A colourless gas evolved on warming a sodium salt with dilute H2SO4 turns acidified dichromate paper green, and a pale yellow turbidity also develops in the solution. The anion is

JEE Main levelSingle correct optionDifficulty 2 of 3qa026

A colourless gas evolved on warming a sodium salt with dilute $H X_{2} SO X_{4}$ turns acidified dichromate paper green, and a pale yellow turbidity also develops in the solution. The anion is

S X_{2} O X_{3} X^{2 -} + 2 H X^{+} S + SO X_{2} + H X_{2} O

SO X_{2}

turns dichromate green and sulphur gives the turbidity. Sulphite gives

SO X_{2}

with no sulphur, sulphide gives

H X_{2} S

, and nitrite gives brown fumes.