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Redox Titration

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Report of redox titration---
Iodine titrated against sodium thiosulphate
Objectives
The objective of this experiment is to balance the equation for the reaction between sodium thiosulphate and iodine.
Principle
As the reaction between sodium thiosulphate and iodine is a redox reaction, so I make use of this to perform a redox titration, iodine titrated against sodium thiosulphate. From the experimental result, I can find out the number of mole of the two substances, hence I can calculate the mole ratio of the two substances. After find out the mole ratio, I can balance the equation of the reaction.

And the indicator use in this experiment is starch solution, which is dark blue in colour in the presence of iodine. The disappearance of the dark blue colour is the end point of the titration. Results

|Weight of Na2S2O3 |3.00g | | |Trial |1 |2 |3 | |Final b r | | | | | |I reading | | | | | |Volume used/ | | | | | |Mean vol. | | | | |

Calculation
1.
2.
Discussion
From the results, the ratio of Na to Iodine is 2:1, and the balanced equation is _____. Iodine is the limiting agent; all the Iodine has form sodium iodide and the remaining Na has form ______.
As iodine will react with starch solution to form a dark blue colour, so I use sodium thiosulphate titrate iodine, which have a sharply change to indicator the end point. But if the starch solution added to soon, the compound formed from iodine and starch will have a compress because of stable, and I mat get...

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