Which of the following oxides is not expected to react with sodium hydroxide?

Which of the following metals displaces $SO_2$ gas from concentrated sulphuric acid?

The white precipitate $(Y)$, obtained on passing a colourless and odourless gas $(X)$ through an ammoniacal solution of $NaCl$, loses about $37 \%$ of its weight on heating and a white residue $(Z)$ of basic nature is left. Identify $(X)$, $(Y)$, and $(Z)$ from the following sets.

When $Mg$ burns in air,it produces

The correct order of increasing ionic character among $LiH$,$NaH$,$KH$,$RbH$,$CsH$ is

$NO_2$ is not obtained on heating: