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equipment for electrolysis
beaker → containing electrolyte
electrodes → ==cathode== and %%anode%%
electrodes joined with wire
what is electrolyte
liquid or solution containing an ionic compound, ions in electrolyte are free to move
what is an electrode
solid conductors, genrally made of metal/ carbon
what is the negative electrode called in electrolysis
cathode
what is the positive electrode called in electrolysis
anode
why are the electrodes joined by wire
so electrons can flow ( there is a power supply such as a battery to drive the flow of electrons)
meaning of the word electrolysis
splitting up with electricity
how does electrolysis work
negative ions attracted to anode and become discharged
positive ions attracted to cathode and become discharged
what does it mean to become discharged
go from a charged atom to a neutral atom
in the electrolysis of lead bromide, what happens at the anode
negative ions attracted to anode and are oxidised & become discharged
half equation
2Br- → Br2 + 2e-
in the electrolysis of lead bromide, what happens at the cathode
lead ions are combined with two electrons and are reduced to form pure lead
what’s happening in the wire in electrolysis
using electricity to convert the ions in a compound back into their pure elemental forms
how to reduce a metal
reduction with carbon (only works for metals less reactive than carbon)
electrolysis for those higher than metals
metals less reactive than carbon
zinc
iron
tin
lead
copper
silver
gold
how to make aluminium oxide into molten mix so it can be electrolysed
purify bauxite
mix it with cryolite to lower MP
melt
OIL RIG
oxidation is loss of electrons
reduction is gain of electrons
in aqueous solutions, what is the rule for which element is dicharged at the ==CATHODE==
If the metal element formed during electrolysis is more reactive than %%hydrogen%%, then hydrogen will be produced at the cathode.
If the metal element formed is less reactive than hydrogen, then the metal is produced at the cathode.
metals less reactive than hydrogen
copper
silver
gold
platinum
which element is carbon in between in reactivity series
aluminium & zinc
which element is hydrogen in between in reactivity series
lead & copper
in aqueous solutions, what is the rule for which element is discharged at the %%ANODE%%
if a %%HALIDE%% is present (aka group 7) it will be discharged
if not, then its %%ALWAYS%% the hydroxide which is discharged
why is the positive electrode continuously replaced
The positive electrode (anode) is made of carbon, which reacts with the oxygen to produce carbon dioxide and so must be continually replaced.
similarities between ppm and nm
• both have positive charges • both have (negative) electrons • neither has neutrons
why is graphite soft
each (carbon) atom forms three covalent bonds
forming layers (of hexagonal rings) (soft)
(because) layers can slide over each other
why is buckminister fullerene a good lubricant
molecules are spherical (so molecules) will roll
Explain why the scientist adds excess zinc rather than excess iodine.
to make sure that all the iodine reacts (as) excess iodine would remain in solution (so) iodine could not be filtered off or (so) the zinc iodide would not be pure
Suggest one reason why the percentage yield in this reaction is not 100%
incomplete reactions, in which some of the reactants do not react to form the product.
anything using temp changes, what can you use as a control to improve accuracy
polystryene cup