IGCSE Chemistry - Extraction & Reactivity Series
What is an alloy
a mixture of two or more elements, at least one of which is a metal
Carbon extraction
carbon extraction is used only with metals that are less reactive than itself so that it is able to displace the metal from the ore.
Metal extraction methods
- extraction by heating with carbon - electrolysis - phytoextraction - bacterial extraction
What methods of rust prevention are used
- painting, coating with plastic and the use of oil or grease all prevent rust as it excludes oxygen and water. - Sacrificial protection is the galvanising of a metal with a more reactive metal which will rust first and prevent water & oxygen from reaching the layer underneath
What is a displacement reaction?
A reaction in which a more reactive element takes the place of a less reactive element in a compound. It is easily seen when a salt of the less reactive metal is in the solution. the more reactive metal gradually disappears and the less reactive metal forms a coat on the surface of the more reactive metal.
How does electrolysis work to extract metals?
Electrolysis has a positive electrode which is the anode, and a negative electron which is the cathode. Positive ions are attracted to the cathode where they are reduced and gain electrons to form an atom, and negative ions are attracted to the anode where they undergo oxidation and lose electrons.
What metal does not react with water, acid or oxygen?
Gold. It is the least reactive metal in the reactivity series as it does not react at all.
Electrolysis of Aqueous Solutions
In an aqueous solution, water ionises to form H+ and OH- ions. This needs to be considered as well, as there would be two possible ions that could be attracted to each electrode. At the cathode, hydrogen is produced if the metal is more reactive than hydrogen. At the anode, oxygen is produced unless the solution contains halide ions in which case the halogen will be produced at the anode.
What are the products of a metal reacting with acid?
Metal + Acid -> Salt + hydrogen
What are the products of a metal reacting with cold water
Metal + Water -> Metal hydroxide (an alkaline solution) + hydrogen
What are the products of a metal reacting with oxygen?
Metal + oxygen -> Metal oxide
What is metal extraction
Metal extraction is the removal of a metal from ores found in the earth's crust. Metals like gold do not require metal extraction as they are found as native metals due to their unreactive nature.
How are metals arranged in a reactivity series
Metals are arranged based on their reaction with water, oxygen and acids.
Electrolysis metal extraction
Metals that are more reactive than carbon are extracted by electrolysis which is very expensive. Alumnium is produced by electrolysis -- electrolysis requires metals to be molten so that they are able to conduct electricity.
Under what conditions does iron rust?
Oxygen and water are necessary for iron to rust
Why are alloys harder than pure metals?
the different sized atoms of the metals distort the layers in the structure, making it more difficult for them to slide over each other.