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Electrolysis L.O: To be able to describe the uses and predict the products of electrolysis.

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Presentation on theme: "Electrolysis L.O: To be able to describe the uses and predict the products of electrolysis."— Presentation transcript:

1 Electrolysis L.O: To be able to describe the uses and predict the products of electrolysis

2 Fuel cells In a space rocket. Fuel cells react hydrogen with oxygen: 2H 2 + O 2  2H 2 O this makes electricity and drinking water Water is electrolysed to make oxygen: 2H 2 O  2H 2 + O 2

3 Electrolysis of Water 2H 2 O  2H 2 + O 2 Hydrogen used as a fuel Oxygen made used in nuclear submarines and spacecraft. What is formed at the cathode and anode? What are the half equations

4 Half Equations for Water Anode : 4OH - ------------  O 2 + 2H 2 O + 4e - Cathode: 2H + + 2e - -------  H 2

5 Laptops In groups of 3 or 4 you need to research how aluminium extracted from bauxite is made by electrolysis. You need to be able to explain what happens during the electrolysis and what the products are. You have 30 mins! Include a diagram, half equations and an explanation

6 Electrolysis of aluminium Aluminium is a reactive metal that is found in the ore bauxite combined with oxygen as aluminium oxide (Al 2 O 3 ). Electrolysis breaks down the Al 2 O 3 into aluminium and oxygen. As the aluminium loses oxygen, reduction takes place. What is the word equation for the extraction of aluminium? aluminium oxide aluminium oxygen  + Aluminium ore (bauxite) has a very high melting point (2,050°C). In electrolysis, the ore is dissolved in a compound called cryolite (Na 3 AlF 6 ), which effectively lowers the melting point to 1,000 °C.

7 Aluminium from bauxite

8 Redox equations – aluminium What processes occur at the electrodes during the electrolysis of aluminium oxide (Al 2 O 3 )? What is the overall equation for this extraction by electrolysis? At the negative electrode: Al 3+ + 3e - Al (reduction)  At the positive electrode: 2O 2- O 2 + 4e - (oxidation)  aluminium oxide aluminium + oxygen 2 Al 2 O 3 (l) 4 Al (l) + 3 O 2 (g)  

9 Extracting aluminium summary


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