Extraction of Metals from Their Ores Worksheet - Coursework Example

Extraction of Metals from their Ores Worksheet The exercise you are going to complete uses a collection of websites, data tables and charts to lead you through key ideas that you need to in order to understand the relationship between reactivity, price and extraction methods of different metals. You will need to use this template to fill in the tables and answer the questions below. You might find the three websites below useful to refer to. However you must not copy and paste from these websites but write the information in your own words. If I suspect that any information has been copied and pasted I will put it through a program called turnitin and you will lose marks!! http://www.webelements.com http://www.gcsescience.com/periodic-table.htm http://www.gcsescience.com/ex9.htm http://www.docbrown.info/page01/ExIndChem/ExIndChemc.htm#produced Part 1 metals and their ores TASK 1 Complete the following tables. Metal Common ore Formula of ores Information about uses/history/properties Aluminium Bauxite Al2O3.2H2O Used in making cans, foils and alloys for the construction of aeroplanes/Ancient Greek and Romans used alum to make medicines/it is a light, reactive metal Iron Haematite Fe2O3 Used to make steel which is used to make buildings, vehicles, aircrafts etc/Was used even in prehistoric times/it is magnetic, strong conductor of electricity, brittle and resistant to corrosion Lead Galena PbS Used as a shield for radioactive elements, in making different alloys/ Ancient Romans used lead in plumbing/ Poor conductor of electricity, malleable, ductile Zinc Sphalerite ZnS Used to make the alloy brass, to galvanize metals and to make batteries/ before it was recognized as a separate element, it was used to make brass by ancient civilizations/ it is hard, brittle, a fair conductor of electricity and a moderately reactive element Tin Cassiterite SnO2 It is used to plate steel, to make tin cans and an alloy with lead called solder/ it was used back in the Bronze Age to make alloys/ it is malleable, ductile and becomes a superconductor at low temperatures Copper Chalcopyrite CuFeS2 It is used in plumbing and to make electrical wires/it was used even in prehistoric times and was later used to make brass/Very good conductor of electricity, malleable, resistant to corrosion and very unreactive. Gold Native metal, electrum (alloy) - It is used mainly for jewellery and decorative purposes, and also for electrical contacts and electroplating/Used in Ancient civilizations especially Egypt for jewellery and ornaments/it is highly unreactive, malleable and ductile. Titanium Rutile TiO2 Its alloys with other metals are used to make aircrafts and engines/ it was discovered in 1791/ It has a low density, high strength, resistant to corrosion and highly unreactive. (32 marks) 1. Name the two elements that are commonly bonded to metals in their ores. (2 marks) Oxygen and Sulphur. 2. Can you suggest a reason for this? (3 marks) These elements are strong non-metals and are unstable in their elemental state and they can form stable compounds when reacted with the more reactive metals. Furthermore the reactions that form these compounds are exothermic hence they are favoured and oxygen and sulphur are commonly bonded to metals in their ores. TASK 2 The discovery of the metals http://www.webelements.com Finish the following table and use the data to answer the questions below: Metal % by mass in earth’s crust Date of discovery Aluminium 8.1 1825 Iron 5.0 Before 3000 BC Calcium 3.6 1808 Sodium 2.8 1807 Potassium 2.6 1807 Magnesium 2.1 1755 Zinc 0.11 Before 1000 BC Copper 0.001 9000 BC Silver 0.00003 Before 3000 BC Gold Less than 0.000001 Before 3000 BC (10 marks) N.B over 70% of the earth’s crust is made of two elements: oxygen (46%) and silicon (28%). 3. Why do you think that gold is more expensive than iron, aluminium or zinc? (1 mark) Gold is more expensive than all these metals because it is rarer. 4. Referring to the table of reactivity for metals on page 231 of your text book, can you see any relationship between the reactivity of the metals and their date of discovery? Describe any relationship you can see. (4 marks) There is a relationship between the reactivity of elements and their date of discovery; the more reactive elements were discovered later, around the 18th and 19th century, whereas the less reactive elements were discovered at the latest by 1000 BC. More reactive elements such as potassium to magnesium were discovered around the early 19th century, while less reactive elements, starting from zinc to silver were discovered from 1000 BC dating back to as much as 9000 BC. 5. How can we test to see how reactive metals are? Suggest two methods. (2 marks) Method 1: React the metals with cold water, warm water and/or hot water and note the reaction that follows. More reactive metals will react easily with cold water, less reactive metals with react less vigorously with warm water whereas the metals with very low reactivity will not react even with hot water. Method 2: React the metals with dilute hydrochloric acid. The metals that are most reactive will give off hydrogen gas easily, while less reactive metals with displace hydrogen less easily and the metals with least reactivity such as gold and silver will not react at all. TASK 3 Different metals are extracted from their ores in different ways. Useful website: http://www.gcsescience.com/ex.htm http://www.gcsescience.com/ex1.htm http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/rocks/metalsrev1.shtml Complete the following table to show how different metals are extracted from their ores. In the column labelled notes on the method you should include general information only e.g. where the reaction takes place, temperature etc. Metal Method of extraction Notes on the method Aluminium (4 marks) Electrolysis. The aluminium ore bauxite is treated with sodium hydroxide to give alumina. As alumina has a very high melting point, it is dissolved in cryolite, Na3AlF6 to lower its melting point to about 900 °C. The resulting mixture is then electrolysed in a steel container with carbon (graphite) electrodes. The molten pure aluminium collects at the cathode at the bottom of the container and is siphoned off. Oxygen gas is given off at the anode. The temperature of the mixture undergoing electrolysis is kept at around 1100°C. Iron (6 marks) Reduction by carbon and/or carbon monoxide. The iron ore is heated at very high temperatures inside a blast furnace with coke (carbon) and limestone. The coke and the carbon monoxide that forms from the burning of carbon react with the iron ore to reduce it to iron metal. Due to the high temperature of the furnace, the iron melts to the bottom of the furnace from where it is collected. The limestone is added to remove the impurities present in the iron ore. The furnace is kept at a range of temperatures from 400 to 1800°C. Copper (6 marks) Thermal decomposition. The copper (II) ions in the ore are reduced to copper sulphide on heating and this copper sulphide is further reduced to copper metal by blasting it with hot air and this step releases sulphur dioxide. This impure copper is called blister copper and has to be purified before it can be used. . Copper (5 marks) Electrolysis. The blister copper needs to be purified through electrolysis before it can be used. The copper that has to be purified is kept as the anode, while the anode is made of pure copper. The electrolyte is copper (II) sulphate solution. The copper (II) ions dissolve from the anode and deposit on the cathode and hence pure copper is collected and the impurities settle at the bottom. The reaction takes place inside an electrolytic cell. 6. a) Which of the methods described do you think is most difficult to carry out? b) Which do you think is the most expensive to carry out. Give a reason for your answer? (3 marks) a) The electrolysis of aluminium is the most difficult to carry out because it requires the compounds to be molten at very high temperatures and the anodes need to be replaced regularly because the graphite anode is used up throughout the process. b) The electrolysis of aluminium is the most expensive because it requires large amounts of electricity which adds to the total cost, and the graphite anodes need to be replaced which also adds another material cost. 7. Why do you think that aluminium wasn’t discovered until 1825? What technological breakthrough was required before we could acquire aluminium metal? (2 marks) Aluminium wasn’t discovered until 1825 because electricity wasn’t produced cheaply at a large scale until then. The technological breakthrough that was required was the cheap and easy production of electricity. 8. Why does aluminium have to be extracted by electrolysis? (2 marks) Aluminium is a very reactive metal and is more reactive than hydrogen and copper, hence it cannot be extracted by simple thermal reduction on reaction with these two elements. 9. Why can iron be extracted by heating with carbon? (2 marks) Iron is less reactive than carbon hence carbon is able to reduce iron and get oxidized itself to carbon dioxide and carbon monoxide on heating and it can thus be extracting this way. 10. Copper can be extracted by heating with carbon, but the resulting copper is not very pure. Name one use where pure copper is essential. (you might want to refer back to your electrolysis notes). (1 mark) Pure copper is needed to make electrical wires because these wires need to be very good conductors of electricity. 11. Hydrogen could be used to reduce the copper oxide. Can you suggest a reason why carbon is used instead? (1 mark) Carbon is cheaper and more easily available whereas hydrogen is also an explosive gas hence its use adds a safety concern. Part 4 Metal prices Metal Price (in US dollars) per 100 grammes Iron 0.02 Lead 0.08 Gold 1200 Silver 14.00 Aluminium 0.12 Copper 0.24 Magnesium 0.32 12. Using the data from all of the tables (reactivity, abundance, method of extraction) presented so far, try and give reasons for the following: a) Why is aluminium more expensive than iron? (2 marks) Though aluminium is more abundant in the earth’s crust, there is a low percentage of aluminium in its ore hence extracting the metal from its ore is more difficult. Furthermore, the electrolysis of aluminium is very expensive, whereas the reduction of iron ores is comparatively cheaper. b) Why is gold more expensive than copper? (2 marks) Gold is more expensive than copper because it has a much lower percentage composition by mass in the earth’s crust by about a 1000 times. Gold is also more unreactive than copper, hence it is more valuable and more expensive. c) Why is copper more expensive than iron? Copper has a lower percentage composition by mass than iron in the earth’s crust. Furthermore, copper has to be purified through electrolysis before it can be used which adds to its extraction cost, making it more expensive than iron. (2 marks) Read More