Question

A gas mixture of 3 litres of propane $\left(C_3{H}_8\right)$ and butane $\left(C_4{H}_{10}\right)$ on complete combustion at ${25}^o$ produced 10 litre $C{O}_2.$ Find out the composition of gas mixture (Propane : Butane)

• A. $3:1$
• B. $1:2$
• C. $2:1$
  
• D. $1:1$

Answer 1

The correct option is C $2:1$


Balanced equation for combustion reactions:
$\underset{a}{C_3{H}_8}+5O_2\to \underset{3a}{3C{O}_2}+4H_{2}O$
$\underset{(3-a)}{C_4{H}_{10}}+\frac{13}{2}{O}_2\to \underset{4(3-a)}{4C{O}_2}+5H_{2}O$
Applying Gay Lussac's law,
$3a+4(3-a)=10$
$\Rightarrow a=2$
$\therefore$ a = 2(Propane) and 3 - 2 = 1 (Butane)
Hence, 2 : 1
(Propane : butane)