Lab Tests for Gases

Test for oxygen :

Gas collected is able to relight a glowing splint (light a wooden splint, blow it out and then insert it quickly into the gas chamber)

Test for carbon dioxide :

1. Bubbling carbon dioxide through lime water (calcium hydroxide) makes it cloudy due to solid precipitates of calcium carbonate.
   Ca(OH)₂ (aq) + CO₂ (g) --> CaCO₃ (s) + H₂O (aq)>
2. Putting a lit splint into the gas collection chamber will put out the fire, as CO2 does not support combustion.
3. Dissolved carbon dioxide lowers the pH of a solution. Carbon dioxide reacts with water to form carbonic acid.
   CO₂ (g) + H₂O (aq) <==> H₂CO₃ (aq)
   

Test for nitrogen :

Nitrogen is extremely neutral and there does not change the color of moist litmus or indicator paper, neither does it have color or smell. It is also non-combustible and will put out a lit splint.

Test for hydrogen:

Burns with a 'pop' sound - which is actually a small explosion as hydrogen is extremely flammable!

Test for chlorine gas :

1. It is green-yellow in color, and smells pungent.
2. It turns moist litmus/universal indicator paper red, then white.
3. Since it is not combustible, it puts out a lit splint just like carbon dioxide.

To absorb carbon dioxide :

Place a strong alkaline/base in solid form (pellets, flakes) such as sodium hydroxide (NaOH), potassium hydroxide (KOH) or lithium hydroxide (LiOH) to absorb carbon dioxide.