| Hydrogen | Test for hydrogen by using a burning splint held at the open end of a test
tube of gas. Hydrogen burns rapidly with a pop sound, so this test is sometimes
called the "squeaky pop test". | The hydrogen causes an explosion.
2H2(g) + O2(g) -> 2H2O(l) |
| Oxygen | Oxygen can be tested for using a glowing splint inserted into a test type of the gas.
The splint will re-light in oxygen. | The splint uses the oxygen for the combustion reaction, so it is re-ignited. |
| Carbon dioxide | The test for carbon dioxide uses an aqueous solution of calcium hydroxide (also known
as limewater). When carbon dxoide is bubbled through limewater, the limewater turns
milky/cloudy (technically, this is a "white precipitate"). | Carbon dioxide reacts with calcium dioxide to form calcium carbonate.
CO2(g) + Ca(OH)2(aq) -> CaCO3(s) + H2O(l) |
| Chlorine | The test for chlorine gas uses litmus paper. When damp litmus paper is put into
chlorine gas, the litmus paper is bleached and turns white. | When chlorine gas comes into contact with moist (damp) litmus paper,
it first dissolves slightly in the water present on the paper,
forming a mixture that includes hypochlorous acid (HOCl) and hydrochloric acid (HCl). |
