Question

How would you write a balanced chemical equation for $C{H_4}$ reacting with oxygen gas to produce water and carbon dioxide?

Answer 1

A balanced chemical equation is an equation which has the same number of individual atoms on either side of the equation. The total mass of the reactants of a balanced equation is equal to the total mass of the products.

Complete step by step answer:
A chemical equation is a symbolic representation of the elements of the compound taking part in a reaction. The substances which are present on the left hand side of the equation are called reactants or substrates. The substances on the right hand side of the equation are called the products of the reaction.
Now a chemical equation is said to be balanced when the number of atoms of the molecules involved in both sides of the equation are equal. This is also related to the mass of the molecules as the total mass of the reactants must be equal to the total mass of the products. This equilibration of mass is also referred to as the law of conservation of mass.
The reactants of the given reaction are methane and oxygen. The products of the given reaction are carbon dioxide and water. Thus the reaction is written as
$C{H_4} + {O_2} \to C{O_2} + {H_2}O$
Looking at the equation reveals that the number of carbon is the same on both sides of the equation. But the number of oxygen and hydrogen are not the same. Thus multiplying the number of moles of oxygen and water by a factor $2$, gives the required balanced chemical equation. The equation is written as
$C{H_4} + 2{O_2} \to C{O_2} + 2{H_2}O$
The above equation is the balanced chemical equation for $C{H_4}$ reacting with oxygen gas to produce water and carbon dioxide.
The balanced equation satisfies the law of conservation of mass. One molecule of methane reacts with two molecules of oxygen producing one molecule of carbon dioxide and two molecules of water.

Note:
The law of conservation of mass states that none of the atoms involved in a chemical reaction are created or destroyed. Thus the number of atoms present in the reactants side must balance the number of atoms present in the products side.