Electrolysis Flashcards
What is electrolysis?
Breaks down a substance using electricity
Positive and negative ions in Electrolysis
Positively charged ions → cathode
Negatively charged ions → anode
Difference between cathode and anode
Cathode = negative electrode Anode = positive electrode
What happens when ions reach electrodes?
They lose their charge and become elements
Gases may be given off or metals deposited
(these reactions depends on compound used and whether it is molten or dissolved in water)
Do ionic compounds conduct electricity?
No, they are solid
Ions are in fixed positions in giant lattice
If melted = can conduct electricity
Ions free to move around within hot liquid
Carry their charge towards the electrodes
zin chloride → zinc + chlorine
Positive Zn2+ move towards cathode
Negative Cl- move towards anode
Chlorine produces gas at anode
Zinc coats tip of cathode
What does Electrolysis need to occur?
The compound must contain ions
Why can’t covalent compounds be broken down by electrolysis
Because they contain neutral atoms
Electrolysis of solutions
High melting points → lots of energy to melt them and free ions to move electrodes
Difficult to predict what ionic compounds will form not as molten
In electrolysis only metals of low reactivity are deposited from aqueous solutions
Why can ionic compounds only be electrolysed when molten or dissolved in water?
Ions are free to move and carry their charge to electrodes
What are electrodes made up of?
Unreactive substance
Such as graphite
What happens when ions reach electrode in terms of electrons?
Negatively charged ions lose electrons → become neutral atoms
Positively charged ions gain electrons → become neutral atoms
If ions gain electrons at electrode they become…
reduced
OIL RIG
Reduction and Oxidation at cathode and node
Anode → positive electrode → oxidation
Cathode → negative electrode → reduction
Extraction of aluminium
Lots of energy
High melting point
Purify aluminium then melt aluminium oxide
If melted → ions can move to electrodes
Large amount of electrical energy that is transferred to electrolysis cells keep mixture molten
