Blast Furnace and Extractions Flashcards
Extracting metals that are above carbon in the reactivity series
Must be extracted using electrolysis
Extracting metals that are below carbon in the reactivity series
Can be made from their ores by heating them with carbon
Main ore of Aluminium
Bauxite - Clay mineral, impure aluminium oxide
How is the problem of aluminium’s high temperature solved?
Aluminium oxide dissolved in molten cryolite (a solent)
Decreases required operating temperature
Ionic half equation at anode in aluminium extraction
Oxide ion lose electrons to form oxygen gas
2O 2- –> O2 + 4e-
Ionic half equation at the cathode in aluminium extraction
Aluminium ions reduced to aluminium by gaining electrons
Al 3+ + 3e- –> Al
Aluminium extraction, why do the positive electrodes need to be replaced
Because of the high temperatures, carbon anode burn in oxygen to form carbon dioxide
Major cost of aluminium extraction
Lots of electricity needed to make solution molten, due to its high melting point
Uses and properties of Aluminium (3)
Aluminium alloys normally used (not very strong)
Pots & pans-shiny, resists corrosion, low density, good conductor of heat
Overhead cables-Resists corrosion, low density, good conductor of electricity
Conditions needed for the extraction
Catalyst
Temperature
Catalyst - Cryolite
Temperature - 1000 degrees
How is pig iron made
Molten iron straight from furnace is cooled rapidly & solidified by running it through sand moulds
How is cast iron made
Pig iron is remelted & cooled under controlled condition (very impure iron)
Uses and properties of cast Iron
Castings - Very fluid when molten, doesn’t sjrink when solidified
Very hard but brittle
Man hole covers, guttering and drainpipes
Iron ore
Haematite
Fe2O3
Blast furnace:
Trends of boiling point and viscosity of main fractions
Further down column, molecules:
Are larger
Have higher boiling points
Are more viscous (flow less easily
Blast Furnace: CO2 +C –> 2CO
High temperature
Carbon dioxide reduced by carbon to give monoxide
Blast Furnace C + O2 –> CO2
Coke is impure carbon
Burns in hot air blast to form carbon dioxide
Strongly exothermic
Blast Furnace: Fe2O3 + 3CO –> 2Fe + 3CO2
Carbon monoxide, main reducing agent-iron oxide
Iron melts & flows to bottom of the furnace, tapped
Blast furnace: Fe2O3 + 3C –> 2Fe + 3CO
In hotter parts of furnace
Some iron oxide also reduced by carbon
Carbon monoxide, not dioxide, made at these temperatures
Blast furnace: CaCO3 –> CaO + CO2
Limestone added to furnace
Removes impurities
Limestone undergoes thermal decomposition
Endothermic - if too much limestone added furnace is cooled
Blast furnace: CaO + SiO2 –> CaSiO3
To remove impurities
Reacts with silicon dioxide to make calcium silicate
Trickles to bottom of furnace as molten slag, which floats on top of molten iron & can be tapped off separately
