Question

Calculate the oxidation number of sulphur, chromium and nitrogen in H₂SO₅,  Cr₂O₇^2- and  NO^3-

 Suggest structure of these compounds. Count for the fallacy. 

Answer 1

(i)    H₂⁺¹SO₃^-2

However, the O.N. of S cannot be +8. S has six valence electrons. Therefore, the O.N. of S cannot be more than +6. 

The structure of H₂SO₅ is shown as follows: 

Therefore, the O.N. of S is +6. 

(ii)    Cr₂O₇^2-

Here, there is no fallacy about the O.N. of Cr in  Cr₂O₇^2-

The structure of   Cr₂O₇^2-

is shown as follows: 

Here, each of the two Cr atoms exhibits the O.N. of +6. 

(iii)    NO₃^-

Here, there is no fallacy about the O.N. of N in NO₃^-

The structure of  NO₃^-

is shown as follows: The N atom exhibits the O.N. of +5.