Question

$CH_{ 4 } + 2O_{ 2 } \rightarrow CO_{ 2 } + H_{ 2 }O$ is:
A. Combustion reaction
B. Redox reaction
C. Both A and B
D. None of the above

Answer 1

You just need to recall the definitions of combustion and redox reactions. Combustion is the process of burning something and redox reaction is a type of chemical reaction that involves a transfer of electrons between two species. You will finally get the correct answer to this question.

Complete step by step answer:
Let’s discuss the redox and combustion reactions first and simultaneously we will also figure out the answer.
Redox reactions - Redox reactions are oxidation-reduction chemical reactions in which the reactants undergo a change in their oxidation states. The term ‘redox’ is a short form of reduction-oxidation.
The oxidation and reduction reactions always occur simultaneously, such class of chemical reactions was named as the redox reaction or Oxidation-Reduction Reaction.
$CH_{ 4 } + 2O_{ 2 } \rightarrow CO_{ 2 } + 2H_{ 2 }O$
It is a redox reaction because the oxidation number of oxygen in the $O_{ 2 }$ molecule is 0. But in water, its oxidation number is −2, so it is a reduction. In methane, the oxidation number of H = −1 and in $H_{ 2 }O$ its oxidation number of H is +1, so it is oxidation.
Combustion reaction - A combustion reaction is a reaction in which a substance reacts with oxygen gas, releasing energy in the form of light and heat. Combustion reactions must involve $O_{ 2 }$ as one reactant.
$CH_{ 4 } + 2O_{ 2 } \rightarrow CO_{ 2 } + 2H_{ 2 }O$
Hence, this is also a combustion reaction.

Therefore, we can conclude that the correct answer to this question is option C.

Note: You should also know that the substance getting reduced in a chemical reaction is known as the oxidizing agent (here it is oxygen molecule), while a substance that is getting oxidized is known as the reducing agent (here it is methane molecule).