Chemistry - f-block Question with Solution | TestHub

All Lanthanoids give ${\mathrm{H}}_2$ when react with dil HCl .

Among ${\mathrm{Sm}}^{3\oplus },{\mathrm{La}}^{3\oplus },{\mathrm{Lu}}^{3\oplus }$ and ${\mathrm{Gd}}^{3\oplus }$ only ${\mathrm{Gd}}^{3\oplus }$ & ${\mathrm{Sm}}^{3\oplus }$ is coloured in aq soluton.

Nb and Ta have almost same size because in case of Ta due to poor shielding of 5 f subshell size decreases.

Cerium (IV) act as oxidizing agent and use as a good analytic reagent as a colourless solution of $\mathrm{Ce}{\left({\mathrm{SO}}_4\right)}_2$.