Which of the following halides react$(s)$ with $AgNO_{3(aq)}$ to give a precipitate that dissolves in $Na_2S_2O_{3(aq)}$?
$A$. $HCl$
$B$. $HF$
$C$. $HBr$
$D$. $HI$

Assign $A, B, C, D$ from the given type of reaction.
$BaSO_4 \downarrow + dil. HCl$ $(Excess)$ $\longrightarrow$ No reaction

$A$ white sodium salt dissolves readily in water to give a solution which is neutral to litmus. When silver nitrate solution is added to the solution,a white precipitate is formed which does not dissolve in dilute nitric acid. The anion could be

$[X] + H_2SO_4 \to [Y]$ (a colourless gas with irritating smell).
$[Y] + K_2Cr_2O_7 + H_2SO_4 \to$ green solution.
$[X]$ and $[Y]$ are:

Which ion's salt solution produces a violet layer when chlorine water and chloroform are added?

Molar mass of the salt from $NaBr$,$NaNO_3$,$KI$,and $CaF_2$ which does not evolve coloured vapours on heating with concentrated $H_2SO_4$ is . . . . . . $g \ mol^{-1}$. (Molar mass in $g \ mol^{-1}$: $Na: 23$,$N: 14$,$K: 39$,$O: 16$,$Br: 80$,$I: 127$,$F: 19$,$Ca: 40$)