electrolysis Flashcards
why can’t solid ionic compounds conduct electricity
the ions are locked in place and are not free to move
what happens to an ionic compound when it is melted or dissolved in water
the electrostatic forces of attraction are broken and the ions are free to move
if the ions in an ionic compound or solution can move what does this allow
it allows electricity to be conducted
what are the liquids or solutions that allow electricity to be conducted
electrolytes
what are the two electrodes made of
why?
graphite
good conductor of electricity, high melting point
what is the negative electrode called
the cathode
what is the positive electrode called
the anode
in the electrolysis of molten led bromide what is attracted tot he negative electrode
the positive led ions
in the electrolysis of molten led bromide what is attracted to the positive electrode
the negative bromide ions
write the half equation for the led ions
is the oxidation or reduction
Pb2+ + 2e- —-> Pb
reduction because the led ion is gaining electrons to become an atom
write the half equation for the bromide ions
is this oxidation or reduction
Br- - e- —–> Br
oxidation because the bromide ion is loosing an electron to become an atom
for metals more reactive then carbon, how can they be extracted
through electrolysis
what are two uses of aluminum
drinks cans
air craft
what is the melting point of aluminum oxide like
very high round 2000 degrees celsius
when extracting aluminum from aluminum oxide why is cryolite used
to lower the melting point which reduces the amount of energy needed therefor saving money
where does the positive aluminum ions go and what is the half equation
they go to the cathode
Al3+ + 3e- —–> Al
where to the negative oxide ions go and what is the half equation
they go to the anode
0^2- ——> O + 2e-
why does the anode need to be replaced regularly
the oxygen molecules produced at the anode and react with the graphite (carbon), forming carbon dioxide gas
why is producing metals by electrolysis expensive
- melting the compound such as aluminum oxide requires lots of energy
- a lot of energy is required to produce the electrical current
what is formed when the water molecules ionize
hydrogen and hydroxide ions
from a copper sulfate solution what ions will go to the anode and the cathode
anode - sulfate, hydroxide
cathode - copper, hydrogen
what is the rule at the cathode when there is multiple things going there
hydrogen forms if the metal at the cathode is more reactive then hydrogen
in a copper sulphate solution what would be formed at the cathode
copper, less reactive then hydrogen
what is the rule at the anode when there is multiple things going there
oxygen forms unless the metal is a halide
why is platinum sometimes used for the electrodes
very unreactive metal
what is the half equation for the cathode
cu2+ + 2e- ——> cu
(reduction)
what is the half equation for the anode
4OH- ——-> o2 + 2H2O + 4e-
(oxidation)
required practical: electrolysis
- pour 50cm^3 of copper chloride solution in to the beaker
- place a plastic pertinent dish over it
- insert the electrodes through two holes in the Petri dish
- attach crocodile clips to the rods of a low-voltage power supply
- select 4V and turn it on
- copper should begin to coat the cathode, and bubbles of gas should begin forming (chlorine) at the anode
why do you have to make sure the two electrodes don’t touch
so you dont cause a short circuit
how do you test for chlorine gas
hold a blue piece of litmus paper, and if it begins to bleach then chlorine is present
