EDTECH Worked Example

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

The same number of _____ 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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