Of the following,the most acidic is

An orange solid $(X)$ on heating gives a colourless gas $(Y)$ and only a green residue $(Z)$. Gas $(Y)$ on treatment with $Mg$ produces a white solid substance. Identify the white solid substance.

Which of the following is $NOT$ true for $N_2O$?

What is the active species in Nessler's reagent used for the identification of ammonia?

When dilute $H_2SO_4$ is added to dry $KNO_3$,brown fumes are evolved. What are these brown fumes?

Which among the following oxides of nitrogen is a brown-coloured gas?