4.3 Electrolysis
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What happens in the electrolysis of NaCl?
NaCl is dissolved or molten Electrical current is passed through NaCl separates into ions, Na is in group 1 therefore is an Na+ ion Cl is in group 7 therefore is a Cl- ion These ions then want to become neutral to reform elements Na+ (as it is positively charged) will move to the negative electrode and regain an electron Na+ + e- -> Na Reforming the element Na Cl- then moves to the positive electrode to donate an electron 2Cl- -> Cl2 + 2e- Both elements are reformed, chlorine and sodium
What is the process of electrolysis?
When an ionic compound is melted or dissolved Ions are free to move throughout the liquid or solution Ions are able to carry charge A current is then passed through, so ions can move to the electrodes to then reform elements
What are the positive and negative electrodes called?
Positive = Anode Negative = Cathode
When do we use electrolysis to extract pure metals?
When the metals are more reactive than carbon They are too reactive to be extracted by reduction of carbon, so they are extracted by electrolysis instead
Why is electrolysis an expensive process?
• Needs large amounts of energy to melt the metal compounds • Needs large amounts of energy to produce the elctrical current
How is aluminium manufactured?
Electrolysis of aluminium oxide and cryolite Aluminium oxide has a very high melting point, its mixed with cryolite to reduce it so we dont need as much energy
What type of equation is used to represent the reaction at an electrode?
Half equations e.g. 2Cl- -> Cl2 + 2e-