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Nancy Sharma , asked a question
Subject: Chemistry , asked on 17/5/12

In the standardization of Na2S2O3 using K2Cr2O7 by iodometry, the equivalent weight of
K2Cr207 is
(1) Molecular weight/2 (2) Molecular weight/6
(3) Molecular weight/3 (4) same as molecular weight


Kanika , Meritnation Expert added an answer, on 18/5/12

Dear Student,

The iodometry titration of K2Cr2O7, Chromium is being reduced by Na2S2O3 from Cr6+ in K2Cr2O7, to Cr3+, according to the following reaction :

Cr2O7 2- + 6 e- → 2 Cr3+

Now, since in this redox titration reduction of Chromium involves a 6 electron change, therefore the equivalent weight of K2Cr2O7 = Molecular weight / 6.

Thus, the correct option is (2).

Hope, this information is helpful.

Enjoy learning!!

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