Describe the general chemical reactions of lanthanoids with the help of a diagram and state their uses.

(N/A) The general chemical reactions of lanthanoids $(Ln)$ are shown in the diagram below.
$(i)$ Lanthanoids are used in the production of alloy steels for plates and pipes.
$(ii)$ Mischmetall: It is a well-known alloy consisting of about $95 \%$ lanthanoid metal and about $5 \%$ iron,along with traces of $S, C, Ca,$ and $Al$.
Uses: $A$ large quantity of Mischmetall is used in $Mg$-based alloys. It is used to produce bullets,shells,and lighter flints.
$(iii)$ Uses of mixed oxides of lanthanoids: Mixed oxides are used as catalysts in petroleum cracking. Some lanthanoid oxides are used as phosphors in television screens and in fluorescent surfaces.