Question

Which chemical equation shows the incomplete combustion of methane?

A. C3H8 + 5O2 → 3CO2 + 4H2O
B. 2CH4 + 3O2 → 2CO + 4H2O
C. CH4 + 2O2 → CO2 + 2H2O

Answer 1

Combustion is a chemical reaction in which a hydrocarbon reacts with oxygen to form carbon dioxide (CO2) and water (H2O). In other words, all the carbons get converted to CO2 while all the hydrogens get converted into H2O.

Incomplete combustion however, results in the formation of carbon monoxide (CO) and H2O.

Methane is a hydrocarbon with a molecular formula CH4. Thus complete combustion of methane can be expressed as-

CH4 + 2O2 → CO2 + 2H2O

Ans (C)

Answer 2

Answer : The incomplete combustion equation of methane is, (B)
`2CH_4+3O_2\rightarrow 2CO+4H_2O`

Explanation :

Combustion reaction : It is defined as the reaction in which a hydrocarbon react with oxygen to give carbon dioxide and water as a product.

As per question, the combustion of methane (a hydrocarbon) also gives carbon dioxide and water as a product.

The balanced combustion reaction of methane will be,

`CH_4+2O_2\rightarrow CO_2+2H_2O`

By the stoichiometry we can say that, 1 mole of methane react with 2 moles of oxygen to give 1 mole of carbon dioxide and 2 moles of water.

So, option (B) is an incomplete combustion reaction of methane and option (A) is the balanced combustion reaction of pentane.

Hence, the incomplete combustion equation of methane is, (B)
`2CH_4+3O_2\rightarrow 2CO+4H_2O`