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Why thiosulphate titration is called as redox titration?
A thiosulfate titration is mostly carried out to determine the amount of iodine present in the solution. In these reactions, thiosulfate ion acts as the reducing agent. This types titrations are often called as 'iodometric titrations'.
Why is starch used as indicator in titration of iodine with sodium thiosulfate?
Starch forms a blue-black complex with iodine, making it easy to see when the iodine has been fully neutralized in the titration. The color change is very distinct, allowing for accurate endpoint determination in the titration process.
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 does the blank titration use more ns2s2o3?
The blank titration requires more sodium thiosulfate (Na2S2O3) because it compensates for any residual iodine in the reaction mixture that didn't react with the analyte. This residual iodine can interfere with the accuracy of the titration results, so more Na2S2O3 is needed to completely neutralize it.
Why come again colour change after endpoint of titration of sodium thiosulphate with iodine?
The color change occurs because iodine reacts with starch to form a blue-black complex. Initially, the iodine reacts with the sodium thiosulfate until it is completely consumed, resulting in a color change from yellow to brown. Once the sodium thiosulfate is depleted, any excess iodine present reacts with the starch indicator, causing the solution to turn blue-black, indicating the endpoint of the titration.
Why thiosulphate titration is called as redox titration?
A thiosulfate titration is mostly carried out to determine the amount of iodine present in the solution. In these reactions, thiosulfate ion acts as the reducing agent. This types titrations are often called as 'iodometric titrations'.
Why is starch used as indicator in titration of iodine with sodium thiosulfate?
Starch forms a blue-black complex with iodine, making it easy to see when the iodine has been fully neutralized in the titration. The color change is very distinct, allowing for accurate endpoint determination in the titration process.
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 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 does the blank titration use more ns2s2o3?
The blank titration requires more sodium thiosulfate (Na2S2O3) because it compensates for any residual iodine in the reaction mixture that didn't react with the analyte. This residual iodine can interfere with the accuracy of the titration results, so more Na2S2O3 is needed to completely neutralize it.
Why come again colour change after endpoint of titration of sodium thiosulphate with iodine?
The color change occurs because iodine reacts with starch to form a blue-black complex. Initially, the iodine reacts with the sodium thiosulfate until it is completely consumed, resulting in a color change from yellow to brown. Once the sodium thiosulfate is depleted, any excess iodine present reacts with the starch indicator, causing the solution to turn blue-black, indicating the endpoint of the titration.
What is indirect titration?
In indirect titration, a substance that reacts with the analyte is added first, and then the excess of this substance is titrated with another reagent to determine the amount used. This method is useful when the analyte does not directly react with the titrant.
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".
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.
Why iodometic titration is better than iodimetric titration?
Iodometric titration is better than iodimetric titration for the determination of reducing agents, as it directly measures the amount of oxidizing agent present. This method is more precise, as it involves the direct reduction of a known quantity of iodine to iodide ion. It is also less prone to interference from side reactions compared to the indirect measurement in iodimetric titration.
Redox titration using sodium thiosulphate and potassium iodate?
In redox titration using sodium thiosulfate and potassium iodate, the iodate ion (IO3-) is reduced to iodine (I2) by thiosulfate ion (S2O32-). The iodine formed is then titrated with sodium thiosulfate until the endpoint is reached, indicated by a color change from yellow to colorless when all the iodine is reacted. This method is commonly used to determine the concentration of oxidizing agents in a sample.
What is the function of potassium iodide in iodometric titration?
Potassium iodide is used in iodometric titration as a source of iodide ions. It reacts with iodine to form triiodide ions, which are then titrated with a standard solution of thiosulfate to determine the concentration of the oxidizing agent.
