A gas X is colourless with a pungent smell, turns acidified K2Cr2O7 green and is emitted on burning sulphur containing coal. Which statements about X are correct?

X acts as a reducing agent in this test.

Sulphur is in the +4 oxidation state in X.

In air, particulates catalyse oxidation of X to SO3.

X acts as a reducing agent in this test.

Sulphur is in the +4 oxidation state in X.

In air, particulates catalyse oxidation of X to SO3.

JEE Advanced levelOne or more correct optionsDifficulty 3 of 3ev050

A gas X is colourless with a pungent smell, turns acidified $K X_{2} Cr X_{2} O X_{7}$ green and is emitted on burning sulphur containing coal. Which statements about X are correct?

X is

SO X_{2}

with S at +4. It reduces Cr(VI) to green Cr(III), is oxidised to

SO X_{3}

in air (particulates catalyse this) and is an acidic oxide, giving

H X_{2} SO X_{3}

with water. It is not a neutral oxide.