2e Extraction and uses of metals Flashcards
(20 cards)
Where are ores found?
In the Earth’s Crust
What metals are found native?
- Some metals such as gold are found native (chemically uncombined)
How are other metals found?
- Most metals are found as minerals (naturally occurring metal compounds) in the earth’s crust
Why are some metals found as minerals?
- When the earth was formed there was such intense heat and pressure that chemical reactions would have caused elements to combine and form metal compounds
- Consequently many useful metals are locked up as metal oxides and metal sulfides. Rocks that contain enough compound to be worthwhile extracting is known as an ore
How can you obtain a metal from its ore?
- To obtain a metal from its ore, the compound must be split up.
- One method is to heat metal oxides with carbon. If the metal in the compound less reactive than carbon then it will be displaced from its compound
What does iron oxide + carbon produce?
iron oxide + carbon -> iron + carbon dioxide
- The iron has lost oxygen it has been reduced in a redox reaction.
- The carbon has gained oxygen it has been oxidised in a redox reaction
Where is carbon in the reactivity series?
- Carbon fits between Aluminium and Zinc in the reactivity series. It will displace any metal below from its compound
What is an Oxidising agent?
A substance that oxidises another substance (The oxidising agent is reduced)
What is the reducing agent?
A substance that reduces another substance
(The reducing agent is oxidised)
Why does gold not need to be extracted from ores?
Gold does not need to be extracted from ores because it is already found as an element so there’s no need for it to be extracted. It is unreacted
What is an ore?
A rock that contains a compound from which a metal can be extracted for a profit
Why can’t calcium be extracted by heating calcium chloride with carbon?
Calcium cannot be extracted by heating it with carbon because calcium is more reactive than carbon so the carbon won’t be able to displace the calcium
Why does the extraction of calcium from calcium chloride involve a reduction reaction?
Because calcium ions need to gain electrons in order to become a neutral calcium atom
One method of extracting zinc involves the reaction of zinc oxide with carbon. Explain, both in terms of oxygen and electrons, why this extraction involves reduction
This extraction involves reduction because to be able to extract the metal from the metal oxide you need the carbon to displace it as its more reactive so the zinc loses oxygen. Zinc ions also gain electrons when extracted to form metal atoms.
Why can lead be extracted by heating with carbon?
Lead can be extracted by heating with carbon because it is less reactive than carbon so it s able to displace lead from its compound
Why is this a redox reaction?
This is a redox reaction because both reduction and oxidation occur. The lead it displaced so it loses its oxygen so it reduces and the carbon gains the oxygen so it is oxidised
Which elements are already found as elements in the earth’s crust?
Gold, Platinum
Which elements can be extracted using thermal decomposition
Mercury, Silver
Which elements can be extracted by displacement using carbon?
Copper, lead, tin, nickel, iron, chromium, zinc
Which elements can be extracted by using electrolysis?
Aluminium, magnesium, calcium, sodium, potassium
