25mL of decimolar solution of a stable divalent transition metal cation is oxidised by 50mL of 0.02M acidified permanganate solution. What is the final oxidation state of the metal?

Explanation

5 moles of `M^(2+)` ion =x moles of permanganate , where x is the increase in oxidation number of the metal ion, `M^(2+)`
Using the molarity equation for the titration
`(V_(1)M_(1))/(5)=(V_(2)M_(2))/(x)`
The final oxidation state of metal `=+2-(-2)=+4`