Test: Oxidation Number (13 August) - JEE MCQ

OF₂ Fluorine is most electronegative atom with oxidation number = - 1
x - 2 = 0
x = + 2
H₂O₂   2 + 2x = 0 ⇒ x = - 1 

a) BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl is not a redox reaction, as there is no change in the oxidation state of any element.
It is an example of double displacement reactions.

Oxidation number of Cr changes from +6 to +3.

The correct answer is option A
(I) ^xPO₄³⁻​ ⇒ x + 4 × (−2) = −3
                ⇒x = −3 + 8 = +5
                ⇒x = +5
Oxidation number of P = +5
(II) ^xSO₄²⁻​ ⇒ x + 4 × (−2) = −2
                ⇒x = −2 + 8
                  ⇒x = +6
Oxidation number of S=+6
(III) ^xCr₂​O₇²⁻ ​    ⇒2x + 7 × (−2) = −2
                        ⇒2x =−2+14
                        ⇒2x=12
                        ⇒x= 12/2​ = +6

Fe²⁺ is added asFeSO₄
Fe⁺ is formed by charge transfer from NO to Fe²⁺ 



Fe⁺ has three unpaired electrons (N).

 The two sulfur atoms of thiosulfate exist in the oxidation state of sulfate (+6) and sulfide (−2) and do not change their respective oxidation states upon disproportionation.  

So difference in the oxidation states of two types of sulphur atoms will be

= (+6)- (-2) 

= +8