suppose you have an unknown gas, and wish to determine whether it may be ammonia, hydrogen or carbon dioxide. Describe tests you might use to prove the existence of each of these gases.
Ammonia, odor.
CO2, bubble through Ca(OH)2 water.
H2, see if it pours UP or DOWN (that may sound stupid but it isn't. A vial of hydrogen cannot be poured DOWN to fill another test tube; it can be poured UP to fill another test tube. Also see if it will explode (a small amount of it, please). A test tube of hydrogen gas will give a small "pop" when a burning match is placed near the top of the test tube.