Oxidation and Reduction - What are they?

1. REDOX REACTIONS Oxidation and Reduction

6. What is oxidation? A substance is oxidised if one the following happens after a reaction: It gains oxygen or It loses hydrogen or It loses electrons or It increases its oxidation state.

7. Oxidation — Gain of Oxygen 2Ca(s) + O 2 (g)  CaO(s) By the end of the reaction, calcium has gained oxygen. Calcium has been oxidised to calcium oxide . This process is called oxidation .

8. Oxidation — Gain of Oxygen CH 4 (g) + 2O 2 (g)  CO 2 (g) + 2H 2 O( l ) The carbon atom in methane has gained oxygen and has been oxidised to carbon dioxide . The hydrogen atom in methane has also gained oxygen . Hydrogen has been oxidised to water.

9. Oxidation — Loss of Hydrogen A substance is oxidised if it loses hydrogen. 2NH 3 (g) + 3CuO(s)  N 2 (g) + 3Cu(s) + 2H 2 O(g) Ammonia has lost hydrogen. It has been oxidised to nitrogen.

13. Oxidation — Increase in Oxidation State The oxidation state is the “ charge ” an atom of an element would have if it existed as an ion in a compound (even if it is actually covalently bonded). The oxidation state is also known as oxidation number .

14. Various Definitions of Oxidation & Reduction Redox Oxidation Reduction Gain in Oxygen Loss in Hydrogen Loss in Electron (s) Loss in Oxygen Gain in Hydrogen Gain in Electron (s ) Increase in Oxidation State Decrease in Oxidation State 1 2 3 4

15. Mnemonics for Redox – OIL - RIG OIL - RIG : Oxidation is Loss – Reduction is Gain Redox Oxidation Reduction Gain in Oxygen Loss in Hydrogen Loss in Electron (s) Loss in Oxygen Gain in Hydrogen Gain in Electron (s )

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