Question

What is the volume of air required to completely burn 1L of CO? Assume that all volumes are measured at same temperature and pressure and also at 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

Hint: We know that one equivalent of carbon monoxide reacts with half equivalents of oxygen molecule to give one equivalent of carbon dioxide gas. As per these stoichiometries, volume can be calculated by recalling that volume is directly proportional to number of moles.
Complete step-by-step answer:
Combustion is a type of chemical reaction in which a fuel or combustible substance burns with oxygen to produce carbon dioxide gas and water. Complete combustion of carbon monoxide means carbon monoxide burns in air and releases carbon dioxide in certain stoichiometric ratios.
 \[2CO + {O_2} \to 2C{O_2}\]
From this chemical equation, we can see that 1mole of carbon monoxide reacts with half moles of oxygen to produce 1 mole of carbon dioxide.
Assuming that change in volume is at the same pressure and temperature, the only thing on which volume now depends on is stoichiometric coefficients. Air contains one-fifth by volume of oxygen i.e. \[20\% \] as the majority of air has nitrogen (\[80\% \]).
We can say that 1 mol of CO needs 0.5 mol of oxygen. In a similar way we can see that 1 litre of CO requires 0.5 litres of oxygen.
Volume of air required = \[\dfrac{{100}}{{20}}\]\[ \times \] oxygen required
= \[\dfrac{{100}}{{20}}\]\[ \times \] \[0.5{\text{ }} = {\text{ }}2.5\] litre air
The volume of air required to completely burn 1L of CO is 2.5 litre air.

Hence, the correct option is (B).

Note: Stoichiometric coefficient is the number that appears before the symbol for each compound in the equation for a chemical reaction. It is determined when the reaction is balanced and explains the quantitative amount of species reacting and forming.