$A$ mixture is heated with dilute $H_2SO_4$ and the lead acetate paper turns black due to the evolved gases. The mixture contains:

Which of the following reagents would you use to separate $SO_4^{2-}$ ions from a solution containing a mixture of $SO_4^{2-}$ and $Cl^-$ ions?

To an inorganic mixture,dilute $H_2SO_4$ is added in the cold; a colourless,odourless gas is evolved. The mixture contains:

Assertion $(A) :- Fe^{+3}$ is not used in the brown ring test for $NO_3^{-}$.
Reason $(R) :-$ Reduction of $NO_3^{-}$ takes place during the test.

$A$ substance on treatment with dilute $H_2SO_4$ liberates a colourless gas which produces:
$(i)$ turbidity with baryta water and
$(ii)$ turns acidified dichromate solution green.
The reaction indicates the presence of:

Formation of $Na_4[Fe(CN)_5NOS]$,a purple coloured complex formed by addition of sodium nitroprusside in sodium carbonate extract of salt indicates the presence of $:$