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Why is starch used as indicator in titration of iodine with sodium thiosulfate?
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Why is starch solution used as indicator in Sodium thiosulphate Iodine titrations instead of phenolphthalein indicator?
Phenolphthalein is an acid base indicator - it does not show the end-point in a thiosulfate type titration. Starch gives a very sharp end-point from a blue-black to colorless end-point when titrating iodine with thiosulfate. Phenolphthalein would just not detect this change.
What is iodometric titration?
In this titration iodine is liberated ....Added:... from (excess of) iodide by an oxidant. The Iodine is then titrated with thio (di-sodium thio-sulfate) and starch as indicator added just before the expected equivalence point.
Why potassium thiocyanate is added in the titration of sodium thiosulphate with copper?
On addition of the KI to your copper (II) solution, you formed Copper (I) iodine solid and produced the tri-iodide ion. It is the tri-iodide ion that you are titrating with the sodium thiosulfate. The tri-iodine ion is what itercalates into the starch molecules to form the dark blue color you are using as an end point in the titration. Some the the tri-iodide ion formed will adsorb to the surface of the solid copper (I) iodine formed. This must be desorbed for a complete titration. The addition of the potassium thiocyanate, displaces the adsorbed tri-iodine ion, and liberates it for titration.
Why is phenolphthalein indicator used in the titration of oxalic acid against sodium hydroxide?
Yes. Phenolphthalein can be used as an indicator for the titration of a weak acid (oxalic acid) against strong base (sodium hydroxide).
What are the three components in order of administration used to treat cyanide exposure?
Amyl nitrite, sodium nitrite, sodium thiosulfate
Why is starch solution used as indicator in Sodium thiosulphate Iodine titrations instead of phenolphthalein indicator?
Phenolphthalein is an acid base indicator - it does not show the end-point in a thiosulfate type titration. Starch gives a very sharp end-point from a blue-black to colorless end-point when titrating iodine with thiosulfate. Phenolphthalein would just not detect this change.
What are the steps of the winkler method in order?
Winkler Method is a classical method(titration method) for determine the dissolved oxygen(BOD).
Difference between iodometry and iodimetry?
When an analyte that is a reducing agent is titrated directly with a standard iodine solution, the method is called "iodimetry". When an analyte that is an oxidizing agent is added to excess iodide to produce iodine, and the iodine produced is determined by titration with sodium thiosulfate, the method is called "iodometry".
What is iodometric titration?
In this titration iodine is liberated ....Added:... from (excess of) iodide by an oxidant. The Iodine is then titrated with thio (di-sodium thio-sulfate) and starch as indicator added just before the expected equivalence point.
Why KI is added in redox iodometric titration even in the presence of sodium thiosulfate as a reducing agent?
In iodometric titrations sodium thiosulfate is the titrant whereas the KI will reduce the analyte; eg: Cu2+ to Cu+. The I2 produced is then titrated by the sodium thiosulphate. Cu2+ + I- --> CuI + I3- I3- + 2 S2O32- ¾® 3 I- + S4O62- To answer your question: KI (reducing agent) is added to generate the iodine by the reduction of the analyte (Cu2+) The formed iodine is then back-titrated with thiosulfate (titrant) to determine the amount of analyte originally present. As you can see the KI and sodium thiosulfate serve two different purposes. KI improves solubility of Iodine
Why potassium thiocyanate is added in the titration of sodium thiosulphate with copper?
On addition of the KI to your copper (II) solution, you formed Copper (I) iodine solid and produced the tri-iodide ion. It is the tri-iodide ion that you are titrating with the sodium thiosulfate. The tri-iodine ion is what itercalates into the starch molecules to form the dark blue color you are using as an end point in the titration. Some the the tri-iodide ion formed will adsorb to the surface of the solid copper (I) iodine formed. This must be desorbed for a complete titration. The addition of the potassium thiocyanate, displaces the adsorbed tri-iodine ion, and liberates it for titration.
Why is phenolphthalein indicator used in the titration of oxalic acid against sodium hydroxide?
Yes. Phenolphthalein can be used as an indicator for the titration of a weak acid (oxalic acid) against strong base (sodium hydroxide).
What is the balanced equation of fluorine reacts with sodium iodide?
2Na2S2O3 + I2 --> 2NaI + Na2S4O6
Redox titration iodometry?
If you're asking me to explain how Thiosulfate-Iodine titration works, I'll explain. Usually, this titration is used to calculate the amount of Iodide ions produced in a previous reaction, in order find the concentration of the substance reacted in that reaction. For example, in an attempt to find the percentage of Copper in a coin, the coin is first dissolved in concentrated Nitric acid, where Cu2+ ions are formed. Next, this solution is treated with excess Potassium Iodide solution. The reaction is: 2Cu2+ + 4I- ----> 2CuI + I2 The amount of Iodine liberated is then titrated with a known concentration of Sodium Thiosulfate solution. The reaction is: 2S2O32- + I2 ----> S4O62- + 2I-. Starch is used as indicator for this titration. The color at the end-point is bluish-black. From the volume of Thiosulfate required, the amount of Iodide ions can be calculated(using the second equation). From this, the amount of Copper can be calculated from the first equation. I hope this answers your question.
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 are the three components in order of administration used to treat cyanide exposure?
Amyl nitrite, sodium nitrite, sodium thiosulfate
What is the procedure for the standardization of sodium thiosulfate?
Thiosulfate can be standardised by adding excess potassium iodide solution to a known volume of a standard acidified solution of potassium dichromate, and then titrating the liberated iodine against the sodium thiosulfate solution.http://www.meduniv.lviv.ua/files/kafedry/tokshim/English/Analytical/Manuals_Analytchem/Iodometry.pdf
