Chapter 6- Electolysis Flashcards
What is electrolysis?
Electrolysis breaks down a substance using electricity
Can ionic compounds be electrolysed?
Yes, however they have to be either molten or dissolved in water. This is because their ions are then free to move and carry their charge to the elctrodes.
What is the cathode?
It is the negative electrode, positive ions move to this electrode
What is the anode?
It is the positive electrode, negative ions move to this electrode
What happens to the ions in electrolysis?
They move to the opposite charged electrode.
At the anode what happens to the ions?
Negative ions lose their extra electrons so are oxidised
At the cathode what happens to the ions?
The ions gain electrons so are reduced
What happens when an aqueous solution is electrolysed?
The less reactive element either the metal or hydrogen is usually produced at the cathode.
At the anode you get either oxygen gas from discharged hydroxide ions produced from water or a halogen is produced if the solution is a halide
How do you get aluminum oxide?
Bauxite is electrolysed in the extraction of aluminium metal
Why do they add cryolite to aluminium oxide?
To lower its melting point reducing the energy needed to extract the aluminium
When electrolysing bauxite what happens at the cathode and anode
Aluminum forms at the cathode and oxygen forms at the anode
What happens when you electrolyse sodium chloride solution?
You get three products.
Chlorine and hydrogen gas are given off at the electrodes
Sodium hydroxide solution left in solution
