How do you demonstrate a chemical equations is balanced?

Answer 1

This is quite simple, you count up the number of ATOMS on each side of the "=>" sign, the rules for this are:-

1. In a chemical formula a "letter or symbol for an atom of an Element" followed by a number (usually expressed as a subscript) denotes how many ATOMS of that element are present in that molecule.
2. A number before a "formula for a compound or molecule" denotes the number of those molecules present.
3. The mathematical symbol "+" shows which groups of molecules are present in the equation.

Thus:-

The balanced equation for the formation of water from its elemental components (gaseous Hydrogen and gaseous Oxygen) is:-

2H2+O2 => 2H2O

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Using the rules 1-3 above we can see that the products (after the "=>") of the reaction, contain 2 ATOMS of Hydrogen and 1 ATOM of Oxygen - H2O, but that there are two water molecules present making 4 ATOMS of Hydrogen and 2 ATOMS of Oxygen - a total of 6 ATOMS.

Now looking at the reactants (before the "=>") we see that hydrogen and Oxygen gases are "diatomic" (this means that the molecule contains 2 a pair of ATOMS) - H2 and O2. Thus if you reacted one Hydrogen molecule with one Oxygen molecule you would use up all the Hydrogen but only one of the Oxygen ATOMS. Thus you would need TWO Hydrogen molecules to use up all the Oxygen - thus the "2" in front of the "H2". So adding up all the reactants' ATOMS, we get 4 Hydrogen ATOMS and 2 Oxygen ATOMS - a total of 6 ATOMS.

Thus we can write

2 molecules of Hydrogen and 1 molecule of Oxygen which contain 6 ATOMS, 4 of Hydrogen and 2 of Oxygen reacted to produce 2 molecules of Water which contain 6 ATOMS, 4 of Hydrogen and 2 of Oxygen.

There are the same number of ATOMS either side of the equation AND the same number of ATOMS for EACH ELEMENTeither side of the equation. This means the equation is balanced. This has to be because matter can neither be created or destroyed in normal circumstances.

Answer 2

By determining whether the numbers of each kind of atoms in the equation are the same on both sides of the equation.

Answer 3

Count the number of atoms of each element on either side, they should be equal in umber if the equations is balanced.