# 8.5 Calculate the oxidation number of sulphur, chromium, and nitrogen in  $H_{2}SO_{5}$, $Cr_{2}O_{7}^{2-}$and $NO_{3}^{-}$ . Suggest the structure of these compounds. Count for the fallacy.

(i)$H_{2}SO_{5}$  let the oxidation number of sulphur be x

So,

$\\2*1+x+5(-2)= 0\\ x= +8$

There is a fallacy Sulphur cannot have +8 oxidation state because it has maximum +6 oxidation number, not more than that.The structure of $H_{2}SO_{5}$ is shown as follows:

$2(H)+1(S)+3(O)+2(O \:\:in \:peroxy\: linkage)$

$\Rightarrow 2(+1) + 1(x) + 3(-2) + 2(-1) = 0$

$\Rightarrow x = +6( Answer))$

(ii) $Cr_{2}O_{7}^{2-}$

let the oxidation number of chromium be x

now

$\\2x+7*(-2)=-2\\ x= (-2+14)/2\\ x= +6$

There is no fallacy here

(iii) $NO_{3}^{-}$

let assume oxidation number of N is x

Now, $\\x+(-2)*3= -1\\(x-6)=-1\\x= +5$

here is  no fallacy about the O.N of N in $NO_{3}^{-}$

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