Question

Air contains $20$ percent oxygen by volume. Calculate the theoretical volume of air which will be required for burning $200m^3$ of acetylene gas completely. All volumes are measured under the same conditions of temperature and pressure.

• A. $2500m^3$
• B. $500m^3$
• C. $5000m^3$
• D. $3000m^3$

Answer 1

The correct option is A $2500m^3$

Under STP conditions,
$200m^3$ of acetylene corresponds to $200\times 1000\times \frac{1}{22.4}=8928.5$ moles.
The combustion reaction is $2C_2{H}_2+5O_2\rightleftharpoons 4C{O}_2+2H_{2}O$.
Thus, $2$ moles of acetylene require $5$ moles of oxygen.
Hence, the number of moles of oxygen required $=8928.5\times \frac{5}{2}=22321moles$, i.e. 500 $m^3$.
The volume of air required is $500m^3\times \frac{100}{20}=2500m^3$.