Which from following lanthanoids exhibits +4 oxidation state in $\mathrm{F}^7$ configuration?

Which among the following salts turns red litmus blue in its aqueous solution?

A container consisting mixture of $28 \mathrm{~g} \mathrm{~N}_2, 8 \mathrm{~g} \mathrm{He}$ and 40 g Ne at $25^{\circ} \mathrm{C}$. If the total pressure exerted by the gaseous mixture is 20 bar , What is the partial pressure exerted by $\mathrm{N}_2$ ?

Select the incorrect statement about $\mathrm{N}_2$ molecule.