Determine the oxidation number of chromium in potassium dichromate, K2Cr2O7.

2+x−14=0

−12+x=0

x=12

Explanation:

assium exhibits an oxidation state of +1, oxygen exhibits an oxidation state of -2

So, the total charge of potassium ions is +1(2)=+2, while oxygen ions is −2(7)=−14.

Let x be the oxidation number of two chromiums.

Hence we can write the equation as

2+x−14=0

−12+x=0

x=12

So, two chromium atoms have an oxidation number of +12.

So one chromium atom will have an oxidation number of +12 /2=+6.

So oxidation number of Cr in K2Cr2O7 is +6.