Which of the following observations on warming the sodium salt with concentrated H2SO4 (with copper turnings for nitrate) are correct? One or more options may be correct.

Bromide: reddish-brown vapour of Br2 along with HBr.

Oxalate: a mixture of CO and CO2 is evolved.

Nitrate with Cu turnings: brown fumes of NO2 and a blue solution.

Bromide: reddish-brown vapour of Br2 along with HBr.

Chloride: greenish-yellow Cl2 even without any oxidising agent.

Oxalate: a mixture of CO and CO2 is evolved.

Nitrate with Cu turnings: brown fumes of NO2 and a blue solution.

JEE Advanced levelOne or more correct optionsDifficulty 3 of 3qa091

Which of the following observations on warming the sodium salt with concentrated $H X_{2} SO X_{4}$ (with copper turnings for nitrate) are correct? One or more options may be correct.

Concentrated acid and Cu reduce nitrate to brown

NO X_{2}

with blue

Cu X^{2 +}

HBr

is partly oxidised by concentrated

H X_{2} SO X_{4}

to red-brown

Br X_{2}

. Oxalic acid is dehydrated to

CO + CO X_{2} + H X_{2} O

. Chloride gives only colourless fuming HCl, because

HCl

is not oxidised by concentrated

H X_{2} SO X_{4}

; chlorine needs

MnO X_{2}

. Correct: first, second and fourth.