Getting Metals From Ores Most metals do not occur naturally (native).They have to be extracted from metal containing rocks (ores.) • First substances other than the metal compound are removed (concentration.) • Next the metal itself is extracted from its compound (reduction).
The more vigorously an element forms compounds the harder it will be to get back that element from its compounds. Eg. Magnesium gives out lots of heat when it combines with oxygen. This means we will have to put lots of energy back to extract magnesium from magnesium oxide. I.e. It will be hard to extract. Extraction of Metals and Energy Changes
Extraction Processes The reactivity of a metal Determines the method of extraction. The Reactivity Series potassium Increasing reactivity sodium Metals above carbon must be extracted using electrolysis. calcium magnesium aluminium (carbon) zinc Metals below carbon can be extracted from the ore by reduction using carbon, coke, or charcoal. iron lead copper silver Gold and silver often do not need to be extracted. They occur native. gold
Here is a list of the symbols of some mostly less common metals in order of decreasing reactivity. Use this to assign the most likely method of extraction: native (N), carbon(C), electrolysis (E). Li, Ce, Mn, Al, Zn, Cd, Sn, Pb, Cu, Pd, Activity Extracting Methods Symbol Li Zn Mn Ce Pd Cu Al Cd Sn Method (N, C or E)
Because gold occurs native its extraction is a low-tech affair that simply involves finding it! Extracting Gold
Iron is a moderately reactive metal. Iron ore is plentiful and relatively easily reduced to iron metal by heating with coal (carbon). It is therefore cheap. It is strong and malleable (non-brittle). Iron is the most commonly used metal. Iron
Reactions - Reduction of Iron Ore carbon + oxygen carbon dioxide C(s) + O2(g) CO2(g) Carbon dioxide + carbon carbon monoxide CO2(g) + C(s) 2CO(g) Carbon monoxide + iron oxide iron + carbon dioxide 3CO(g) + Fe2O3(s) 2Fe(s) + 3CO2(g)
Reactions – Removing Impurities Calcium carbonate calcium oxide + carbon dioxide CaCO3(s) CaO(s) + CO2(g) Calcium oxide + silicon dioxide calcium silicate CaO(s) + SiO2(s) CaSiO3(s) This is called SLAG
Activity Extraction of Iron
Copper is a metal of low reactivity. It occasionally occurs native but more often occurs as copper compounds. Heating copper compounds with carbon gives copper but this is not pure enough to use for electrical work. Copper
The conductivity of copper is drastically reduced by tiny amounts of impurities. Because of this most copper metal is further purified by electrolysis. In this process impure anodes dissolve. This dissolved copper is plated onto a cathode leaving behind impurities. Electrolytic Purification
Opposite charges attract. And so positive copper ions Cu2+ move to the negative cathode. At the cathode these ions gain electrons and turn into copper atoms. So, in electrolysis a copper cathode gets thicker and thicker Copper Atoms at the Cathode
Impure copper is used as the anode of an electrolysis cell. The battery pulls electrons off the copper atoms that the anode is made up from. By losing electrons these atoms change into copper ions and so the anode slowly “dissolves” away. Impurities just sink to the bottom as “anode mud.” Copper Ions Form at the Anode
Purification: The Half Reactions Anode (+ve electrode) Cu(s) Cu2+(aq) + 2e- Cathode (-ve electrode) Cu2+(aq) + 2e- Cu(s)
Copper is purified to improve its NOT CIVIC DUTY Copper is purified by CELERY IS LOST Pure copper forms at the DO TEACH Impurities form called A ODD MENU The anode will slowly DIVE LOSS At the cathode copper ions gain CORN STEEL Activity Unscramble the words to end the sentences conductivity electrolysis cathode anode mud dissolve electrons
Platinum is a rare and expensive metal used in jewellery and also for plating the fuel nozzles in jet engines. It was first discovered by Europeans in 1735 but in South America the primitive pre-Columbian Indians had been using it for centuries. Activity Extracting Platinum Approximately where would you place platinum in the activity series? In what form do you think platinum occurs?
Copper is purified using electrolysis. Plan an experiment to investigate factors that might affect the rate of copper production. Include: Any factors that might affect rate. The apparatus you would need. A statement of how you would control variable in an investigation. The number and range of readings. The safety issues you would take into account. Activity Purifying copper and electricity
Some factors that might affect rate. Concentration of solution. Distance apart of electrodes Electrical potential (volts) or current (amps). Duration of electrolysis. A Purifying copper: some answers (1) Apparatus 3.3g
Control of variables. Basically only change one variable at a time! Number and range of readings Minimum of 8-10 different values Repeat readings at least once Attempt a range providing 10-fold change. Safety Issues Check electrical, toxicity, corrosive etc. Take appropriate measures Purifying copper: some answers (2)
Aluminium is a reactive metal. We might expect it to corrode easily but a strong coating of oxide on it’s surface prevents this in most everyday situations. It has a low density which leads to its extensive use in the aerospace industry. Coating of oxygen atoms prevents further attack O O O O O O O O O Al Al Al Al Al Al Al Al Al Al Al Al Aluminium: Properties
It occurs as bauxite ore which is a form of aluminium oxide. Because aluminium is so reactive carbon is unable to pull away the oxygen from it. It is extracted by electrolysis of molten bauxite. Early attempts at this failed because bauxite is so hard to melt. If cryolite is added the bauxite melts more easily. This is an essential step in the extraction process. Aluminium: Ores
Graphite (carbon) anodes Molten electrolyte bauxite + cryolite Electrolytic extraction A bauxite / cryolite mixture is melted in a steel container containing a carbon lining. Graphite anodes are inserted into the molten electrolyte ready for electrolysis. Tank lined with carbon cathode Steel case
Opposite charges attract. And so positive aluminium ions move towards the negative cathode. At the cathode these ions gain electrons and turn into aluminium atoms. Aluminium Formation
Negatively charged oxide ions move to the anode. Here they lose 2 electrons and so turn into neutral oxygen atoms. These atoms rapidly join into pairs to form normal oxygen gas. Oxygen formation
Remember the electrolysis is carried out at high temperature. Under these conditions quite a lot of the oxygen reacts with the carbon anode. Carbon dioxide is formed and the anode is rapidly eaten away and frequently has to be replaced. Carbon Dioxide Formation
Extraction of aluminium: overall Vented cover siphon Molten aluminium out Graphite / carbon anodes Tank lined with carbon cathode Steel case Molten electrolyte bauxite + cryolite Molten aluminium
Extraction of aluminium using electrolysis - half reactions Anode (+ electrode) 2O2-(l) O2(g) + 4e- Cathode (- electrode) Al3+(l) + 3e- Al(l) Overall 2Al2O3(l) 4Al(l) + 3O2(g) The anode reacts to form carbon dioxide C + O2 CO2
Common aluminium ore I axe tub Added to reduce melting point City role The electrodes are made out of Right ape Extracting aluminium is a Cretin duo Activity Unscramble the words to end the sentences bauxite cryolite graphite reduction
Activity Aluminium – the Overall Process
Since the war of 2042 world trade had been drastically reduced. Many countries have a policy of using home produced materials wherever possible because imported materials remain difficult to buy. A Rotten Week in the State of Chemark The country of Chemark had done relatively well at using its own resources but supplies, even of home produced materials, can be unreliable.
The major town of Chemsville, in the state of Chemark, has 2 main industries: -ChemCars – manufacturing expensive cars -ChemComm – engaged in communications products such as newspapers, books, CDs and DVDs It also had an 80% completed aircraft factory: ChemJet -ChemJet has orders for 22 executive jets which they are committed to delivering to a tight schedule. There are also several large farms within the borders of Chemsville producing crops and meat. Chemsville
The week starts badly! The company that electrolyses salt in Chemark has had a major fire. The ElectroSalt factory will not open again for at least 3 months. The mayor of Chemsville phones. She urgently wants you to produce a brief report setting out: What rock salt is used for? How the factory close-down may affect companies, farmers and non-industrial activities in Chemsville Monday – Fire at ElectroSalt 1 Draw up this report for the mayor. Include diagrams / flow charts of products from salt and suggest problems that the absence of these may cause for Chemsville companies.
Some answers for the mayor! p.v.c. chlorine Manufacture of Aluminium Water treatment Sodium hydroxide Manufacture of paper Paper bleaching Manufacture of textiles hydrogen pesticides Monday: Useful products from Rocksalt Salt
Monday: Answers about Rocksalt ChemCar & ChemJet Plastic shortages due to lack of chlorine. (Needed for wire insulation and plastic components.) Textiles shortages (for seat covers etc) due to lack of sodium hydroxide. Aluminium shortage due to shortage of sodium hydroxide. Major problem for ChemCar and dire problem for ChemJet
Monday: Answers about Rocksalt ChemCom Paper shortages due to lack of chlorine and sodium hydroxide Plastic shortage needed to make CDs and DVDs
Monday: Useful products from Rocksalt Farmers Shortage of insecticide. Others Lack of chlorine for water treatment – health risks if untreated water
ElectroSalt had been one of the major customers of the only Electricity company. Loss of ElectroSalt’s custom has taken ElectroGen into financial problems and they announce an emergency price rise of 50% for electricity. The mayor phones. What effect will this have upon the cost of products made in Chemsville? Wednesday: Price Rises by ElectroGen Draw up a report for the mayor. What materials used in existing factories and in the new aircraft factory may involve major quantities of electricity? Can it’s use be avoided?
Obviously there are normal running costs in all of the organisations but two vital products will be hit by the price rise and are difficult to get replace. Copper – for wiring of cars and aircraft. (Copper is refined by electrolysis which uses large amounts of electrical power.) Aluminium – for use in cars and especially in aircraft. (Aluminium is extracted by electrolysis of molten bauxite.) Wednesday: Report about ElectroGen
It seemed things could only get better - wrong! The director of the unfinished aircraft factory phones saying the company providing cement has been unable to get supplies because of a strike at the limestone quarry. The aircraft factory must be finished on time. The director suggests using an old limestone wall and clay from the foundations of the new factory to make enough cement to finish the factory off. Is this feasible / sensible? Friday: Limestone shortage Make recommendations on how to get the cement. Who else in Chemsville may be affected by a limestone shortage?
The limestone wall could be heated to produce calcium oxide and this could be mixed with clay to make cement so this could solve the problem. It might make more sense to ship the limestone to the existing cement factory to make a batch of cement as they already have the necessary equipment. This is my recommendation. Limestone Cement Clay Friday: Answers to Limestone shortage
The building of the ChemJet factory is not the only thing that will be affected by a limestone shortage. The strike will affect manufacture of iron from which steel is made. This could have major effects on ChemCar as many car components are made of steel. In the longer term it will also affect farmers who use limestone to neutralise their soil. Friday: Answers to Limestone shortage
Which of the following metals is most likely to occur native? Sodium Zinc Iron Gold
Which of the following metals has to be extracted by electrolysis? Sodium Zinc Iron Gold
Which of these happens in the purification of copper? Copper cathode dissolves Copper anode gets thicker Copper atoms become ions at the cathode Copper ions become atoms by gaining electrons.
Which of these happens in the extraction of iron? Carbon oxidises the iron oxide Combustion of carbon provides the energy for the extraction process. Carbon monoxide reacts with acidic impurities in the iron ore. The waste gas is mainly carbon monoxide