The process of determining the constituents of a gaseous mixture by there cheical reactions is called eudometry.
To solve these problems you must know the reactions of gases. Now you carry out some processes that can qive you athe composition of that mixture. The reactions may be combustion of gases. (One mole of methane on reacting with 2 moles of oxyegen give C)2 and two moles of H20) or like CO2 on passing through solution of KOH is absorbed in it.
Now with this knowledge try to solve some problems and if you can'y solve them please ask us again
Krishna Gopal Singh
B.Tech Chemical Engg
IIT Delhi 2002
Currently doing PhD from IIT Delhi