Balancing Equations for practice and visualization - click here

Equations must be balanced to show conservation of mass.  All the atoms (or ions) must be accounted for at the beginning (in the reactants) and at the end (in the products).

 

Notice that there are FOUR HYDROGEN ATOMS  in the reactants and FOUR HYDROGEN ATOMS in the products.  Notice that there are TWO OXYGEN ATOMS in the reactants and TWO OXYGEN ATOMS in the products.

A large 2 will be written in front of the H2 molecule formula to show that we must start with two hydrogen molecules.  A large 2 will be written in front of the H2O molecule formula to show that we must end with two water molecules molecules. No number in front of the O2 means that there is only one oxygen molecule required.

2 H2   +   O2   →  2 H2This equation is balanced - there are the same number of each atom on both sides.
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