2.39      describe simple tests for the gases:

Gas	Test	Results
i    hydrogen (H2)	introduce lighted splint	explodes with squeaky pop
ii   oxygen (O2)	introduce glowing splint	reignites the splint
iii  carbon dioxide (CO2)	bubble through lime water	goes milky white*
iv   ammonia (NH3)	introduce moist red litmus paper	turns blue
v    chlorine (Cl2)	introduce moist indicator paper (any colour)	indicator paper is bleached white

Note:    The limewater goes milky because a white precipitate of insoluble calcium carbonate is formed. The equation for limewater (calcium hydroxide) reacting with carbon dioxide is:

Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)