Oxidation number of osmium $(Os)$ in $OsO_4$ is

In thiosulphuric acid $(H_2S_2O_3)$,which of the following statements is correct?

The oxidation number of carbon in graphite is ....... .

Which ordering of compounds is according to the decreasing order of the oxidation state of nitrogen?

In acidic medium,$H_2O_2$ changes $Cr_2O_7^{2-}$ to $CrO_5$ which has two peroxy linkages. The oxidation state of $Cr$ in $CrO_5$ is

Assertion: In some cases,oxygen exhibits a positive oxidation state. Consequently,it is an electronegative element.
Reason: Fluorine is more electronegative than oxygen.