Balanced Symbol Equation
Contents
Key Stage 3
Meaning
A Balanced Symbol Equation is a way to show the reactants and products in a chemical reaction using the chemical formulae of the reactants and products.
About Balanced Symbol Equations
- Balanced Symbol Equations shows the number of molecules of each chemical and the numbers of each atom within those chemicals.
- Balanced Symbol Equations can be used to find the quantity of each chemical needed to have a complete chemical reaction.
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| This shows there are two H2 molecules and one O2 molecule needed to make two molecules of H2O. |
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| This shows there is one CH4 molecule and two O2 molecules needed to make one molecule of CO2 and two molecules of H2O. |
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| This shows there are two atoms of Mg and one molecule of O2 needed to make two molecules of MgO. |
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| This shows there are two HCl molecules and one Li2O molecule needed to make two molecules of LiCl and one molecule of H2O. |
Balancing Equations
- You may know the chemical formulae of the reactants and products but not know the number of each chemical needed. For that you must balance the equation.
- To balance and equation you need the same number of each type of atom on the left as you do on the right.
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There are now too many Lithium atoms in the products so we need 2 in the reactants. |
This equation is balanced: 2Li + F2 → 2LiF |
Lithium + Fluorine → Lithium Fluoride
- _Li + _F2 → _LiF
- Reactants = Products
- 1Li = 1Li
- 2F ≠ 1F
We need 2 Fluorine atoms in the products.
- _Li + _F2 → 2LiF
- Reactants = Products
- 1Li ≠ 2Li
- 2F = 2F
There are now too many Lithium atoms in the products so we need 2 in the reactants.
- 2Li + _F2 → 2LiF
- Reactants = Products
- 2Li = 2Li
- 2F = 2F
This equation is balanced: 2Li + F2 → 2LiF
Aluminium + Chlorine → Aluminium Chloride
- _Al + _Cl2 → _AlCl3
- Reactants = Products
- 1Al = 1Al
- 2Cl ≠ 3Cl
We need the same number of Chlorine atoms on both sides. To do that we can find the Lowest Common Multiple. In this case it is 6, so we times the left 2 Chlorines by 3 and the right 3 Chlorines by 2.
- _Al + 3Cl2 → 2AlCl3
- Reactants = Products
- 1Al ≠ 2Al
- 6Cl = 6Cl
There are now too many Aluminium atoms on the right, so we need to multiply the left Aluminium by 2.
- 2Al + 3Cl2 → 2AlCl3
- Reactants = Products
- 2Al = 2Al
- 6Cl = 6Cl
This equation is now balanced: 2Al + 3Cl2 → 2AlCl3
Aluminium + Oxygen → Aluminium Oxide
- _Al + _O2 → _Al2O3
- Reactants = Products
- 1Al ≠ 2Al
- 2O ≠ 3O
We need the same number of Oxygen atoms on both sides. To do that we can find the Lowest Common Multiple. In this case it is 6, so we times the left 2 Oxygens by 3 and the right 3 Oxygens by 2.
- _Al + 3O2 → 2Al2O3
- Reactants = Products
- 1Al ≠ 4Al
- 6O = 6O
The Oxygen atoms are now balanced but the Aluminium atoms are not. We need 4 times as many Aluminium atoms on the left.
- 4Al + 3O2 → 2Al2O3
- Reactants = Products
- 4Al = 4Al
- 6O = 6O
This equation is now balanced: 4Al + 3O2 → 2Al2O3