Before the brown ring test for nitrate, Br^- and I^- must be removed because

conc. H2SO4 oxidises them to Br2 and I2, whose brown or violet colour masks the ring

they reduce Fe^2+ to iron metal

they form insoluble bromide and iodide with FeSO4 which sinks to the bottom

JEE Main levelSingle correct optionDifficulty 2 of 3qa208

Before the brown ring test for nitrate, $Br X^{-}$ and $I X^{-}$ must be removed because

Aconc. $H X_{2} SO X_{4}$ oxidises them to $Br X_{2}$ and $I X_{2}$ , whose brown or violet colour masks the ring
Bthey reduce $Fe X^{2 +}$ to iron metal
Cthey convert $NO$ to $N X_{2}$
Dthey form insoluble bromide and iodide with $FeSO X_{4}$ which sinks to the bottom

The test uses conc.

H X_{2} SO X_{4}

and

FeSO X_{4}

. Bromide and iodide are oxidised to

Br X_{2}

(brown) and

I X_{2}

(violet or brown), which obscure the brown ring at the interface. They do not reduce

Fe X^{2 +}

or form insoluble iron salts.