$A$ $1 \ L$ flask is full of brown bromine vapour. The intensity of the brown colour of the vapour will not decrease appreciably on adding which of the following to the flask?

Which of the following is a neutral oxide?

The element $X$ which forms a stable product of the type $XCl_4$ is $....$

Which property of $CO_2$ makes it biologically and geo-chemically important?

Which one of the following elements will remain as liquid inside pure boiling water?

Identify the correct statements from the following.
$i$. Melting points and boiling points of group $13$ elements are much higher than those of corresponding group $14$ elements.
$ii$. $SiO$ only exists at high temperatures.
$iii$. $PbI_4$ does not exist.
$iv$. Buckminster fullerene contains twelve $6$-membered carbon rings and twenty $5$-membered carbon rings.