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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: lingo_belle on April 10, 2008, 02:15:45 AM

Title: titration between Na2S2O5 and KMnO4
Post by: lingo_belle on April 10, 2008, 02:15:45 AM

Hi all,


I'm trying to do a titration between Na2S2O5 and KMnO4 with the latter as the titrant. Pardon me if i'm wrong, the former - a reducing agent and latter as oxidising agent, redox reaction should occured?

What I'm trying to do, is to check for COD presence in Na2S2O5 using a test method given by my counterparts.
I prepared a 100ppm of Na2S2O5, taking 100ml of it into a conical flask, added with 98% H2SO4 and supposedly add in 10ml of my titrant. Accordingly, I should observe a color change from colorless to purple( caused by addition of KMnO4) and put in water bath for 30min.

However, I could not see any color change at all, thus unable to carry out the titration. Any reason for tat? Kindly advise!

I apologise for any confusion caused. Let me know if more information is needed.

Thx all

belle

Title: Re: titration between Na2S2O5 and KMnO4
Post by: AWK on April 10, 2008, 02:53:07 AM

You used the excess of KMnO4 or you use a different compound than Na2S2O5
Start from a balanced reaction!