👇 Frequently asked in IGCSE Chemistry exams are questions on balancing chemical equations. 👇

When you are balancing chemical equations,

🚨The number of atoms of each element should be the same on each side of the equation 🚨

Example 1

Balance the equation for the reaction between sodium and water.

Step 1. Identify the reactants and products of the reaction, and write the word equation.

Reactants: sodium and water

Products: sodium hydroxide and hydrogen gas

Word equation:

sodium + water → sodium hydroxide + hydrogen

Step 2. Write an unbalanced chemical equation by finding out the molecular formula for each substance.

Na + H₂O → NaOH + H₂ 

Step 3. Balance the chemical equation by making the number of atoms of each element on each side of the equation equal.

᛫ Sodium: There is one sodium atom on the left and one on the right, so it is balanced.

᛫ Hydrogen: There are two hydrogen atoms on the left and three on the right, so H₂ should be (1/2)H₂.

Na + H₂O → NaOH + (1/2)H₂ 

                     To keep the coefficients in the simplest whole number ratio, multiply all the coefficients by 2.

2Na + 2H₂O → 2NaOH + H₂ 

᛫ Oxygen: There are two oxygen atoms on the left and two on the right, so it is balanced.

Step 4. Make sure the equation is balanced by comparing the number of atoms of each element.

Example 2

Sodium sulfate can be made from sodium hydroxide and sulfuric acid. Balance the equation for the reaction between sodium hydroxide and sulfuric acid.

Step 1. Identify the reactants and products of the reaction, and write the word equation.

Reactants: sodium hydroxide and sulfuric acid

Products: sodium sulfate and water

Word equation:

sodium hydroxide + sulfuric acid → sodium sulfate + water

Step 2. Write an unbalanced chemical equation by finding out the molecular formula for each substance.

NaOH + H₂SO₄ → Na₂SO₄ + H₂O

Step 3. Balance the chemical equation by making the number of atoms of each element on each side of the equation equal.

᛫ Sodium: There is one sodium atom on the left and two on the right, so NaOH should be 2NaOH.

2NaOH + H₂SO₄ → Na₂SO₄ + H₂O

᛫ Sulfur: There is one sulfur atom on the left and on the right, so it is balanced.

᛫ Oxygen: There are six oxygen atoms on the left and five on the right, so H₂O should be 2H₂O.

2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

᛫ Hydrogen: There are four hydrogen atoms on the left and on the right, so it is balanced.

Step 4. Make sure the equation is balanced by comparing the number of atoms of each element.

Example 3

Iron(III) oxide can be reduced by carbon. Write a balanced equation for this reaction.

Step 1. Identify the reactants and products of the reaction, and write the word equation.

Reactants: iron(III) oxide and carbon

Products: iron and carbon dioxide

Word equation:

iron(III) oxide + carbon → iron + carbon dioxide

Step 2. Write an unbalanced chemical equation by finding out the molecular formula for each substance.

Fe₂O₃ + C → Fe + CO₂ 

Step 3. Balance the chemical equation by making the number of atoms of each element on each side of the equation equal.

᛫ Iron: There are two irons on the left and one iron on the right, so Fe should be 2Fe.

Fe₂O₃ + C → 2Fe + CO₂ 

᛫ Oxygen: There are three oxygen atoms on the left and two oxygen atoms on the right, so CO₂ should be (3/2)CO₂.

Fe₂O₃ + C → 2Fe + (3/2)CO₂ 

                  To keep the coefficients in the simplest whole number ratio, we multiply all the coefficients by 2.

2Fe₂O₃ + 2C → 4Fe + 3CO₂ 

᛫ Carbon: There are two carbon atoms on the left and three carbon atoms on the right, so 2C should become 3C.

2Fe₂O₃ + 3C → 4Fe + 3CO₂ 

Step 4. Make sure the equation is balanced by comparing the number of atoms of each element.

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