C15 Using our Resources
- Created by: Lucy Hart
- Created on: 13-02-20 17:02
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- C15 Using our Resources
- C15.1 Rusting
- corrosion - caused by chemical reactions between metal + substances in the environment
- iron rusts
- aluminium forms protective oxide layer
- both water + air needed
- iron + oxygen + water -> hydrated iron oxide
- preventing rusting
- barrier - paint, grease + plastic
- electroplating - less reactive metal
- sacrificial protection
- iron is galvanised, zinc is more reactive than iron so stronger tendency to form positive ions by giving away electrons becoming oxidised
- C15.4 Glass, ceramics + composites
- glass
- soda lime glass - sand (SiO2), limestone (CaCO3), sodium carbonate (NaCO3)
- borosilicate glass - boron trioxide (B2O3)
- disorderly structure
- heated at 1500C + react to form molten glass
- ceramics
- pottery + bricks
- moulding wet clay heat in furnace around 1000C
- water driven out + strong bonds form between layers in giant structure, changing properties dramatically
- clay contains compounds non metal + metal with ionic bonding
- composites
- two materials - 1 a binder supporting + binding together with fibres + fragments - called reinforcement
- fibreglass
- tough, flexible, waterproof, low density
- advanced composites - carbon fibres + carbon nanotubes instead of glass fibres
- plywood + concrete
- two materials - 1 a binder supporting + binding together with fibres + fragments - called reinforcement
- glass
- C15.3 Properties of Polymers
- monomers join together
- different reaction conditions cause different poly(ethene)
- (HD) high density - catalyst + 50C + slightly raised pressure
- straighter chains + pack more closely
- stronger than LD
- (LD) low density - high pressures + trace of oxygen
- randomly branched together + cannot pack closely
- (HD) high density - catalyst + 50C + slightly raised pressure
- thermosoftening polymers
- individual chains tangled together
- melt easily when heated becuase of weak intermolecular forces
- individual chains tangled together
- thermosetting polymers
- covalent bonds forming cross links
- will not soften or melt easily because of cross linking
- covalent bonds forming cross links
- C15.2 Useful Alloys
- alloy - differently sized metal ions, harder for layers to slip
- copper alloys
- bronze
- statues + decorative items
- brass - alloying copper with zinc
- musical instruments
- bronze
- aluminium alloys
- gold alloys
- pure gold wears away more easily than pure copper
- purity of gold expressed in carats
- steels - iron, carbon + other elements
- stainless steel - great resistance to corrosion + used in reaction vessels
- high carbon steels - hard but brittle
- low carbon steels - soft + easily shaped
- C15.5 Making Ammonia - Haber process
- ammonia used for fertilisers
- raw materials - nitrogen (from air) + hydrogen (natural gas + methane)
- nitrogen + hydrogen -> ammonia
- N2 +3H2 -> 2NH3
- Haber process
- 1. hydrogen + nitrogen pumped in
- 2. compressed to pressure 200 atm + 400C
- 3. added to iron catalyst in reaction vessel
- 4. reactor cools and mixture liquifies
- 5. unreacted hydrogen + nitrogen recycled
- 4. reactor cools and mixture liquifies
- 3. added to iron catalyst in reaction vessel
- 2. compressed to pressure 200 atm + 400C
- 1. hydrogen + nitrogen pumped in
- C15.6 economics of Haber process
- effect of pressure
- N2 + 3H2 -> 2NH3
- 4 molecules of gas on reactants + 2 molecules on products
- volume of reactants is greater so shift to products side (pressure favours less moles, more space)
- high pressure needed for best yield but expensive so 200 atm
- 4 molecules of gas on reactants + 2 molecules on products
- N2 + 3H2 -> 2NH3
- effect of temperature
- lowering temperature would increase amount of ammonia becuase exothermic
- higher temperature increases yield so compromise
- effect of catalyst
- iron catalyst speeds rate of reaction but not yield of ammonia
- effect of pressure
- C15.7 Making Fertilisers in the Lab
- fertiliser - a substance that contains nutrients to help another substance grow
- mad by titration - neutralisation
- ammonia + nitric acid -> ammonium nitrate
- NH3 + HNO3 -> NH4NO3
- ammonia + phosphoric acid -> ammonium phosphate
- 3NH3 + H3PO4 -> (NH4)3PO4
- ammonia + sulfuric acid ->. ammonium sulfate
- 2NH3 + H2SO4 -> (NH4)2SO4
- NPK fertilisers
- formulations of various salts containing appropriate percentages of elements
- contain all 3 compounds
- C15.8 Making Fertilisers in Industry
- nitrogen (nitric acid) comes from ammonia made from Haber process
- phosphorus from phosphate rock
- potassium comes from potassium salts mined
- C15.1 Rusting
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