The incorrect order is

Identify the element for which $+1$ oxidation state is more stable than $+3$ oxidation state.

Three allotropes $(A)$,$(B)$ and $(C)$ of phosphorus in the following change are respectively
$A \xrightarrow[1200 \ atm]{470 \ K} B$
$A \xrightarrow[CO_2 - atm]{570 \ K} C$

Which of the following mixtures of two gases in equimolar amounts will produce a blue liquid at $-30\,^oC$?

Which element is not present in Nessler's reagent?

Draw the structures of the following oxoacids of phosphorus:
$(i)$ Orthophosphoric acid $(H_{3}PO_{4})$
$(ii)$ Pyrophosphoric acid $(H_{4}P_{2}O_{7})$
$(iii)$ Orthophosphorus acid $(H_{3}PO_{3})$
$(iv)$ Hypophosphorus acid $(H_{3}PO_{2})$
$(v)$ Cyclotrimetaphosphoric acid $((HPO_{3})_{3})$
$(vi)$ Polymetaphosphoric acid $((HPO_{3})_{n})$