Question

Give the characteristic tests for the following gases:
i. CO₂ 

ii. SO₂
iii. O₂

iv. H₂

Answer 1

Characteristic tests:
i. CO₂: Pass the CO₂ gas through lime water. It will turn lime water milky. This occurs due to formation of calcium carbonate.

ii. SO2: Pass the SO2 gas through acidified potassium dichromate solution (orange in colour). The solution changes to green in colour due to formation of Cr₂(SO₄)₃. In this reaction, SO₂ act as reducing agent.

iii. O₂: Bring a burning candle near the mouth of the test tube containing reaction mixture. If oxygen gas is present, then the intensity of the candle flame increases as oxygen supports combustion.

iv. H2: Bring a burning splinter near the mouth of the test tube containing reaction mixture. Hydrogen gas, if present, will burn with pop sound.