Electrolysis

Question 1

What are the names of the elctrodes?

Answer 1

• Cathode (negative)
• Anode (positive)

Question 2

What way do the electrons flow?

Answer 2

• Positive to negative
• Anode to cathode

Question 3

Which electrode do metals and gases go to?

Answer 3

• Metals form positive ions and so go to the cathode
• Gases form negative ions and so go to the anode

Question 4

What happens at the anode and cathode during the elctrolysis of aluminium oxide?

Answer 4

• Anode:
• Oxygen atoms each give up 2 electrons and float off
• 2O(2-) = O2 + 4e(-)
• Cathode:
• Auminium atom gains 3 electrons each and forms solid layer at the bottom
• Al(3+) + 3e(-) = Al

Question 5

What are the steps of the elctrolysis of auminium oxide (preperation)?

Answer 5

• Purify bauxite to get aluminium oxide
• Mix aluminium oxide with cryolite to reduce melting point
• Melt aluminium oxide so the ions are free to move
• Electrolyse

Question 6

What happens at the anode and cathode during electrolysis of an aqeuous solution?

Answer 6

• Anode:
• Non-metal and hydroxide ions are attracted
• Always hydroxide ion discharged unless halide ion present
• 4OH- = 2H2O + 4e-
• Cathode:
• Metal and hydrogen ions are attracted
• Always hydrogen ion discharged unless metal is less reactive (copper)