The nitrogen has been reduced or has undergone reduction and it has gained one electron
A should be the products and D should be the reactants. So D should be the answer.
Answer:
The correct answer is : No, because there are 4 hydrogen atoms on the reactants side and 2 on the products side.
Explanation:

The given reaction equation is not balanced because:
- Number of hydrogen atoms on both sides are not equal that is 4 on reactants side and 2 on products side.
- Number of oxygen atoms on both sides are not equal that is 3 on reactants side and 2 on products side.
In a balanced chemical equation number of atoms of each elements are equal on both sides.
So, the balanced chemical equation will be:

Use the equation for density :
Density = mass / volume
Density = 120 / 480
Density = 0.25
Answer: The balanced equation for the complete oxidation reaction that occurs when methane (CH4) burns in air is
.
Explanation:
When a substance tends to gain oxygen atom in a chemical reaction and loses hydrogen atom then it is called oxidation reaction.
For example, chemical equation for oxidation of methane is as follows.

Number of atoms present on reactant side are as follows.
Number of atoms present on product side are as follows.
To balance this equation, multiply
by 2 on reactant side. Also, multiply
by 2 on product side. Hence, the equation can be rewritten as follows.

Now, the number of atoms present on reactant side are as follows.
Number of atoms present on product side are as follows.
Since, the atoms present on both reactant and product side are equal. Therefore, this equation is now balanced.
Thus, we can conclude that balanced equation for the complete oxidation reaction that occurs when methane (CH4) burns in air is
.