A solution contains both NaNO2 and NaNO3. Which procedure correctly establishes the presence of nitrate?

Boil with excess NH4Cl until nitrite is destroyed as N2, then do the FeSO4 and conc. H2SO4 brown ring test

Add FeSO4 and dilute acetic acid at room temperature and look for a brown colour

Add FeSO4 and run conc. H2SO4 down the side without any pre-treatment

Add dilute H2SO4 and test the gas with lime water

Boil with excess NH4Cl until nitrite is destroyed as N2, then do the FeSO4 and conc. H2SO4 brown ring test

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JEE Advanced levelSingle correct optionDifficulty 3 of 3qa215

A solution contains both $NaNO X_{2}$ and $NaNO X_{3}$ . Which procedure correctly establishes the presence of nitrate?

AAdd $FeSO X_{4}$ and dilute acetic acid at room temperature and look for a brown colour
BAdd $FeSO X_{4}$ and run conc. $H X_{2} SO X_{4}$ down the side without any pre-treatment
CAdd dilute $H X_{2} SO X_{4}$ and test the gas with lime water
DBoil with excess $NH X_{4} Cl$ until nitrite is destroyed as $N X_{2}$ , then do the $FeSO X_{4}$ and conc. $H X_{2} SO X_{4}$ brown ring test

Answer: D

Nitrite also gives the brown colour with

FeSO X_{4}

, so it must be removed first:

NO X_{2} X^{-} + NH X_{4} X^{+} N X_{2} + 2 H X_{2} O

. After its removal the brown ring with conc.

H X_{2} SO X_{4}

is due to nitrate alone. Dilute acetic acid detects only nitrite, direct testing gives a false positive for nitrate, and lime water does not respond to nitrogen oxides.

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A solution contains both NaNOX2​ and NaNOX3​. Which procedure correctly establishes the presence of nitrate?

Answer: D

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A solution contains both $NaNO X_{2}$ and $NaNO X_{3}$ . Which procedure correctly establishes the presence of nitrate?