Which of the following is a use of alum?

Conc. $HNO_3$ can be stored in a container of

Write reactions to justify the amphoteric nature of aluminium.

Boron halides are Lewis acids because.....

Which of the following statements about $BF_4^{-}$ and $AlF_6^{3-}$ are correct?
$(i)$ $B$ and $Al$ differ in their oxidation states.
$(ii)$ $B$ and $Al$ differ in their covalency.
$(iii)$ $B$ obeys the octet rule.
$(iv)$ $B$ and $Al$ are in diagonal relationship.

Which element of group $13$ does not show the group valency in its compounds?