Identify the correct statement from the following.
An inorganic compound $$\mathrm{W}$$ undergoes the following reactions:
$$ \begin{gathered} W+\frac{\mathrm{Na}_2 \mathrm{CO}_3}{\mathrm{O}_2 / \text { heat }} \rightarrow X+\frac{\mathrm{H}^{+}}{} \rightarrow Y_{(s)} \\ Y(a q)+\mathrm{KCl}(\mathrm{aq}) \rightarrow Z_{(S)} \end{gathered} $$
Z appears in the form of orange crystals and is used as an oxidising agent in acid medium. Identify the compound W.
The Lanthanoid ion which would form coloured compounds is -------------.
Atomic numbers: $$\mathrm{Yb}=70, \quad \mathrm{Lu}=71, \mathrm{Pr}=59, \quad \mathrm{La}=57$$
Arrange the following ions in the increasing order of their $$\Delta H_{(\text {hydration})}$$ values.
$$\mathrm{Cr}^{2+}, \mathrm{Co}^{2+}, \mathrm{Mn}^{2+}, \mathrm{Ni}^{2+}$$