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 $(X)$?

In the test of sulphate radical,the white precipitate of sulphate is soluble in

The phosphate radical reacts with ammonium molybdate to form a precipitate of which color?

$AgNO_3$ gives a red precipitate with:

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 $g \ mol^{-1}$: $Na: 23$,$N: 14$,$K: 39$,$O: 16$,$Br: 80$,$I: 127$,$F: 19$,$Ca: 40$)

The gas evolved when sodium sulfide is heated with dilute $HCl$ is: