Electrolysis

Question 1

What occurs during electrolysis ?

Answer 1

an electric current is passed through an electrolyte . The ions move towards the electrodes, when they react and the compound decomposes.

The positive ions in the electrode will move towards the cathode , and gain electrons - reduced
The negative ions in the electrode will move towards the anode, and loss electrons - oxidised .

This creates a flow of charge through the electrolyte as the ions travel to the electrode. As ions gain or lose electrons, they form the uncharged element and are discharged from the electrolyte

Question 2

How molten ionic compounds are electrolysed

Answer 2

1) An ionic solid can’t be electrolysed because the ions are in fixed position and can’t move
2) Molten ionic compound can be electrolysed because the ions are free to move and conduct electricity
3) Molten ionic liquids e.g. lead bromine are always broken down up into their elements
4) + metal ion reduced to element at cathode, - metal ion oxidised to element at anode

Question 3

If a metal is too reaction to be reduced with carbon or reacts with carbon, then what process can be used to extract it and what are the disadvantages of this ?

Answer 3

Electrolysis

Expensive as lots of energy required to melt the ore and produce the required current

Question 4

Metals can be extracted from their ores using electrolysis
How?

Answer 4

• Aluminium extracted from ore bauxite by electrolysis . Bauxite contains Al203
• Al203 has a very high melting temp so it’s mixed with cryolite to lower mp
• The molten mixture contains free ions - so it’ll conduct electricity
• The positive Al ^3+ ions are attracted to the negative electrode, where they each pick up 3 electrons and turn into neutral AL atoms. These then sink to the bottom of the electrolysis tank
• The negative O^2- ions are attracted to the + electrode where they each lose two electrons . The neutral oxygen atoms combine to form O2 molecules

Question 5

At the negative electrode

Answer 5

Reduced

Al^3+ + big 3 e^- –> Al

Question 6

At the positive electrode

Answer 6

oxidised

big 2 O^2- –> O2 + big 4 e^-

Question 7

What is the anode made of ?

Answer 7

Carbon and needs to be replaced regularly as it reacts with oxygen to produce CO2