redox indicator

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Offline Barrylkj

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redox indicator
« on: 01/08/2004 13:23:13 »
What is a redox indicator, and how does it work?


Offline starburst

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Re: redox indicator
« Reply #1 on: 01/08/2004 16:33:23 »
i tried looking them up on the net, but couldn't find any info on i probably guess that u mean these few... =S[?]

a redox indicator is an indicator that changes colour in the presence of an oxidising or reducing agent

examples of redox indicators...

acidified potassium dichromate (VI)

-changes frm orange to green in the presence of a reducing agent
-used to test for presence of a reducing agent
-dichromate (VI) ion, Cr2O7- is reduced to chromium (III) ion, cr3+

aqueous potassium iodide (KI)

-used to test for presence of an oxidising agent
-a drop of KI added to a solution containing an oxidising agent, brown solution formed. iodide ion (I-) is colourless, but aqueous iodine is brown. solution turns brown due to iodine produced
-starch iodide paper can also be used
--> oxidising agents change the colour of moist starch iodide paper frm white to blue
--> iodine reacts with starch to give a blue solution

acidified potassium manganate (VII)
-used to test for reducing agents
-changes frm purple to colourless i.e is decolourised
-MnO4- ion is reduced to MnO4 + (? not sure abt this =/)

that's all i can remember or plagiarise frm my o level pure chem textbk :D hehe...damn to think that i can't even remember all this stuff...better start revising my chem...prelim exams for the o levels are in 4 wks time! >_< argh feeling stressed out
« Last Edit: 01/08/2004 16:36:06 by starburst »