electrolyisis

Question 1

positive electrode

Answer 1

anode
half equation: 2Cl- -> Cl2 + 2e-
- oxidation

Question 2

negative electrode

Answer 2

cathode
half equation
Cu2+ + 2e- -> Cu

Question 3

aluminium extraction

Answer 3

• graphite(carbon) anodes
• molten electrolyte + molten aluminium
• tank lined with carbon anode
• aluminium oxide
• positive elctrode: 2O2- -> O2 + 4e-
• negative electrode: Al3+ + 3e- -> Al
• positive electrode wears away over time and needs replacing. additional expense.
• the O2- are attracted to the +ve electrode and form O2
• the O2 reacts with the carbon to form CO2:

C + O2 -> CO2

Question 4

electrolysing brine

Answer 4

1) take the power pack and the two leads and connect them to the two carbon rods
2) red terminal is positive; black terminal is negative
3) add brine to the petri dish along with a few drops of UI solution
4) put the two carbon rods into the brine in the petri dish. keep them at opposite ends of the dish so you can see whats happening
5) turn on the power pack - try 6V
6) observe what happens at each electrode and write your observations in a table

Question 5

electroplating

Answer 5

• improve appearance eg stainless steal
• to protect from erosion eg galvanising
• positive electrode is plating metal
• electrolyte is solution of plating metal compound
• ## negative electrode is object to be plated