Question

If butane on combustion gives carbon monoxide, find the number of ${O_2}$ molecules required?
A.6
B.5.5
C.4.5
D.4

Answer 1

Hint: Butane is undergoing incomplete combustion. In complete combustion means there is not enough oxygen (insufficient percentage) present in the air for all of the carbon atoms in butane to turn into carbon dioxide. Some or all of it turns into carbon monoxide or carbon particles.

Complete step by step answer:
The chemical equation needs to be balanced so that it follows the law of conservation of mass. This law states that the mass of any one element at the beginning of a reaction should be equal to the mass of that element at the end of the reaction.
Each mole of butane needs 6.5 moles of oxygen, so 13 moles of oxygen are required for 2 moles of butane in a complete combustion.
The balanced chemical equation for this process is as shown:
${C_4}{H_{10}} + \dfrac{9}{2}{O_2} \to 4CO(g) + 5{H_2}O(l)$
In the above equation,
We can see that the number of ${O_2}$ molecules required for complete combustion,
$ = \dfrac{9}{2}$
$ = 4.5mol$
Therefore, the number of ${O_2}$ molecules required are 4.5 mol

Hence, option C is correct.

Note:
Butane is a gas at room temperatures and normal atmospheric pressure. When there is oxygen present, butane can burn to form carbon dioxide and water vapor. However, if there isn’t enough oxygen available, burning butane can produce toxic and dangerous carbon monoxide as its waste product.