Balanced Symbol Equation

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.

The Word Equation has been given above each Balanced Symbol Equation.

This shows there are two H2 molecules and one O2 molecule needed to make two molecules of H2O.

This shows there is one CH4 molecule and two O2 molecules needed to make one molecule of CO2 and two molecules of H2O.

This shows there are two atoms of Mg and one molecule of O2 needed to make two molecules of MgO.

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.

Lithium + Fluorine → Lithium Fluoride

Step 1	Step 2	Step 3
_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

Key Stage 4

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 show 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.

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.

Magnesium Fluoride + Potassium → Potassium Fluoride + Magnesium

Step 1	Step 2	Step 3
_MgF2 + _K → _KF + _Mg Reactants = Products 1Mg = 1Mg 2F ≠ 1F 1K = 1K We need 2 Fluorine atoms in the products.	_MgF2 + _K → 2KF + _Mg Reactants = Products 1Mg = 1Mg 2F = 2F 1K ≠ 2K There are now too many Potassium atoms in the products so we need 2 in the reactants.	_MgF2 + 2K → 2KF + _Mg Reactants = Products 1Mg = 1Mg 2F = 2F 2K = 2K This equation is balanced: MgF2 + 2K → 2KF + Mg