SC11b Ores Flashcards
11.4 Recall that:
a) most metals are extracted from ores found in the Earth’s crust
b) unreactive metals are found in the Earth’s crust as the uncombined elements
11.7 Explain why the method used to extract a metal from its ore is related to its position in the reactivity series and the cost of the extraction process, illustrated by:
a) heating with carbon (including iron)
b) electrolysis (including aluminium)
Higher: 11.8 Evaluate biological methods of metal extraction.
what type of metals are found in their native state?
very unreactive metals
how are more reactive metals found in nature?
as compounds in rocks
what is extraction?
process of obtaining a metal from compounds
what is an ore?
rock that contains enough of a compound to extract a metal for profit
what ore contains iron oxide?
haematite
how is iron extracted from its compound?
heating the iron oxide with carbon which displaces the iron which leaves iron and cardon dioxide
Iron oxide + Carbon →
2Fe2O3 + 3C →
Iron + Carbon dioxide
4Fe + 3CO2
Can all metals be extracted by heating them with carbon?
no
what type of metals can be extracted by heating with carbon?
Only metals less reactive than carbon can be extracted using carbon.
Metals more reactive than carbon need to be extracted by a more powerful method.
how can more powerful metals be extracted?
electrolysis
how does extracting metals by electrolysis work?
Electrolysis involves passing electricity through a molten ionic compound to decompose it into its elements.
what ore is aluminium oxide found in?
bauxite
equation for the electrolysis of aluminium oxide with letter number equation
Aluminium oxide → Aluminium + Oxygen
2Al2O3 → 4Al + 3O2
negative of using electrolysis for extracting metals
very expensive as a lot of energy is needed
why are we starting to use new biological methods of extraction rather than heating with carbon? 2
~copper ores are running out
~biological methods don’t release harmful gases
negative of using the new biological methods?
take longer
what are the 2 biological methods of extraction?
~bioleaching
~phytoextraction
what is bioleaching?
~uses bacteria grown on a low grade ore
how does bio leaching work?
~bacteria is grown on a low grade ore
~the bacteria produces a solution containing copper ions, called a leachate.
~Copper is extracted from the leachate by displacement using scrap iron, then purified by electrolysis.
what metals can bio leaching be used on
~nickel
~cobalt
~zinc
~copper
what is phytoextraction?
growing plants that absorb metal compounds
how does phytoextraction work?
~Plants are grown
~Metals can be extracted from contaminated soils.
~The plants are burned to form ash, from which the metal is extracted.
advantages of bioleaching? 4
~no harmful gases produced
~less damage to the landscape than mining
~conserves supplies of higher grade ores
~does not require high temperatures
disadvantages of bio leaching? 2
~toxic substances and sulfuric acid can be produced by the process, and damage the environment
~very slow
advantages of phytoextraction? 5
~no harmful gases produced
~less damage to the landscape than mining
~conserves supplies of higher grade ores
~can extract metals from contaminated soils
disadvantages of phytoextraction? 3
~more expensive than mining some ores
~plants cant grow in some weather conditions
~very slow
Sodium is more reactive than aluminium. Describe a method to extract sodium from sodium chloride. Give a reason for your answer. (3 marks)
~Electrolysis.
~Sodium is more reactive than carbon
~so carbon cannot be used to extract it.
