electrolysis Flashcards

1
Q

why can’t solid ionic compounds conduct electricity

A

the ions are locked in place and are not free to move

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2
Q

what happens to an ionic compound when it is melted or dissolved in water

A

the electrostatic forces of attraction are broken and the ions are free to move

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3
Q

if the ions in an ionic compound or solution can move what does this allow

A

it allows electricity to be conducted

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4
Q

what are the liquids or solutions that allow electricity to be conducted

A

electrolytes

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5
Q

what are the two electrodes made of
why?

A

graphite
good conductor of electricity, high melting point

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6
Q

what is the negative electrode called

A

the cathode

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7
Q

what is the positive electrode called

A

the anode

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8
Q

in the electrolysis of molten led bromide what is attracted tot he negative electrode

A

the positive led ions

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9
Q

in the electrolysis of molten led bromide what is attracted to the positive electrode

A

the negative bromide ions

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10
Q

write the half equation for the led ions
is the oxidation or reduction

A

Pb2+ + 2e- —-> Pb
reduction because the led ion is gaining electrons to become an atom

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11
Q

write the half equation for the bromide ions
is this oxidation or reduction

A

Br- - e- —–> Br
oxidation because the bromide ion is loosing an electron to become an atom

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12
Q

for metals more reactive then carbon, how can they be extracted

A

through electrolysis

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13
Q

what are two uses of aluminum

A

drinks cans
air craft

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14
Q

what is the melting point of aluminum oxide like

A

very high round 2000 degrees celsius

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15
Q

when extracting aluminum from aluminum oxide why is cryolite used

A

to lower the melting point which reduces the amount of energy needed therefor saving money

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16
Q

where does the positive aluminum ions go and what is the half equation

A

they go to the cathode
Al3+ + 3e- —–> Al

17
Q

where to the negative oxide ions go and what is the half equation

A

they go to the anode
0^2- ——> O + 2e-

18
Q

why does the anode need to be replaced regularly

A

the oxygen molecules produced at the anode and react with the graphite (carbon), forming carbon dioxide gas

19
Q

why is producing metals by electrolysis expensive

A
  1. melting the compound such as aluminum oxide requires lots of energy
  2. a lot of energy is required to produce the electrical current
20
Q

what is formed when the water molecules ionize

A

hydrogen and hydroxide ions

21
Q

from a copper sulfate solution what ions will go to the anode and the cathode

A

anode - sulfate, hydroxide
cathode - copper, hydrogen

22
Q

what is the rule at the cathode when there is multiple things going there

A

hydrogen forms if the metal at the cathode is more reactive then hydrogen

23
Q

in a copper sulphate solution what would be formed at the cathode

A

copper, less reactive then hydrogen

24
Q

what is the rule at the anode when there is multiple things going there

A

oxygen forms unless the metal is a halide

25
why is platinum sometimes used for the electrodes
very unreactive metal
26
what is the half equation for the cathode
cu2+ + 2e- ------> cu (reduction)
27
what is the half equation for the anode
4OH- -------> o2 + 2H2O + 4e- (oxidation)
28
required practical: electrolysis
1. pour 50cm^3 of copper chloride solution in to the beaker 2. place a plastic pertinent dish over it 3. insert the electrodes through two holes in the Petri dish 4. attach crocodile clips to the rods of a low-voltage power supply 5. select 4V and turn it on 6. copper should begin to coat the cathode, and bubbles of gas should begin forming (chlorine) at the anode
29
why do you have to make sure the two electrodes don't touch
so you dont cause a short circuit
30
how do you test for chlorine gas
hold a blue piece of litmus paper, and if it begins to bleach then chlorine is present