EDTECH Worked Example

What do both sides of a chemical equation have to have to make a balanced equation?

The same number of (a)   of each element on both sides of the yield arrow.

Answer explanation

Because the Law of Conservation of Matter states that matter cannot be created or destroyed in a chemical reaction, there must be the same number of atoms of each element in reatants and the products.

Balance the chemical equation:

Al₂O₃ --> Al + O₂

• Al₂O₃ --> Al + O₂

• 2Al₂O₃ --> 2Al +2 O₂

• 2Al₂O₃ --> 4Al + 3O₂

• 2Al₂O₃ --> 2Al + 5O₂

Answer explanation

2Al₂O₃ --> 4Al + 3O₂ is correct.

On our reactants side, we have:

(2 * 2) = 4 Al atoms

(2* 3) = 6 O atoms

On our product side, we have:

(4 * 1) = 4 Al atoms

(3*2) = 6 O atoms

Balance the chemcial equation:

Fe + Cl₂ ---> FeCl₃

• 2Fe + 3Cl₂ ---> 2FeCl₃

• Fe + Cl₂ ---> FeCl₃

• Fe + 2Cl₂ ---> 2FeCl₃

• 4Fe + 7Cl₂ ---> 4FeCl₃

Answer explanation

2Fe + 3Cl₂ ---> 2FeCl₃

On our reactants side, we have:

(2 * 1) = 2 Fe atoms

(3 * 2) = 6 Cl atoms

On our product side, we have:

(2 * 1) = 2 Fe atoms

(2 * 3) = 6 Cl atoms

Balance the chemical equation:

N₂ + H₂ ---> NH₃

• 3N₂ + 3H₂ ---> 2NH₃

• N₂ + H₂ ---> NH₃

• 2N₂ + 3H₂ ---> 4NH₃

• N₂ + 3H₂ ---> 2NH₃

Answer explanation

N₂ + 3H₂ ---> 2NH₃

On our reactants side, we have:

(1 * 2) = 4 N atoms

(3 * 2) = 6 H atoms

On our product side, we have:

(2 * 1) = 2 N atoms

(2 * 3) = 6 H atoms

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