Britannica Sources used in this answer

How is the equation for hydrogen reacting with oxygen to form water balanced?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

combustion — chemical reaction Log burning in a fire. Burning wood is an example of a chemical reaction in which wood in the presence of heat and oxygen is transformed into carbon dioxide, water vapor, and ash.

To balance the chemical equation for the reaction of hydrogen and oxygen to form water, you must ensure that the number of atoms for each element is equal on both sides of the equation, in accordance with the law of conservation of mass.12

The unbalanced equation is:
$H_{2} + O_{2} \to H_{2} O$

To balance it, follow these steps:

Count the atoms: On the left, there are 2 hydrogen (H) atoms and 2 oxygen (O) atoms. On the right, there are 2 H atoms and 1 O atom.1
Adjust coefficients: To equalize the oxygen atoms, place a coefficient of 2 in front of the product $H_{2} O$ . This results in 2 oxygen atoms on the right, but it also increases the hydrogen count to 4.1
Finalize: To balance the 4 hydrogen atoms now on the right, place a coefficient of 2 in front of the $H_{2}$ on the left.1

The final balanced equation is:
$2 H_{2} + O_{2} \to 2 H_{2} O$ 12

This indicates that two molecules of hydrogen react with one molecule of oxygen to produce two molecules of water.2