# The number of litres of air required to burn 8 litres of C2H2 is approximately?

Jun 3, 2017

We need a stoichiometric equation, ...................and get an approx. volume of $100 \cdot L$ air.........

#### Explanation:

We need a stoichiometric equation to represent the combustion:

$H C \equiv C H \left(g\right) + \frac{5}{2} {O}_{2} \left(g\right) \rightarrow 2 C {O}_{2} \left(g\right) + {H}_{2} O \left(l\right)$

And thus given that at constant pressure, and constant temperature (conditions that must be reasonably assumed!), one volume of acetylene gas requires $\frac{5}{2}$ volumes of dioxygen for complete combustion..........

And so, if there are $8 \cdot L$ of acetylene, we requires a volume of 8*Lxx5/2=??L dioxygen gas.........

But we are not finished there (says he, finally reading the question!). The percentage of oxygen in air BY volume, is approx. 21%.

And thus we need a volume of ....

(20*L*O_2)/(0.21*L*O_2*L^-1*"air")~=100*L*"air".........