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Redox Reactions.

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Introduction

Redox Reactions. AIM In this practical suitable reactions will be carried out in an attempt to place a number of oxidising agents in order of oxidising strength. The oxidising agents are reduced according to the following redox half equations: A. B. C. D. E. F. EXPERIMENTS Experiment 1 Consider the two oxidising agents iodine, I2, and iron (III) ions, Fe3+. Their reduction can be represented as follows: Add a little of a solution of iron (III) ions to a solution of iodide ions. Observation: When the yellowy-orange solution of Fe3+ ions was added to a colourless solution of iodide ions the solution darkened to a brown colour. Addition of a few drops of starch (colourless in appearance), turned the mixture blacky/blue indicating that iodine is present. Ionic Equation For This Reaction: Inference: Since the Fe3+ has oxidised the 2I- to I2 then the order of oxidising strength is: Fe3+ > I2 Experiment 2 Consider the two oxidising agents chlorate ions, ClO-, and iron (III) ...read more.

Middle

solution was added to the colourless solution of bromide ions, there was no change in appearance so the mixture was colourless. Ionic Equation For This Reaction: Inference: Had bromine molecules been formed, an orange/red precipitate would have formed. Therefore, since there was no reaction this suggests that ClO- ions could not oxidise the Br- to Br2, so the order of oxidising strength is: Br2 > ClO- Experiment 4 Consider the two oxidising agents chlorate ions, SO42-, and iodine, I2. Their reduction can be represented as follows: Add a little of a saturated solution of sulphur dioxide (this contains sulphuric (IV) acid) to a solution containing iodine. Observation: When the colourless solution of sulphur dioxide was added to a pale yellow/orange solution of I2 the solution quickly decolourised. Ionic Equation For This Reaction: Inference: The change in colour implies that iodine ions were formed. ...read more.

Conclusion

(Experiment 6) Acidified manganate (VII), MnO4-, is reduced according to the redox half equation: Firstly, MnO4- should be compared with the strongest oxidising agent on the list above - Cl2 - whose reduction can be represented as: Add a solution of chloride ions to acidified manganate (VII) [ this is produced by adding some dilute sulphuric acid to potassium manganate (VII) solution]. Observation: When the colourless chloride ion solution was added to the purple solution of acidified manganate (VII), the mixture turned colourless. Ionic Equation For This Reaction: Inference: Since the MnO4- has oxidised the Cl- to Cl2 then the order of oxidising strength is: MnO4- > Cl2 This means that the addition of MnO4- to the experimental data changes the list to: MnO4- > Cl2 > Br2 > ClO- > Fe3+ > I2 > SO42- ?? ?? ?? ?? 1 ...read more.

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