Question

A mixture of salts (Na2SO3 + K2Cr2O7) in a test tube is treated with dil. H2SO4 and resulting gas is passed through lime water. Which of the following observations is correct about this test?

(a) Solution in test tube becomes green and lime water turns milky.

(b) Solution in test tube is colourless and lime water turns milky.

(c) Solution in test tube becomes green and lime water *** clear.

(d) Solution in test tube *** clear and lime water also remain clear.

Answer 1

Correct option (c)

Explanation:

Na2SO3 with dil. H2SO4 gives SO2 gas which reacts with K2Cr2O7 to give a green solution due to Cr2( SO4)3. Since whole of the gas is consumed, the lime water will remain clear.

Na2SO3 + H2SO4 → Na2SO4 + SO2 + H2O

K2Cr2O7 + 3SO2 + H2SO4→ K2SO4 + (green) Cr2( SO4)3 + H2O