C6b Redox Reactions
Rusting is an example of a redox reaction. You studied Rusting in C2 but here is a
What conditions are needed for rusting?
1. Boiled water –
2. Oil –
3. Calcium chloride (anhydrous)
4. Acid and salt -
A Water Rusting (medium amount)
B Boiled water + oil No rusting
C Calcium chloride (anhydrous) No rusting
D salt solution Rusting (large amount – salt is a catalyst)
E acid Rusting (large amount – acid is a catalyst)
• For iron to rust, it must be in contact with oxygen (air) and water.
iron + oxygen + water ____________________
• __________ and ___________ catalyse the reaction (make it faster)
Why is rusting a redox reaction?
The rusting of iron is a redox reaction
Higher 1. iron __________ electrons
How can rusting be prevented (stopped) ?
2. oxygen _________ electrons.
iron iron and tinned iron painted nail
The main way to stop rusting is to prevent water and/or oxygen from getting to the iron
(or steel). There are 6 methods you need to know about:
Method How does this method prevent rusting?
1 oil and grease
(particularly useful for moving parts e.g. wheels, engines, bicycle chains)
i.e. the more reactive metal is sacrificed to stop the iron from rusting
e.g. stainless steel is an alloy of iron that does not rust
6 tin plate
(so it will rust if scratched)
1. Set up the apparatus as shown above
2. Put a tick in the table below if you can see a change or a cross if there’s no change.
Zinc Magnesium Copper Lead
Order of Reactivity:
Most reactive metal:
Least reactive metal:
You should find there are 6 ticks (reactions). On the next page, write a word equation
(foundation level) or a symbol equation (higher level) for each one.
Word and Symbol Equations Foundation: finish the word equations
Higher: write symbol equations using the table underneath
to help you
magnesium + zinc nitrate +
magnesium + copper nitrate +
magnesium + lead nitrate +
zinc + copper nitrate +
zinc + lead nitrate +
copper + lead nitrate +
metal atoms metal ions non-metal ion
Mg Mg 2+
For your exam they want you to know the order of reactivity below:
Order of Reactivity:
Most Reactive: Magnesium Mg 1. LEARN this order of
Zinc Zn reactivity
Iron Fe 2. Be able to write word
Least Reactive: Tin Sn HIGHER – symbol equations too
• Redox reactions involve oxidation and reduction.
• Oxidation involves the __________ of electrons
• Reduction involves the __________ of electrons
• An oxidising agent ____________ electrons from something else causing it to be
oxidised i.e. the oxidising agent is being _____________
• A reducing agent _____________ electrons to something else causing it to be
reduced i.e. the reducing agent is being ___________.
e.g. Balanced equation:
Mg + CuSO4 Cu + MgSO4
Mg Mg2+ 2. Reducing agent
2. Oxidising agent
More Examples (specifically mentioned on your syllabus). They need completing
Cl2 2 Cl-
2 Cl- Cl2