The salt which responds to dilute and concentrated $H_2SO_4$ is

Which of the following silver precipitates dissolves in $dil. \, HNO_3$ to produce a clear solution?

Which of the statement is incorrect for the given paragraph?
Simple salt $\xrightarrow{\text{Flame test}}$ Golden yellow flame
Simple salt $\xrightarrow[MnO_2]{Conc. H_2SO_4} (X)$ Yellowish green gas
Simple salt $\xrightarrow{AgNO_3} (Z)$ White ppt. (Insoluble in dil. $HNO_3$)
Simple salt $\xrightarrow[Conc. H_2SO_4]{K_2Cr_2O_7} (Y)$ Reddish brown vapour

When $BaCl_2$ is added to a clear solution of a compound $(X)$,a heavy white precipitate is formed which does not dissolve in $dil. HCl$. What is the compound $(X)$?

$A$ salt is heated first with dil. $H_2SO_4$ and then with conc. $H_2SO_4$. No reaction takes place. It may be

Select the correct match for the separation of anions using the given reagent.