1.5 b Learning Outcomes apply knowledge of oxidation and reduction to explain the rusting of iron give an example of an oxidising and a reducing bleach carry out an experiment to show that halogens act as oxidising agents(reactions with bromides, iodides, Fe2+ and sulfites; half equations only required)

Rust Rust is the formation of iron oxides (usually red oxides), formed by the reaction of iron and oxygen in the presence of water / air moisture.

Swimming pools The water in swimming pools is kept sterile by the addition of oxidizing agents, chlorine or chlorine compounds, which kill microorganisms by oxidation. The active agent is usually chloric(1) acid (HOCl). It is usually put into the water as calcium hypochlorite Ca(OCl)2 The pH is kept low to keep the free chlorine concentration at a maximum. A colorimeter works on the principle that the Absorbance (colour) is proportional to the concentration of the free chlorine

Redox Experiments 3 of 7 Redox Experiments involve HalOgens Note: Focus on Oxidizing force (ability to be reduced or gain e- ). The halogens {Flourine, chlorine, bromine & Iodine) are lesser oxidizing agents as you go down the group because their electronegativity (Ox. Agents are reduced). Flourine is too dangerous to work with in the lab so only Cl2, Br2, I2 considered. Result: Less Reactive Oxidizing halogen is displaced

1. To Show Chlorine is a More Oxidizing Agent than Bromine Half Reactions: Oxidation: 2Br-  Br2 + 2e- Reduction: Cl2 + 2e-  2Cl- Br2 weaker Ox.Agent Method: Prepare test tube by washing with deionized water Fill one 1/4 of test tube with aqueous potassium bromide solution (sodium bromide can also be used) Add a 1/4 of a test tube of chlorine water Result: Colourless solution turns Orange (Formation of Br2) 

2. To Show Chlorine is a More Powerful Oxidizing than Iodine Half Reactions: Oxidation: 2I-  I2 + 2e- Reduction: Cl2 + 2e-  2Cl- Method: Prepare test tube by washing with deionized water Fill one 1/4 of test tube with aqueous potassium iodide solution Add a quarter of a test tube of chlorine water Result: Colourless solution turns brown (formation of I2)  I2 weaker Ox.Agent

3. To Show Bromine is a More Powerful Oxidizing than Iodine Half Reactions: Oxidation: 2I-  I2 + 2e- Reduction: Br2 + 2e-  2Cl- Method: Prepare test tube by washing with deionized water Fill 1/4of test tube with aqueous potassium iodide solution Add a 1/4 of a test tube of bromine water Result: Colourless solution turns Brown (Formation of I2 ) I2 weaker Ox.Agent

Redox Experiments Cont’d 1 of 7 Redox Experiments involve addition of O 1. Oxidizing the Sulfite Ion (SO32-) to the Sulfate Ion (SO42-) using the Halogens (SO32-) (SO42-)

Redox Practicals Cont’d 1 of 7 Redox Reactions involve Increase of Oxidation Number 1. Oxidizing the Fe2+ to Fe3+ using the Halogens Green Brown (Fe2+) (Fe3+)

2 of 7 Redox Reactions involve Displacement of Metals Redox Practicals Cont’d 2 of 7 Redox Reactions involve Displacement of Metals Note: Focus on Reducing force (ability to be Oxidised or lose e- ) of Metal. Displacement reactions occur when a metal from the electrochemical series is mixed with the ions of a metal lower down in the series. The atoms of the more reactive Reducing metal push their electrons on to ions of the less reactive metal. Result: Less Reactive Reducing Metal is displaced