Chatpter 10 Electrolysis Flashcards
What is Electrolysis?
Electrolysis is the splitting of a compound to its elements by passing electricity through it.
What are the conditions for electrolysis?
For electrolysis to work, the ions must be free to move. Ions are free to move when an ionic substance is in the aqueous state (dissolved in water) or molten (liquid state).
are ionic compounds good electrolytes when they are solids?
Assolids, ionic compounds cannot
conduct electricity because their
ions are bonded strongly together in
the lattice and cannot move and
carry charge
are ionic compounds good electrolytes when they are liquids?
When liquid (molten), ionic
compounds conduct electricity. The ions
can break free of the lattice and are able
to move. The ions are charged particles
and so can carry an electric current.
Ionic compounds can also conduct electricity when they are dissolved in
water (aqueous). When dissolved, the ions become free to move and can carry
an electric current.
Tell me some good electrolytes
All ionic compounds, strong acids(HCl, HNO3, H2SO4),
water - All of these dissociate into free ions in water
How does electrolysis work?
- Electrodes attached to a DC electricity supply
are placed into the molten or a solution of the
electrolyte. - Positive ions (cations) from the electrolyte move
(migrate) towards the negative electrode (the
cathode). - Negative ions (anions) from the electrolyte move
(migrate) towards the positive electrode (the anode).
What happens at the cathode?
POSITIVE IONS become neutral by gaining electrons from the
cathode
What happens at the anode?
NEGATIVE IONS become neutral by losing electrons to the anode
Which ions discharge more easily than hydrogen ions?
Copper Silver Gold Platinum
Which ions discharge more easily than Hydroxide ions?
Iodide Bromide chloride
What are the properties the electrodes must have and why?
Some of the products of electrolysis are very
reactive substances or corrosive solutions,
for this reason the electrodes used must be
made from a material that is
- inert (unreactive) so the products will not
react with the electrodes - good conductors of electricity
Explain why the electrolysis of acidified water produces twice as much hydrogen as oxygen.
The formula for water is H2O so it contains twice as many hydrogen atoms as oxygen atoms. Or 4 electrons are needed to produce 1 molecule of oxygen and 4 electrons will produce 2 molecules of hydrogen.
What is electroplating?
Coating the surface of a metal with a thin layer of
another metal. E.g. coating the surface of iron with silver.
How does electroplating work?
How electroplating works:
Cathode: is the object to be plated e.g an iron
fork
Anode: the pure metal e.g silver (to cover the
iron fork in a layer of silver)
Electrolyte: contains ions of the plating metal
e.g: silver nitrate solution (contains silver ions)
What are some uses of electroplating?
- Silver or gold plating is used to make
jewellery that is cheaper than using the pure
metal - Electroplating metals that corrode easily such
as iron with metals that are resistant to
corrosion e.g coating iron/steel with zinc
also called ‘galvanized zinc’
