- Slides: 11
� Magnesium � Aluminium � Zinc � Iron � Copper Magnesium can displace copper from copper oxide – WHY? Mg (s) + Cu. O (s) → Mg. O + Cu
Mg + Cu 2+O 2 - → Mg 2+02 - + Cu As you can see the oxide ions have NOT been changed they have just got a different partner. Therefore they are called the SPECTATOR IONS. The Magnesium ATOMS have changed into Magnesium IONS by losing 2 electrons. The Copper ions have become atoms again by gaining 2 electrons.
Make sure you can see how the 2 equations you just saw are linked. Now turn it into an IONIC equation - leave out the spectator ions: Mg +Cu 2+ → Mg 2+ + Cu Can you see what has happened to the Magnesium atoms? They have turned into Magnesium ions Can you see what has happened to the Copper ions? They have turned into Copper atoms. HOW DO ATOMS TURN INTO IONS?
� Mg → Mg 2+ + 2 e� Magnesium has LOST 2 electrons to make the Magnesium ION. � Make sure you BALANCE the number of electrons Magnesium + Cu 2+ + 2 e- → Cu � Copper ion has GAINED 2 electrons (from Magnesium) to make the Copper ATOM. � Copper
Now we need a different definition for OXIDATION and REDUCTION OXIDATION is the LOSS of Electrons REDUCTION is the GAIN of Electrons OILRIG
� Magnesium Oxidised? � Copper Reduced?
Remember salts are things like Copper Sulphate. Zn(s) + Cu S 04 → Zn. S 04 (aq) + Cu (s) Lets look at the ionic equations for this reaction Zn + Cu 2+ S 04 2 - → Zn 2+ S 04 2 - + Cu The sulphate ion is the spectator ion so we remove it Zn + Cu 2+→ Zn 2+ + Cu
� Zinc � Copper � Why? � It has LOST electrons Oxidised? has GAINED electrons Reduced?
� Zn → Zn 2+ + 2 e- Zinc � Cu 2+ + 2 e- → Cu Copper