haber process sourced from?
nitrogen - fractionally distilled from liquid air
hydrogen - react methane (from natural gas) with steam (water vapour)
Explain how the Haber process is used to manufacture ammonia:
-purified N2 + H2 are passed over an iron catalyst at 450°C, 200 atm.
-some of the reactants react to form NH3 in an exothermic reaction
-the reaction is reversible so some of the NH3 produced breaks down back into N2 + H2
-the mixture is then cooled so the NH3 condenses into a liquid and gets separated, and the still-gaseous N2 + H2 is recycled back into the reaction vessel
Why are the conditions for the Haber process not always ideal in terms of equilibrium yield?
it is a compromise between high equilibrium yield, high rate of reaction, and low cost
Why is a temperature of 450°C used for the Haber process?
-increases rate of reaction
-we don’t go higher because it is too expensive
-however the forward reaction is exothermic, so it is a compromise
Why is a pressure of 200atm used for the Haber process?
-there are fewer moles of gas on the product’s side, so it increases yield of NH3 (and also rate of reaction)
-however it is not increased further as it is very expensive to do so due to the strong containment vessels needed to withstand the pressure
A pump is used to increase the pressure to 200atm
What are NPK fertilisers and why are they used?
-a formulation of several different soluble nitrogen, phosphorus and potassium compounds that are put onto plants to supply them with mineral ions
-improves agricultural productivity by encouraging growth
The compounds must be soluble otherwise the plant’s roots would have no way of absorbing the ions used for growth
How are the ingredients for a fertiliser sourced?
-some substances can be mined straight from the ground and added (eg potassium chloride/sulfate)
-others need to be processed first (eg phosphate rock)
How is phosphate rock/ammonia treated to be put in an NPK fertiliser?
treated with nitric/sulfuric/phosphoric acid to produce soluble salts
What can ammonia be used to manufacture?
ammonium salts and nitric acid
Compare the production of fertilisers industrially and in the lab:
-industrial is larger scale
-industrial produces larger quantities faster
-industrial can do it continuously but lab can only do it once in a batch
-industry uses stainless steel apparatus but the lab uses glass (steel is much stronger, can use higher temp/pressures)
What is formed when phosphate rock reacts with nitric acid?
phosphoric acid and calcium nitrate
When asked a question such as “what soluble salt is produced when x reacts with y”, don’t say phosphoric acid because it is unsurprisingly, not a soluble salt.
What is formed when phosphate rock reacts with sulfuric acid?
calcium sulfate and calcium phosphate
This mixture is known as single superphosphate
What is formed when phosphate rock reacts with phosphoric acid?
calcium triple superphosphate
Why might this information be useful to farmers on a bag of a fertiliser?
-shows that it is a formulation, as it gives the proportions of the different N/P/K compounds in it
-this means that the farmer can choose the fertiliser with the required properties/proportions
Why might ammonium nitrate help other substances to burn?
provides oxygen to burn
Why might a different reaction not work with a certain type of catalyst?
different reactions require different catalysts
