NEET Solved Paper 2014 Question 25
Question: In acidic medium, $ H _2O _2 $ changes $ Cr _2O_7^{2-} $ to $ CrO _5 $ which has two (-O-O-) bonds. Oxidation state of Cr in $ CrO _5 $ is [AIPMT 2014]
Options:
A) +5
B) +3
C) 4-6
D) -10
Show Answer
Answer:
Correct Answer: C
Solution:
When $ H _2O _2 $ is added to an acidified solution of a dichromate, $ Cr _2O_7^{2-} $ ,
a deep blue coloured complex, chromic peroxide, $ CrO _5 $ $ [or,CrO,{{(O _2)}_2}] $ is formed.
$ Cr _2O_7^{2-}+2{H^{+}}+4H _2O _2\xrightarrow{,}\underset{Chromic,peroxide}{\mathop{2CrO{{(O _2)}_2}}},+5H _2O $
This deep blue coloured complex has the following structure Oxidation state of Cr is +6 due to the presence of two peroxide linkages,
which can be calculated as Cr peroxide normal $ x+(-1)4+(-2)=0 $ $ x-6=0 $ $ x=+6 $
