electrolysis Flashcards
How does electrolysis occur?
An electric current is used to break down an ionic substance
What is the substance that is broken down by electrolysis called?
The electrolyte
How is an electrical circuit for electrolysis set up?
- two electrodes which are dipped into the electrolyte
- one of these is connected to the positive terminal of a power supply (the anode)
- the other is connected to the negative terminal (the cathode)
What are the electrodes?
Conducting rods
What are the electrodes usually made of?
Inert (unreactive) substances, such as graphite or platinum
Why are electrodes made out of inert substances?
So that they do not react with the electrolyte or the products made in electrolysis
What happens to positively charged ions during electrolysis?
They move to the negative electrode (cathode)
What happens to negatively charged ions during electrolysis?
They move to the positive electrode (anode)
What happens to the ions when they reach the electrode?
They lose their charge and become elements
What can be given off / deposited at the electrodes?
Gases (given off) or metals (deposited)
What determines whether a gas is given off or a metal deposited at the electrodes?
This depends on the compound used and if it is molten or dissolved in water
Why do ionic substances not conduct electricity when they are solid?
This is because their ions are fixed in their giant lattice
What happens to the ions in an ionic substance when it is melted?
The ions are free to move around within the liquid and so carry their charge towards the electrodes
What is an alternative to melting some ionic substance to free it’s ions?
To dissolve it in water, which also enables the ions to become free to move around
Why is it more difficult to predict what will be formed when electrolysing ionic compounds in solution?
Because water also forms ions so the products at each electrode are not always exactly what should be expected
