Electrochemistry

Question 1

Electrolyte

Answer 1

Substance that conducts electricity when molten or dissolved in water with chemical reactions at the electrodes.

Question 2

Non-electrolyte

Answer 2

Substance that doesn’t conduct in liquid phase.

Question 3

Electrolysis

Answer 3

Electrolysis is the breakdown of an ionic compound (molten or aqueous solution) by the passage of electricity.

Question 4

Electrodes

Answer 4

Pieces of metal or carbon through which current enters and leaves the electrolyte.

Question 5

Cathode (-)

Answer 5

Cations (hydrogen & metal ions) accept electrons from the cathode.
E.g. Cu2+ + 2e- = Cu
2H + 2e- = H2
Al3 + 3e- = Al

Question 6

Anode (+)

Answer 6

Anions (non metals) are attracted to the anode. Electrons flow from the anode to the battery.

Question 7

If Anode is inert

Answer 7

If the anode is inert (i.e. carbon or platinum) the negative ions lose electrons to the anode:

2Cl- - 2e- = Cl2
4OH- - 4e- = 2H2O + O2

Question 8

If the anode is not inert

Answer 8

If the anode is not inert (i.e. silver, copper, or other reactive metals) the metal atoms of the anode lose electrons and form positive ions. The anode will therefore dissolve and become smaller:

Cu - 2e- = Cu2+
Zn - 2e- = Zn2+

Question 9

Concentrated solution

Answer 9

In a concentrated solution, Cl- will be discharged (attracted to electrode) rather than OH-

In a dilute solution on the other hand, OH- will be discharged instead.

Question 10

Main ore of aluminium is called

Answer 10

Bauxite

Question 11

pure aluminium oxide

Answer 11

Alumina

Question 12

Cryolite

Answer 12

The point in cryolite is to lower the temperature and improve conductivity.