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1. Firstly wash out a burette twice with distilled water.
2. Clean the washed burette with the approximately 0.1 mol dm-3 standardised sodium thiosulphate, which is going to be prepared.
3. Fill the burette with approximately 0.1 mol dm-3 standardised sodium thiosulphate, until the bottom of the meniscus is at the 0 cm3 mark on the burette.
4. Pipette 25cm3 of 0.020 mol dm-3 potassium Iodate solution into a 250 cm3 conical flask.
5. Using a 10cm3 measuring cylinder, measure out 10cm3 of 0.5 mol dm-3 potassium iodide and add it to the conical flask.
6. Using a 10cm3 measuring cylinder, measure out 10cm3of 1 mol dm-3 sulphuric acid and add it to the conical flask.
At this stage the three solutions will be mixed together in the conical flask, to produce iodine.
7. Record the initial reading on the burette (0 cm3) to work out the titre, record this to two decimal places
8. Turn the burette tap, so the 0.1 mol dm-3 sodium thiosulphate pours into the iodine in the conical flask (adding small amounts and then stirring the conical flask)
9. When the red/brown iodine solution in the flask turns yellow, stop titrating the 0.1 mol dm-3 sodium thiosulphate into the flask
10. Add a few drops of the starch indicator to the conical flask; it will turn dark blue/black colour to intensify the colour change.
11. Turn the burette tap back on, add the 0.1 mol dm-3 sodium thiosulphate drop wise, whilst swirling the flask, until the dark blue/black colour disappears.
12. Record the final burette reading, from the point where the bottom of the meniscus is.
13. Record the result in the table, and then calculate the titre value by finding the difference between the initial reading and the final reading.
14. Repeat the titration to obtain concordant results, whereby the titre is 0.1 cm3 difference at max.
15. Obtain all your results and present them in a table, to two decimal places.
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∙ 13y ago
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∙ 13y agowhat is the procedure of standardization of Sodium thiosulphate (0.025N)with potassum dichromate (0.25N)
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∙ 12y agoadd 25g of sodiun thiosulphate to 1litre of water of water to make it o.1N solution. Make it 0.01 by 1:10 dilution.
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∙ 6y agoIt is impossible to do correct chemical experiments or chemical analysis with substances having an unknown concentration.
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∙ 15y agousing potassiumdichromate
Ravi Bhandare
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Why do you use starch to standardise sodium thiosulphate using potassium iodate?
The iodine produced from the KIO3 reacts with the starch to produce the blue black colour used as the indicator
Equation between potassium iodate and sodium thiosulphate?
This reaction may be misunderstood as a direct reaction between the thiosulphate and iodate ions , however, in practice an iodide and acid mediated production of iodine from the iodate is used to react with the thiosulphate. A standard reaction used to calibrate a solution of sodium thiosulphate is as follows: Acid and potassium iodide are added to a solution of potassium iodate getting the following reaction: KIO3 + 5KI + 3H2SO4 = 3I2 + 3K2SO4 + 3H2O represented by the following ionic equation: IO3- + 5I- + 6H+ = 3I2 + 3H2O Thiosulpathe is titrated against this solution (effectively against iodine): I2 + 2Na2S2O3 = Na2S4O6 + 2NaI represented by the following ionic equation: I2 + 2S2O32- = S4O62- + 2I- where the dark brown coloured solution of iodine turns pale yellow and finally colourless as the reaction proceeds (starch is used as indicator after the pale yellow transition forming a black solution due to an iodine-starch complex which turns colourless upon further addition of thiosulphate).
What is the use of Sodium thiosulphate in iodometry?
In iodometry sodium thiosulphate is used because it is standardized by potassium dichromate and it is the best and relaible way to standardized sodium thiosulphate using iodometric titration. Infact sodium thiosulphate is also standardized by iodimetry. The difference between both of them is only of iodine. In iodometry iodine gas is liberated that will further react with sodium thiosulphate but in iodimetry standard solution of iodine is used.
Why sodium thiosulphate is called hypo?
Because it used to be called Sodium hyposulphite.
Why is sodium thiosulphate stored in a brown bottle?
Because it is :)
Indicator used during the standardization of sodium thiosulphate?
Starch
Why do you use starch to standardise sodium thiosulphate using potassium iodate?
The iodine produced from the KIO3 reacts with the starch to produce the blue black colour used as the indicator
Redox titration using sodium thiosulphate and potassium iodate?
(1) io3- + 5i- + 6h+ ® 3i2 + 3h2o (2) i2 + 2s2o32- ® 2i- + s4o62-
Methods of producing iodized salt?
Iodine is added to salt as potassium (sodium) iodide or potassium (sodium) iodate. An iodine deficiency is a source of thyroide diseases or can lead to idiocy.
Is iodized salt is a mixture of potassium iodide and common salt?
Almost yes, but it may sometimes contain Potassium iodate, Sodium iodate or Sodium iodide in place of Potassium iodide
How does potassium and sodium thiosulphate turn yellow?
No, it can turn it green.
Equation between potassium iodate and sodium thiosulphate?
This reaction may be misunderstood as a direct reaction between the thiosulphate and iodate ions , however, in practice an iodide and acid mediated production of iodine from the iodate is used to react with the thiosulphate. A standard reaction used to calibrate a solution of sodium thiosulphate is as follows: Acid and potassium iodide are added to a solution of potassium iodate getting the following reaction: KIO3 + 5KI + 3H2SO4 = 3I2 + 3K2SO4 + 3H2O represented by the following ionic equation: IO3- + 5I- + 6H+ = 3I2 + 3H2O Thiosulpathe is titrated against this solution (effectively against iodine): I2 + 2Na2S2O3 = Na2S4O6 + 2NaI represented by the following ionic equation: I2 + 2S2O32- = S4O62- + 2I- where the dark brown coloured solution of iodine turns pale yellow and finally colourless as the reaction proceeds (starch is used as indicator after the pale yellow transition forming a black solution due to an iodine-starch complex which turns colourless upon further addition of thiosulphate).
How many moles of Na2S2O3 react with one mole of KClO3 used in the standardization?
Standardization of sodium thiosulfate uses potassium iodate with excess potassium iodide and acidified. Iodine is liberated and that is titrated with sodium thiosulfate. KIO3 + 5KI + 3H2SO4 -----> 3K2SO4 + 3H2O + 3 I2 I2 + 2Na2S2O3 -------> 2NaI + Na2S4O6 So 1 mole of KIO3 produces 3 moles of Iodine. 1 moles of iodine reacts with 2 moles of thiosulfate. So 6 moles of sodium thiosulfate react with 1 mole of potassium iodate KIO3.
What is the chemical equation for the iodization of salts?
Iodine in the iodized salt exist as iodine salts (potassium iodide/iodate or sodium iodide/iodate).These salts are dissolved and dissociated in the organism as NaCl.
What is the use of Sodium thiosulphate in iodometry?
In iodometry sodium thiosulphate is used because it is standardized by potassium dichromate and it is the best and relaible way to standardized sodium thiosulphate using iodometric titration. Infact sodium thiosulphate is also standardized by iodimetry. The difference between both of them is only of iodine. In iodometry iodine gas is liberated that will further react with sodium thiosulphate but in iodimetry standard solution of iodine is used.
Formula for sodium iodate?
Sodium iodate is NaIO3.
What ingredients are used in iodised salt?
Generally used are potassium iodide or iodate; rarely used sodium iodide or iodate. Also added is an anticaking agent.
