about f.6 chp.3 chemical equations and stoichiometry thz
in this chapter
titrations involving idine which is a mild oxidizing agent are offen called
starch solutionis is used indicator to signal the end point of the titration
when the brown colour of iodine fades as the end point approaches, a little
amout of starch solution is added.
the Q is
why don't we added the starch solution in the iodine solution,,and need to
added it when the brown colour of iodine change to pale yellow??
please explain it longer and use english
- 1 十年前最愛解答
The starch solution is act as the indicator.At the end point it is difficult to obserb when the colour change from pale yellow to colourless.SO starch solution is adder which clearly show the end point from dark blue to colourless.because starch can form a bule complex with iodine.
it is need added it when the brown colour of iodine change to pale yellow because when the concentration of iodine is high. the starch will form an irreversible blue complex with iodine.no iodine can release form the complex.so it must be added when the iodine containing solution when it is pale yellow (the concentation of iodine is low)