Name the products obtained on complete combustion of hydrocarbons? How is the gas evolved during combustion tested in the laboratory? Explain in brief.
Hydrocarbons upon complete combustion give carbon dioxide and water along with heat and/or light. Complete combustion of alkanes are represented by:
CxHy + (x+y/4)O2→ xCO2 + (y/2)H2O
where ‘x’ is the number of carbon atoms and ‘y’ is the number of hydrogen atoms. The gas evolved is carbon dioxide. To test its presence, one can pass the gas through lime water (calcium hydroxide) turning it milky due to the formation of calcium carbonate.
Ca(OH)2 + CO2 → CaCO3 + H2O