Question

In alkaline medium, thiosulphate ions are oxidised to sulphate ions by $Mn{O}_4^{-}$ ions. The oxidation number of $Mn$ decreases by ______ units.

Answer 1

Answer: 3

In alkaline medium,
$\underset{(+7)}{Mn{O}_4^{-}}\to \underset{(+4)}{Mn{O}_2}$
The oxidation number of $Mn$ decreases by $3$ units.