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The D-And-f-Block Elements

Question
CBSEENCH12007054

What is the oxidation state of chromium in (a) potassium dichromate, (b) potassium chromate?

Solution
Oxidation state of chromium in K2Cr2O7
oxidation state of K =1
oxidation state of O=(-2)
oxidation state of Cr= y
 
2 x1 +2 x y+(-2) x 7=0
2+2y-14=0
2+2y=14
2y=14-2
2y=12
y= 12/2
y=6

Oxidation state of chromium in K2CrO4
oxidation state of K =1
oxidation state of O=(-2)
oxidation state of Cr= y
2 x1+y+(-2) x4 =0
2 +y-8 =0
2+y=8
y=8-2
y=6

In both; K2Cr2O7 and K2CrO4, Cr is in +6 oxidation state.