Electrolysis Flashcards
Ionic compounds contains…
Charged atoms called ions.
Ionic solids
Ions are locked and cannot move, so it does not conduct electricity.
When ionic compound dissolved or molten
Ions are free to move so it can carry the charge.
Electrolysis
Passing an electric current through a molten or dissolved ionic compound. It breaks down to its elements.
E.g. lead bromide = lead + bromide
Electrolyte
Is molten or dissolved ionic compound that we pass the electric current through.
Ions in electrolysis
Positive ions are attracted to negative electrode. Negative ions are attracted to positive electrode.
Electrode
Is made of materials which conduct electricity such as graphite.
Electroplating
Objects can be plated in metal, if we make them into the negative electrode.
Positive metal ions move to….
negative electrode and stick there crating layer of metal.
Uses of Electroplating
- protect metals from corrosion
- make the object look more attractive
- to increase the hardness of a surface area
- to save money, creating a thin layer of an expensive metal
Positive electrode
Anode
Negative electrode
Cathode
Positive Ions
Cathodes
Negative Ions
Anodes
Ionic substances have…
a very high melting point, so it takes a lot of energy to melt them. However, some can be dissolved in water, creating free ions also.
Only metals of low reactivity, below…
hydrogen in the reactivity series are deposited from the aqueous solution. E.g. copper Otherwise, hydrogen gas is produced.
Covalent compounds cannot usually…
be electrolysed unless they react in water to form ions.
Water forms…
hydrogen ions and hydroxide ions
It is important that electrode does not…
react with the solution. Platinum is often used as it is very unreactive metal.
Inert
Means it is not reactive.
Ionise
Means split.
What is produced at anode?
If the aqueous solution contains halide ions then the halogen(gas) will be produced at the anode.
The half-equation of halogens
2H- + 2e- = H2
2Cl- = Cl2 + 2e-
Active electrodes
Take part in the electrolysis.
