(i) S–S bond is present in H₂S₂O₆.

Therefore it can be clearly seen from the figure that there a bond between S-S.

(ii) In peroxosulphuric acid (H₂SO₅) sulphur is in +6 oxidation state.

Therefore the oxidation of S is +6 . to calculate the oxidation state of S. first consider it x

+1 + (-2) + x + (-2) + (-2) + (-1 + (-1) + 1 = 0

X = 6

(iii) In Haber’s process Fe and Mo is used as catalyst

(iv) Change in enthalpy is negative for the preparation of SO₃ by catalytic oxidation. The creation of sulphur dioxide is exothermic reaction.

Hence the correct options are (i) and (ii)