In which substance oxidation number of oxygen is -1 ?

1.	In which substance oxidation number of oxygen is -1 ?
Answer» `KO_(2)` `HO_(2)^(-)` `H_(3)O^(+)` `OF_(2)` SOLUTION :`HO_(2)^(-)RARR(+1)+2(X)=-1` `therefore2x=-2" "thereforex=-1`

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