Electrolysis

Question 1

How is electricity conducted in a metal?

Answer 1

• the flow of electrons or electrical current
• doesn’t make a chemical change
• lots of compounds conduct electricity when molten or in solution
• which will show signs of a chemical reaction when they conduct

Question 2

What is electrolysis?

Answer 2

A chemical change caused by passing an electrical current through a compound either molten or in solution. Electricity is used to split the compound into elements.

Question 3

What is an electrolyte?

Answer 3

A substance that undergoes electrolysis so contains ions.
- covalent compounds don’t contain ions so can’t be electrolytes

Question 4

What is an electrode?

Answer 4

They pass electricity into and out of the electrolyte.

Question 5

What substances are used as electrodes and why?

Answer 5

• carbon - it conducts electricity and is fairly unreactive
  -platinum - unreactive, but is rarer and more expensive

Question 6

Which is the positive electrode?

Answer 6

Anode
(PANC)

Question 7

Which is the negative electrode?

Answer 7

Cathode
(PANC)

Question 8

What happens at the cathode?

Answer 8

-positive ions move there
-when ions reach electrode, gain electrons (reduced)

Question 9

What happens at the anode?

Answer 9

-negative ions move here
-when ions reach electrode, lose electrons (oxidised)

Question 10

What is OILRIG?

Answer 10

O - oxidation
I - is
L - loss (of electrons)
R - reduction
I - is
G - gain (of electrons)

Question 11

How do ionic substances undergo electrolysis?

Answer 11

-very high melting points - too much energy to have them molten
- can dissolve them in water - ions can still move around & carry charge

Question 12

How do you know what will be produced at anode?

Answer 12

Is anion group 7 element?
yes - halogen gas
no - oxygen gas

Question 13

How do you know what will be produced at cathode?

Answer 13

Is the cathode less reactive than hydrogen?
yes - less reactive metal produced
no - hydrogen gas produced

Question 14

What is native state?

Answer 14

found as pure metal, not bonded to another substance

Question 15

How does metal extraction using carbon work?

Answer 15

the metal has to be less reactive than carbon, so carbon will displace the metal from its ore, carbon is then oxidised which reduces the metal

Question 16

Should you extract aluminium by electrolysis?

Answer 16

no
- aluminium oxide has very high melting point
- requires too much energy/money to melt
- aluminium oxide is dissolved in molten cryolite which has lower melting point (<1000C)