question_answer 68)

  Give the characteristic tests for the following gases. (a) CO2                                  (b) SO2                                                   (c) O2                                     (d) H2

Answer:

  (a) Test for CO2 gas (lime water test) When CO2 gas is passed through lime water, it turns milky due to the formation of insoluble calcium carbonate. If the gas is in excess, milkiness disappears due to the formation of soluble calciumbi carbonate. (b) Test for SO2gas (i) Sulphur dioxide gas turns moist litmus paper from blue to red because SO, is acidic in (ii) Sulphur dioxide gas turns acidified potassium dichromate (vi) solution from orange to green. (c) Test for O2 gas When a wooden splinter is brought near the mouth of the gas jar containing oxygen gas, it burns brightly as oxygen is the supporter of combustion. (d) Test for K, gas Hydrogen gas burns in the presence of air or oxygen with a pop sound when a burning candle is brought near it.