metals Flashcards
Which metals are classes and base metals because they are corroded by air
Ag, Au Hg
how do you convert sulfides to oxides
roast the ore in air. SO2 is produced
what problem doesn roasting cause
air pollution as sulphur dioxide is produced
why cant carbon be used to reduce sulfide ores
CS doesnt exist and CS2 isnt exothermic enough
what is smelting
production of a metal from its ore by chemical reduction
what reducing agent is used in smelting
usually C or CO
describe the conditions needed to smelt copper
1084 degrees in a pottery kiln
Malachite + Charcoal + Fe oxide reflux to remove silica
what is bronze made out of and what other copper alloys are there
Bronze is lead and copper - but these are soft metals
copper and arsenic and tin alloys
what is brass made out of
copper and zinc
how is brass made
heating copper and the zinc ore, the ore is reduced and zinc reacts with copper.
Why cant zinc be smelted
cannot be reduced with C until a temp over 1000 degrees is used but zinc will be vapourised at this temp and is readily oxidised.
decribe the process of Fe smelting
Charcoal and Fe ore. This is done at temps below the mp of iron. Molten slag runs out and CO reduces the ore to solid iron
How can iron be made more malleable
Heating in air to 800 -900 degrees or by pudding ie stirring molten cast iron to remove some of the C.
In a blast furnance what do C and CO2 combine to give
CO which is the reducing agent.
If a line for a particular oxide intersects with one of the oxdiation of carbon, what does this show
At or above this temperature the metal oxide can be reduced by C
when do metals burn
if gibbs is large and negative then this is thermodynamically favourable
what is role of CaCO3 in the blast furnance
CaCO3 —> CaO + CO2
CaO + SiO2 —> CaSiO3
reacts with silicia to form a silica slag
what is wrought iron
Pure iron with a little C
what is pig iron
raw iron straight from the blast furnance
What is Cast iron
contains C and Si, made by melting pig iron
What is steel
alloy of iron and C
how do you make steel
Add C to pure iron. Heat with charcoal for a week
what is crucible steel
wrought iron is heated with charcoal at 1550 degress for up to 3-4 days
what is the bessemer proccess
air is blown on molten pig iron reducing the C content for about half an hour. Fe oxidised to and reacts with impurites to give a slag. C —> CO
what are the basic and acidic condtions in the bessemer process
Acidic - converter lined with silicia clay bricks.
Basic - MgO or dolomite lined and lime added to remove phosphate
what is the basic oxygen process and explain the advantages over this than the bessemer process
oxygen blown into 280 tonnes of molten iron. This is better at removing impurities and is more controlable
How is stainless steel made
contains Cr and Ni. Cr forms a passivating invisible layer fo CrO2 on the surface.
what is sodium and how is it stored
Soft metal and in oil
How is Na produced
electrolysis of NaCl or Mixing it witl CaCl2
Na and Na-Ca alloy at cathode and Chlorine at anode.
why cant K be made in a downs cell via electroylsis
K is too soluable in KCl
Vapourises at temperature of reaction
How is K obtained
Reduce with NaCl and distill K off
How is copper electrofined
At anode there are slabs of unpure Cu and at cathodes are thin sheets of Cu. Electrolyte is CuSO3. At anode Cu2+ produced and at cathode Cu ions reduced to pure Cu
How is Ni purified
Sulfide ore is roasted and reduced with C
How is pure Ni obtained
Crude metal is cast into anodes and NiCl2 and NiSO4 are the electrolyte. Impure Ni dissolves at anode and reappears pure at Cathode.
What is the Mond Nickel process and what problem is there with this process
Ni(CO)4 is a volatile liquid and can be purified by distillation. The compound thermally decomposes to Ni and CO. The nickel complex is extremely toxic.
How can a purified CO be obtained from Fe(CO)5
Distilliation and then this thermally decomposes to Fe and purified CO. This is extremely toxic
what process is rusting
electrochemical and requires Fe, water and oxygen
outline the simple process of rusting
Oxidation of Fe to Fe2+ and then oxidation of Fe2+ to Fe3+which ppt out as a hydrate
How can rusting be stopped
By preveting water from getting on surface eg by coating or oiling the surface.
cover it with a metal that will form a passivating layer eg zinc or tin plating.
Use a sacrificial anode of second metal in electrochemical contact with iron eg Zn or Mg
