Electrolysis In Extracting Metals

Why can’t Aluminium be extracted with carbon?

Aluminium is MORE reactive than carbon so has to be extracted through electrolysis

What are the ions for Aluminium oxide

Aluminium ion = Al³+

Oxide ion = O²-

Why is Cryolite used with Aluminium Oxide - 1st step

Aluminium has a very high melting point so is mixed with cryolite to lower melting point

What does using Cryolite reduce (3 things)

Melting point

Amount of energy needed

so money is saved

what are electrodes made of? and Why?

Graphite (carbon)

it’s a great electrical conductor

has a high melting point so high temperatures can be used

other word for melted Aluminium Oxide

Molten - so ions can move freely

what is the aluminium ion? (symbol) Where is it attracted to?

Al³+

Cathode Negatvie

what is the Oxide ion? (symbol) Where is it attracted to?

O²-

Anode positive

what happens to Aluminium at the Cathode

each ion gains an electron to form a aluminium Atom

Half equation for reduction of Aluminium

Al³+ + 3e- ——> Al

what happens to the Oxide ion at the Anode?

each ion loses 2 electrons to form an oxygen atom

oxidation equation for oxide ions

O²- ———> O + 2e-

Why must the reaction equation at anode (oxide ion reaction) be doubled?

NEED O2 not just O

2O²- ———> O2 + 4e-

Why must the Anode be replaced regularly?

Electrodes are made from Graphite a form of Carbon! Oxygen can react to form CO²

C + O² ———> CO2

why is electrolysis EXPENSIVE!

Melting compounds (aluminium oxide ) requires LOADS of energy

LOADS OF ENERGY to produce electric current