Chemistry: Electrolysis_powerpoint-Nota.ppt

Notes to help students understand electrolysis

1. Electrolysis
Objectives
1.Write half equations for electrolysis.
2.Through observations establish the
products at the electrodes for your
aqueous salt.
3.To establish rules for deciding which
product is formed in aqueous
electrolysis.

2. Fuel cells
In a space rocket. Fuel cells react hydrogen
with oxygen:
2H
2+ O
2----2H
2O this makes
electricity and drinking water
Water is electrolysed to make oxygen:
2H
2O ----2H
2+ O
2

3. Electrolysis of Water
2H
2O ----2H
2+ O
2
Hydrogen used as a fuel
Oxygen made used in nuclear submarines
and spacecraft.

4. Half Equations for Water
Anode :
4OH
-
------------O
2+ 2H
2O + 4e
-
Cathode:
2H
+
+ 2e
-
-------H
2

5. Aqueous Salts
Copper chloride -Alex
Copper sulphate –Ian
Sodium Bromide –Charlotte
Potassium chloride –Harry
Magnesium chloride –Lucy
Potassium iodide –Ellen
Sulphuric acid –Kirsten/Jack
Hydrochloric acid –Harold/Cuong

6. Products
Compoundanode cathode
CuCl
2 Alex
CuSO
4 Ian
NaBr charlotte
KCl Harry
MgCl
2 Lucy
KI Ellen
H
2SO
4 Kirsten
HCl Harold

7. Discharge of Positive Ions
Gold Most easily discharged
Silver
Copper
Hydrogen
Lead
Iron
Zinc
Aluminium
Magnesium
Calcium
Sodium
Potassium

8. Discharge of Negative Ions
Iodine 2I
-
-2e
-
----I
2
Bromine
Chlorine
Oxygen 4OH
-
-4e
-
----O
2+ 2H
2O +
Sulphate

9. Homework
Write an essay on electrolysis:
‘Theory and uses of electrolysis’
Include:
Electrolysis of molten aluminium oxide
p.140-141
Look up electrolysis of aqueous salts on
wikepedia.