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C6b Redox Reactions
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C6b Redox Reactions

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  • 1. C6b Redox Reactions Rusting is an example of a redox reaction. You studied Rusting in C2 but here is a reminder. What conditions are needed for rusting? 1. Boiled water – 2. Oil – 3. Calcium chloride (anhydrous) – 4. Acid and salt - Results Observations 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) Conclusion • For iron to rust, it must be in contact with oxygen (air) and water. iron + oxygen + water ____________________ RUST • __________ 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.
  • 2. corrosion indicator iron iron and tinned iron painted nail magnesium galvanised 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) 2 paint 3 galvanising 4 sacrificial protection i.e. the more reactive metal is sacrificed to stop the iron from rusting 5 alloying Topic C2 e.g. stainless steel is an alloy of iron that does not rust 6 tin plate (so it will rust if scratched)
  • 3. Displacement Reactions copper zinc lead magnesium zinc nitrate solution magnesium nitrate solution copper nitrate solution lead nitrate solution 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 Zinc nitrate solution Magnesium nitrate solution Copper nitrate solution Lead nitrate solution 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.
  • 4. 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+ NO3 - Zn Zn2+ Cu Cu2+ Pb Pb2+ For your exam they want you to know the order of reactivity below: Order of Reactivity: Important Most Reactive: Magnesium Mg 1. LEARN this order of Zinc Zn reactivity Iron Fe 2. Be able to write word equations Least Reactive: Tin Sn HIGHER – symbol equations too
  • 5. HIGHER ONLY • 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 ionic equation: Half-equations: 1. Oxidised Mg Mg2+ 2. Reducing agent 1. Reduced Cu2+ Cu 2. Oxidising agent More Examples (specifically mentioned on your syllabus). They need completing Fe Fe2+ Fe2+ Fe3+ Fe3+ Fe2+ Cl2 2 Cl- 2 Cl- Cl2