AS4U required 29.98 ml. df 0.03 mL of MnO, was required to produce enou of the p

Question

AS4U required 29.98 ml. df 0.03 mL of MnO, was required to produce enou of the permanganate solution r of unreacted Mn04 to appearh 6 required 20 lution for the faint color of unreacted Mno cess KMnO, solution for the faint color of unreacted 0-g a blank titration, 0.03 mL of MnO4 was Iculate the molarity of the permanganate solu color to be seen. Calculate the molarity of the pemar NO3 was in, Methods Involving Iodine 15-22. Why is iodine almost always used in a solution containg is iodine almost always used in a solution containin 15-22. Why excess I? 15-23. State two ways to make standard triiodide solution. tor not added until just before the end point? Why? 15-25. (a) Potassium iodate solution was prepared by dissolving 50.00 mL of the solution were pipetted into a flask and treated with 15-24. In which technique, iodimetry or iodometry, is starch indica- 1.022 g of KIO3 (FM 214.00) in a 500-mL volumetric flask. The excess KI (2 g) and acid (10 mL of 0.5 M H SO4). How many moles o of I3 are created by the reaction?

Explanation / Answer

If a standard iodine solution is used as a titrant for an oxidizable analyte, the technique is iodimetry. If an excess of iodide is used to quantitatively reduce a chemical species while simultaneously forming iodine, and if the iodine is subsequently titrated with thiosulfate, the technique is iodometry. Iodometry is an example of an indirect determination since a product of a preliminary reaction is titrated.

The use of iodine as a titrant suffers from two major disadvantages. First, iodine is not particularly soluble in water, and second, iodine is somewhat volatile. Consequently, there is an escape of significant amounts of dissolved iodine from the solution. Both of these disadvantages are overcome by adding iodide (I– ) to iodine (I2) solutions. In the presence of iodide, iodine reacts to form triiodide (I3 – ) which is highly soluble and not volatile.

  concentrated solutions are violet. Iodide solutions are colorless. If all of the other solution components are colorless, it is possible to detect the endpoint of titrations involving triiodide without the use of an indicator. Endpoint detection is considerably easier, however, with an indicator. The indicator that is usually chosen for titrations involving iodine (triiodide) is starch. Starch forms a dark blue complex with iodine. The end point in iodimetry corresponds to a sudden color change to blue. Likewise the end point in iodometry corresponds to a sudden loss of blue color due to the complex. Potato starch, rather than corn starch, is preferred for making the indicator solution since the color change due to the starch complex at the end point is sharper. In iodometry the starch is added only after the color due to triiodide has begun to fade, i.e., near the endpoint, because starch can be destroyed in the presence of excess triiodide.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.