1. R edox by ycs

2. Why Redox? Combination of two processes Reduction Oxidation

3. Reduction What reduces you? Friends Parents Teachers????

4. Reduction In chemistry, terms associated with the reduction process are ‘OEHO!’ o xygen e lectrons h ydrogen o xidation state

5. Reduction L oss of oxygen G ain in hydrogen G ain of electrons D ecrease in oxidation state

6. Loss of Oxygen Fe 2 O 3 (s) + 3CO(g)  2Fe(s) + 3CO 2 (g) Which compound is reduced ? What is it reduced by ? termed as ‘reducing agent’

7. Gain in Hydrogen H 2 S(g) + Cl 2 (g)  2HCl(g) + S(s) Which compound is reduced ? What is it reduced by ? termed as ‘reducing agent’

8. Gain of Electrons Fe 2+ (aq) + 2e -  Fe(s) Why are the iron(II) ions reduced ?

9. Decrease in Oxidation State Fe 2+ (aq) + 2e -  Fe(s) Notice the state of iron changes ? From ………….to…………….? Decrease in oxidation state is REDUCTION

10. Oxidation Also associated with ‘OEHO!’ o xygen e lectrons h ydrogen o xidation state

11. Oxidation Reverse of Reduction Gain/loss of oxygen? Gain/loss of hydrogen? Gain/loss of electrons? Increase/decrease of oxidation state?

12. Agents R educing and O xidising agents Complicated affair

13. Reducing Agents Reducing agents REDUCES others but are themselves OXIDISED Examples are KI, CO, H 2 S, Metals.. Can you Name them?

14. Oxidising Agents Oxidising agents OXIDISES others but are themselves REDUCED Examples are FeCl 3, K 2 Cr 2 O 7, KMnO 4, H 2 O 2, O 2 Can you Name them?

15. Colour Changes Most of the agents undergo colour changes when they reduces or oxidises others…see your notes under Redox II for details..a MUST KNOW !

16. Colour Changes Oxidising agents – used to test for reducing agents e.g. Potassium permanganate : purple to colourless Potassium dichromate : orange to green Iron(III) chloride : yellow to green

17. Colour Changes Reducing agents – used to test for oxidising agents e.g. Potassium iodide : colourless to brown Sodium thiosulphate : changes iodine solution from brown to colourless

18. Activity Complete exercises in Redox I and II View this link for more informationlink