Which of the following lanthanoids show $+2$ oxidation state besides the characteristic oxidation state $+3$?

An unknown inorganic compound $\left(\mathrm{X}\right)$ gave the following reactions:

$\left(\mathrm{i}\right)$ The compound $\left(\mathrm{X}\right)$ on heating gave a residue, oxygen and oxide of nitrogen.

$\left(\mathrm{ii}\right)$ An aqueous solution of the compound $\left(\mathrm{X}\right)$ on the addition of tap water gave turbidity, which did not dissolve in ${\mathrm{H}}_3{\mathrm{O}}^{+}$.

$\left(\mathrm{iii}\right)$ The turbidity dissolved in ${\mathrm{NH}}_4\mathrm{OH}$.

Identify the compound $\left(\mathrm{X}\right)$ and give the equations for the reactions $\left(\mathrm{i}\right), \left(\mathrm{ii}\right)$ and $\left(\mathrm{iii}\right)$.

An inorganic compound silver nitrate (X) gave the following reactions:

An aqueous solution of compound (X) on addition to tap water have a turbidity which did not dissolve in ${\mathrm{HNO}}_3$

Give equations for the reactions.

An unknown inorganic compound $\left(\mathrm{X}\right)$ gave the following reactions:

$\left(\mathrm{i}\right)$ The compound $\left(\mathrm{X}\right)$ on heating gave a residue, oxygen and oxide of nitrogen.

$\left(\mathrm{ii}\right)$ An aqueous solution of compound $\left(\mathrm{X}\right)$ on the addition of tap water gave turbidity, which did not dissolve in ${\mathrm{H}}_3{\mathrm{O}}^{+}$.

$\left(\mathrm{iii}\right)$ The turbidity dissolved in ${\mathrm{NH}}_4\mathrm{OH}$.

Identify the compound $\left(\mathrm{X}\right)$ and give the equations for the reactions $\left(\mathrm{i}\right), \left(\mathrm{ii}\right)$ and $\left(\mathrm{iii}\right)$.

An aqueous solution of an inorganic compound $\left(\mathrm{X}\right)$ gives the following reactions:

$\left(\mathrm{i}\right)$ With the aqueous solution of barium chloride, a precipitate insoluble in dilute $\mathrm{HCl}$ is obtained.

$\left(\mathrm{ii}\right)$ The addition of excess $\mathrm{KI}$ gives a brown precipitate, which turns white on the addition of an excess of hypo.

$\left(\mathrm{iii}\right)$ With an aqueous solution of ${\mathrm{K}}_4\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6\right]$, a chocolate-coloured precipitate is obtained.

Identify the compound $\left(\mathrm{X}\right)$ and give the equations for the reactions $\left(\mathrm{i}\right), \left(\mathrm{ii}\right)$ and $\left(\mathrm{iii}\right)$.

An aqueous solution of the inorganic compound $\left(\mathrm{X}\right)$ gives the following reactions:

Addition of an excess of $\mathrm{KI}$ gives a brown ppt. Which turns white on the addition of an excess of hypo

Identify the compound $\left(\mathrm{X}\right)$ and give equations for the reactions $\left(\mathrm{i}\right), \left(\mathrm{ii}\right) \text{and} \left(\mathrm{iii}\right)$.

An aqueous solution of inorganic compound containing${\mathrm{Cu}}^{+2} \mathrm{ion}$  (X) gives following reactions:

With an aqueous solution of ${\mathrm{K}}_4\mathrm{Fe}(\mathrm{CN}{)}_6$ chocolate coloured precipitate is obtained.

Give equation for the reaction.