C6 - Electrolysis Flashcards
What is electrolysis?
The breaking down of an ionic compound (the electrolyte) using an electrical current.
How is electrolyis set up?
Two electrodes, one positive and one negative, are dipped in the electrolyte with a gap between them. These are connected to a battery, and are made out of mostly unreactive substances.
The electrolyte must be molten or liquid so that the ions can move.
As the battery is turned on, positively charged ions will move to the negative electrode, whilst negatively charged ions will move to the positive electrode.
When the ions reach the electrodes, they will lose their charge and become elements.
What is a half equation?
An equation where only points of interest are mentioned - in this case, only the ions and electrons.
Pb2+ + 2e- -> Pb
What happens when aqueous solutions are electrolyzed?
If the ion normally produced is higher on the reactivity series, hydrogen is produced at the negative electrode.
If not, hydroxide is given off at the negative electrode, and hydrogen at the positive electrode.
How is aluminium seperated from its ore?
- Aluminium ore purified to produce aluminium oxide.
- Aluminium oxide melted and dissolved in molten cryolite in preparation for electrolysis.
- Molten aluminium oxide is then electrolyised, producing aluminium at the negative electrode, and oxygen at the positive electrode.
What happens when brine is electrolysed?
Hydrogen gas produced at negative electrode.
Chlorine produced at positive electrode.
Sodium Hydroxide left behind as solution.
