Question

What is the volume of air required to completely burn $1L$ of $CO?$ Assume that all volumes are measured at the same temperature and pressure and also that air contains one-fifth by volume of $O_2$.

• A. $2$ litre air
• B. $2.5$ litre air
• C. $5$ litre air
• D. $3.5$ litre air

Answer 1

Answer: (B)

$2.5$ litre air

Air contains $V_5$ of $O_2$ by volume:

$\Rightarrow 5l$ of air contains $\frac{1}{5}\times 5=1l$ of $O_2$

For complete combustion:

$2CO+O_2\to {2CO}_2$

Volume ratio $=2:1:2$

$\therefore$ for combustion of $1l$ of $CO=0.5l$ of $O_2$ is required.

$1l$ of $O_2$, is contained in $5l$ of air.

$\therefore$ $0.5l$ of $O_2$ is combined in $5\times 0.5l$ of air $=2.5l$ of air.