Write down the principle, procedure, calculation and chemical reaction for the estimation of Cu(II) ions iodometrically using Na2S2O3. The burette reading is 15.5 ml. Standard Na2S2O3 is N/10 N
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Answer:
In acid solution practically all oxidizing agents will oxidize iodide ion to iodine quantitatively. The iodine formed in the reaction can then be titrated by means of a standard sodium thiosulfate solution. This type of indirect titration is given the general name of iodometry. Iodometric methods of analysis have a wide applicability for the following reasons:
Potassium iodide, KI, is readily available in high purity.
A good indicator, starch, is available to signal the equivalence point in the reaction between iodine and thiosulfate. Starch turns blue-black in the presence of iodine. Therefore, when the blue-black color disappears, the iodine has been completely reduced to the iodide ion.
Iodometric reactions are rapid and quantitative.
A precise and stable reducing agent, sodium thiosulfate (Na2S2O3), is available to react with the iodine.
The amount of iodine liberated in the