Electrolysis and extracting metals

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  • Created by: Jan Shah
  • Created on: 27-04-13 12:57
What is a electrolytes?
It is a substance that undergoes electrolysis. All electrolytes contain ions.
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What does electrolysis involve?
It involves the formation of new substances when ionic compounds conduct electricity.
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What happens in electrolysis?
In electrolysis electricity is passed into and out of the electrolyte via two electrodes.
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What is the positive electrode called and why?
It is called the anode because it attracts anions.
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What is the negative electrode and why?
A negative electrode is called the cathode because it attracts cations.
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What are the electrodes made from?
The electrodes are made from carbon (graphite).
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Describe the electrolysis of Lead (II) Bromide.
PbBr2 is an ionic compound with a giant lattice structure. In the solid state ions cannot move so it cannot conduct electricity but when heated it becomes molten so giant crystal lattice structure breaks down. The ions are free so conduct electricity
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In the electrolysis of lead bromide what happens at the negative electrode or cathode?
At the cathode the lead ions recieve 2 electrons to from molten lead metal which collects at the below the electrode.
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What happens at the positive electrode or the anode?
The bromide ions lose one electrons to form neutral bromine atoms which combine to form bromine molecules. The bromine gas are seen at the anode.
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Label this blast furnace.
a
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What happens inside a blast furnace?
Coke is impure carbon which is the reducing agent and undergoes combustion to produce carbon dioxide. The carbon dioxide is then reduced by the carbon at high temperatures which produces carbon monoxide.
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What happens inside a blast furnace (continued)?
The carbon monoxide is the main reducing agent in the balst furnace. The haematite (iron (III) oxide) is reduced to pure iron by the carbon monoxide.
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What is the word and chemical equation between carbon and oxygen?
Carbon + oxygen = carbon dioxide, C + O2 = CO2
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What is the word and chemical equation between carbon and carbon dioxide?
Carbon + carbon dioxide = carbon monoxide, C + CO2 = 2CO
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What is the word and chemical equation between carbon monoxide and iron (III) oxide?
Carbon monoxide + iron (III) oxide = 3CO + Fe2O3 = 2Fe + 3CO2
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Why is the first reaction between carbon and oxygen important?
It is important because it gives out heat (exothermic) and helps to maintain high temperatures in the furnace.
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What is the role of limestone in a blast furnace?
Limestone is calcium carbonate and undergoes thermal decomposition at high temperatures. It is added to the furnace to remove impurities and forms calcium oxide.
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Write the word and chemical equation of the thermal decomposition of calcium carbonate.
CaCO3 = CaO + CO2, Calcium carbonate = calcium oxide + carbon dioxide.
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What does calcium oxide react with to form what?
The basic calcium oxide reacts with acidic oxides such as silicon dioxide to form calcium silicate (liquid ****).
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Write the chemical and word equation for calcium oxide silicon dioxide.
Calcium oxide + silicon dioxide = calcium silicate, CaO + SiO2 = CaSiO3
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What is the main ore of iron and how is it extracted?
The main ore is haematite (iron (III) oxide and it is extracted by a blast furnace.
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What is the main ore of aluminium and how is it extracted?
The main ore is bauxite and is extracted by electrolysis.
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Label this diagram.
a
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Write the ionic half equation for aluminium.
Al3+ + 3e- = Al
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Write the ionic half equation for oxygen.
2O2- = O2 + 4e-
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Why does carbon dioxide form in extracting aluminium?
It forms due to the high temperatures during the extraction of aluminium as the oxygen produced reacts with teh carbon in the anode.
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In the blast furnace why does the liquid **** float on top of the iron?
It floats as it is less dense than the iron.
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Give two uses and the reason why they are used for iron.
It can be used for: car bodies as it is strong (can withstands collisions, iron nails because it is strong, ships, girders and bridges because it is strong.
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Give two uses and the reason why they are used for aluminium.
It can be used for: Aeroplane bodies because it has a high strength - weight ratio, overhead power cables because it is a good conductor of electricity, saucepans - good conductors of heat, food cans - non-toxic, window frames - resists corrosion.
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Why can aluminium not be extracted from a blast furnace?
Because aluminium is more reactive than carbon.
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Write the ionic half equation for extracting iron at the positive electrode.
2Br- = Br2 + 2e-
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Write the ionic half equation for extracting iron at the negative electrode.
Pb2+ + 2e- = Pb
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Where does oxidation and reduction happen?
Oxidation happens at the anode and reduction happens at the cathode.
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Other cards in this set

Card 2

Front

What does electrolysis involve?

Back

It involves the formation of new substances when ionic compounds conduct electricity.

Card 3

Front

What happens in electrolysis?

Back

Preview of the front of card 3

Card 4

Front

What is the positive electrode called and why?

Back

Preview of the front of card 4

Card 5

Front

What is the negative electrode and why?

Back

Preview of the front of card 5
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