electrolysis

Question 1

why can’t solid ionic compounds conduct electricity

Answer 1

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

Question 2

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

Answer 2

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

Question 3

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

Answer 3

it allows electricity to be conducted

Question 4

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

Answer 4

electrolytes

Question 5

what are the two electrodes made of
why?

Answer 5

graphite
good conductor of electricity, high melting point

Question 6

what is the negative electrode called

Answer 6

the cathode

Question 7

what is the positive electrode called

Answer 7

the anode

Question 8

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

Answer 8

the positive led ions

Question 9

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

Answer 9

the negative bromide ions

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

through electrolysis

Question 13

what are two uses of aluminum

Answer 13

drinks cans
air craft

Question 14

what is the melting point of aluminum oxide like

Answer 14

very high round 2000 degrees celsius

Question 15

when extracting aluminum from aluminum oxide why is cryolite used

Answer 15

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

Question 16

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

Answer 16

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

Question 17

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

Answer 17

they go to the anode
0^2- ——> O + 2e-

Question 18

why does the anode need to be replaced regularly

Answer 18

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

Question 19

why is producing metals by electrolysis expensive

Answer 19

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

Question 20

what is formed when the water molecules ionize

Answer 20

hydrogen and hydroxide ions

Question 21

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

Answer 21

anode - sulfate, hydroxide
cathode - copper, hydrogen

Question 22

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

Answer 22

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

Question 23

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

Answer 23

copper, less reactive then hydrogen

Question 24

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

Answer 24

oxygen forms unless the metal is a halide

Question 25

why is platinum sometimes used for the electrodes

Answer 25

very unreactive metal

Question 26

what is the half equation for the cathode

Answer 26

cu2+ + 2e- ——> cu
(reduction)

Question 27

what is the half equation for the anode

Answer 27

4OH- ——-> o2 + 2H2O + 4e-
(oxidation)

Question 28

required practical: electrolysis

Answer 28

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

Question 29

why do you have to make sure the two electrodes don’t touch

Answer 29

so you dont cause a short circuit

Question 30

how do you test for chlorine gas

Answer 30

hold a blue piece of litmus paper, and if it begins to bleach then chlorine is present