J. D. Lee Solutions for Chapter: Group 7 - the Manganese Group, Exercise 1: Exercise 1

When ammonium vanadate is heated with an oxalic acid solution, a compound $\left(\mathrm{Z}\right)$ is formed. A sample of $\left(\mathrm{Z}\right)$ was titrated with ${\mathrm{KMnO}}_4$ solution in hot acidic solution. The resulting liquid was reduced with ${\mathrm{SO}}_2,$ the excess ${\mathrm{SO}}_2$ boiled off, and the liquid again titrated with ${\mathrm{KMnO}}_4.$

The ratio of the volumes of ${\mathrm{KMnO}}_4$ used in the two titrations was $5:1.$ What conclusions can you make regarding the nature of the compound? $({\mathrm{KMnO}}_4$ oxidizes all oxidation states of vanadium to vanadium $(+\mathrm{V}). {\mathrm{SO}}_2$ reduces vanadium $(+\mathrm{V})$ $\left.(+\mathrm{IV}).\right)$ Find the oxidation state of vanadium in $\mathrm{Z}$.

How the last traces of dioxygen be removed from dinitrogen?

Manganese has been described as 'the most versatile element'. Explain this and show the similarities and differences between the chemistry of manganese and rhenium.

Explain why ${\left[\mathrm{Mn}({\mathrm{H}}_2\mathrm{O}{)}_6\right]}^{2+}$ is pale pink. ${\mathrm{MnO}}_2$ is black and ${\mathrm{MnO}}_4^{-}$ is intensely coloured purple.

Explain why a green solution of potassium manganate $\left(\mathrm{VI}\right)$ ${\mathrm{K}}_2{\mathrm{MnO}}_4$ turns purple and a brown solid is precipitated when carbon dioxide is bubbled into the solution.