Electrolysis

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

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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


1. ==Pb2+== **+** ==2e-== → Pb

what’s happening in the wire in electrolysis

1. the electrons from the negative ions are being passed to the positive anode
2. and then being transported along the wire around to the cathode (using the power of the battery)
3. these electrons are then given to the positive ion, discharging it

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*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.

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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