有CH4及C2H2的混合氣體50毫升，通入過量氧氣後，使之完全燃燒。在同溫同壓下，測得產物CO2的氣體80毫升，求原來CH4與C2H2的莫耳數比為多少? 求算式?

設混合物中有 x 毫升 CH₄ 及 y 毫升 C₂H₂。

CH₄ + 2O₂ → CO₂ + 2H₂O
燃燒 x 毫升的 CH₄，產生 CO₂ 的體積 = x 毫升

2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O
燃燒 y 毫升的 C₂H₂，產生 CO₂ 的體積 = y * (4/2) 毫升 = 2y 毫升

混合物總體積： x + y = 50 ….[1]
產生 CO₂ 的總體積： x + 2y = 80 ….. [2]

[2] - [1]：
y = 30

將y = 30 代入 [1] 中：
x + 30 = 50
x = 20

莫耳數比 CH₄ : C₂H₂
= 體積比 CH₄ : C₂H₂
= 20 : 30
= 2 : 3

先看CH4,
CH4+2O2->CO2+2H2O
no. of mol of CH4 combusted=no. of mol of CO2 produced
再看C2H2,
C2H2+5/2O2->2CO2+H2O
no. of mol of C2H2 combusted=1/2(no. of mol of CO2 produced)
no. of mol of CO2 produced by C2H2: no. of mol of CO2 produced by CH4=2:1
no. of CO2 produced by C2H2=80(2/3)=53.3
no. of CO2 produced by CH4=80(1/3)=26.7
no. of CH4=26.7
no. of C2H4=50-26.7=23.3
C2H2:CH4=1:1.15