Question

Which coefficients balance this equation? `?CH_4 + ?O_2 -> ?CO_2 + ?H_2O`

Answer 1

`"CH"_4+color(red)2"O"_2"` `rarr` `"CO"_2+color(blue)2"H"_2"O"`

Explanation:

A chemical equation represents a chemical reaction in which chemical bonds in the reactants break and form new bonds in the products. Because of the law of conservation of matter, there needs to be the same number of atoms of each element on both sides. We balance chemical equations by adding coefficients in front of the formulas as needed. NEVER change the subscript in any formula.

The chemical equation is an example of the combustion of a hydrocarbon methane, `"CH"_4"`.

`"CH"_4+"O"_2"` `rarr` `"CO"_2+"H"_2"O"`

First balance the carbon atoms.

`"CH"_4+"O"_2"` `rarr` `"CO"_2+"H"_2"O"`

The carbon atoms are balanced already with one on each side.

Next balance the hydrogen atoms.

`"CH"_4+"O"_2"` `rarr` `"CO"_2+"H"_2"O"`

There are four hydrogen atoms on the left-hand side and two on the right-hand side.

Add a coefficient of `2` in front of the `"H"_2"O"`.

`"CH"_4+"O"_2"` `rarr` `"CO"_2+color(blue)2"H"_2"O"`

Now balance the oxygen atoms.

There are two oxygen atoms on the left side and four on the right.

Add a coefficient of `2` in front of `"O"_2"` on the left side.

`"CH"_4+color(red)2"O"_2"` `rarr` `"CO"_2+color(blue)2"H"_2"O"`

We now have 1 C atom on both sides, 4 hydrogen atoms on both sides, and 4 oxygen atoms on both sides and the equation is balanced.

In words we would say "One molecule (or mole) of methane plus two molecules (or moles) of oxygen gas produce one molecule (or mole) of carbon dioxide plus two molecules (or moles) of water.

Reference: http://yeahchemistry.com/tutorials/balancing-combustion-reactions