Oxidation Number of Manganese in Alkaline Oxidative Fusion Product

Alkaline oxidative fusion of manganese dioxide ($\text{MnO}_2$) involves heating $\text{MnO}_2$ with an alkali metal hydroxide (such as $\text{KOH}$ or $\text{NaOH}$) in the presence of an oxidizing agent like atmospheric oxygen ($\text{O}_2$) or potassium nitrate ($\text{KNO}_3$).

The balanced chemical equation for the reaction is:
$2\text{MnO}_2 + 4\text{KOH} + \text{O}_2 \xrightarrow{\Delta} 2\text{K}_2\text{MnO}_4 + 2\text{H}_2\text{O}$

The manganese-containing product formed is potassium manganate, $\text{K}_2\text{MnO}_4$, which contains the manganate ion ($\text{MnO}_4^{2-}$).

To determine the oxidation state of $\text{Mn}$ in $\text{MnO}_4^{2-}$:
$\text{Oxidation state of Mn} + 4 \times (\text{Oxidation state of O}) = -2$
$x + 4(-2) = -2$
$x - 8 = -2 \implies x = +6$

Therefore, the oxidation number of $\text{Mn}$ in the product is $6$.