1. Mg(s) + Fe2+(aq) → Mg2+(aq) + Fe(s)
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A particular voltaic cell is made from magnesium and iron half- cells. The overall equation for the reaction occurring in the cell is
Mg(s) + Fe2+(aq) → Mg2+(aq) + Fe(s)
Which statement is correct when the cell produces electricity?
Magnesium atoms lose electrons.
The mass of the iron electrode decreases.
Electrons flow from the iron half-cell to the magnesium half-cell.
Negative ions flow through the salt bridge from the magnesium half-cell to the iron half-cell.
For each incorrect statement, explain why it is wrong.

2. Lesson 6-7
Electrolytic cells

3. Lesson 6-7: Electrolysis
Objectives:
Describe electrolytic cells
Identify at which electrode oxidation and reduction takes place
Understand how current is conducted in electrolytic cells
Deduce the products of electrolysis of a molten salt

4. Li+(l) + Cl-(l)  Li(s) + ½Cl2(g)
Electrolytic Cells
Electrolytic cells use electricity to provide the energy for an endothermic redox reaction
Electrolysis of lithium chloride:
Li+(l) + Cl-(l)  Li(s) + ½Cl2(g)
Current is carried by moving ions
Cations (+) move to the cathode (negative electrode)
Anions (-) move to the anode (positive electrode)
As ions need to be able to move, the ionic compound must be either:
Molten
Dissolved in solution
The opposite of a voltaic cell:
Voltaic cells turn stored chemical energy into electrical
Electrolytic cells turn electrical energy into stored chemical energy

5. Cations move to cathode
An Electrolytic Cell: e- e-
Bubbles of gas formed
ANODE
(+)
CATHODE
(-) X X M+
MOLTEN SALT or
SALT SOLUTION M+ M
Layer of metal formed M X- M+ M X- X-
Anions move to anode
Cations move to cathode

6. Products of Electrolysis
Assuming a molten simple metal salt involving only monatomic ions
Cathode – metal
Deposited on the surface of the electrode
Anode – non-metal
Typically as bubbles of gas
For example, electrolysis of molten magnesium bromide:
Cathode: a layer of magnesium metal (Mg2+ + 2e-  Mg)
Anode: bubbles of bromine gas (2Br-  Br2 + 2e-)
More complicated systems
Aqueous solutions – a range of possibilities depending on the stability of the ions relative to water
Polyatomic ions – a mixture of various products

7. By the end of the next lesson you should:
Complete the electrolysis of molten zinc chloride in the fume hood. Instructions here:
Produce an animation showing how electrolysis happens. Could be PowerPoint, flicker book, smart phone animation app, stop-motion (see: )...be creative.
Draw a Venn diagram comparing and contrasting electrolytic and voltaic cells
Write three potential internal-assessment research questions and on electrolytic or voltaic cells, select one and start producing a plan for it.

8. Key Points
Electrolysis uses electricity to drive endothermic redox reactions
Metal salts must be molten or dissolved so ions can move and carry charge
The negative cathode reduces positive metal ions
The positive anode oxidises negative non-metal ions