Both sodium carbonate and sodium sulphite give a gas that turns lime water milky when treated with dilute H2SO4. Which observation with the evolved gas distinguishes the sulphite from the carbonate?

It decolourises acidified KMnO4 solution

It turns moist blue litmus paper red

It decolourises acidified KMnO4 solution

It is evolved with effervescence on adding dilute acid to the solid

JEE Main levelSingle correct optionDifficulty 2 of 3qa171

Both sodium carbonate and sodium sulphite give a gas that turns lime water milky when treated with dilute $H X_{2} SO X_{4}$ . Which observation with the evolved gas distinguishes the sulphite from the carbonate?

SO X_{2}

is a reductant and reduces purple

MnO X_{4} X^{-}

to colourless

Mn X^{2 +}

while

CO X_{2}

does not. The other three observations (milky lime water, acidic gas reddening blue litmus, effervescence) are shared by

CO X_{2}

and

SO X_{2}

and so cannot distinguish them.