How to balance reactions

• To summarize:
• A balanced chemical equation has the same number of atoms of each element in the reactants and products.
• Multiplicative coefficients can be added to balance the equation without changing the identity of the substances involved.

Balancing Redox Reactions

Balancing redox reactions requires a different method than non-redox reactions. In this case, it is necessary to take into account the loss and gain of electrons by the elements involved in the reaction.

Step 1: Write the Half-Reaction

The first thing to do is write the half-reactions for oxidation and reduction. The oxidation half-reaction represents the loss of electrons, while the reduction half-reaction represents the gain of electrons.

• Oxidation half-reaction: Fe → Fe³⁺ + 3e-
• Reduction half-reaction: Cr³⁺ + 3e- → Cr

Step 2: Balance Atoms

Balance the atoms present in the half-reactions, adding stoichiometric coefficients where necessary.

• Oxidation half-reaction: 2Fe → 2Fe³⁺ + 6e-
• Reduction half-reaction: 3Cr³⁺ + 3e- → 3Cr

Step 3: Balance Electrons

Balance the number of electrons between the half-reactions, ensuring that the number of electrons lost in the oxidation half-reaction corresponds to the number of electrons gained in the reduction half-reaction. Multiply the half-reactions by a common factor to get the same number of electrons.

• Oxidation half-reaction: 2Fe → 2Fe³⁺ + 6e-
• Reduction half-reaction: 3Cr³⁺ + 3e- → 3Cr


• Multiply the oxidation half-reaction by 3: 6Fe → 6Fe³⁺ + 18e-
• Multiply the reduction half-reaction by 2: 6Cr³⁺ + 6e- → 6Cr

Step 4: Combine Half-Reactions

Combine the two half-reactions to eliminate electrons present on both sides of the equation. Add like terms on both sides of the equation.

• Oxidation half-reaction: 6Fe → 6Fe³⁺ + 18e-
• Reduction half-reaction: 6Cr³⁺ + 6e- → 6Cr


• Multiply the oxidation half-reaction by 2: 12Fe → 12Fe³⁺ + 36e-
• Multiply the reduction half-reaction by 3: 18Cr³⁺ + 18e- → 18Cr


• Add the two equations: 12Fe + 18Cr³⁺ → 12Fe³⁺ + 18Cr

Practical Examples of Chemical Reaction Balancing

To better understand how to balance chemical reactions, let's look at some practical examples:

Example 1: Balancing the equation for methane combustion

The chemical equation for the complete combustion of methane (CH₄) is:

CH₄ + 2O₂ → CO₂ + 2H₂O

Let's start by counting the atoms on each side of the equation:

• Left side: 1 C, 4 H, 2 O
• Right side: 1 C, 4 H, 4 O

We see that the number of oxygen atoms is not equal on both sides of the equation. To balance it, we need to add a coefficient in front of the O₂, so that we have the same number of oxygen atoms on both sides:

CH₄ + 2O₂ → CO₂ + 2H₂O (Balanced)

• Left side: 1 C, 4 H, 4 O
• Right side: 1 C, 4 H, 4 O

Now the equation is balanced and follows the law of conservation of mass.

Example 2: Balancing the equation for the reaction between hydrochloric acid and sodium hydroxide

The chemical equation for the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH) is:

HCl + NaOH → NaCl + H₂O

Let's start by counting the atoms on each side of the equation:

• Left side: 1 H, 1 Cl, 1 Na, 1 O
• Right side: 1 Na, 1 Cl, 2 H, 1 O

We see that the number of hydrogen and oxygen atoms is not equal on both sides of the equation. To balance it, we need to add coefficients in front of the molecules:

HCl + NaOH → NaCl + H₂O (Balanced)

• Left side: 1 H, 1 Cl, 1 Na, 1 O
• Right side: 1 Na, 1 Cl, 2 H, 1 O

Now the equation is balanced and follows the law of conservation of mass.

These are just two examples of how to balance chemical reactions. In general, the process requires a good understanding of the composition of molecules and the laws governing their interaction. With a little practice, however, it is possible to become skilled at balancing any type of chemical equation.

Conclusions and importance of balancing reactions in chemistry

In conclusion, balancing chemical reactions is a fundamental operation for understanding how chemistry works. Without it, it would not be possible to understand how chemical transformations occur and how desired products can be obtained.

Balancing reactions is also important because it allows us to calculate the exact quantities of reactants needed to obtain a certain amount of product. This is particularly useful in industry, where the production of large quantities of substances requires precise knowledge of the proportions of the reactants.

In addition, balancing reactions is the basis of stoichiometry, which is the study of quantitative relationships between substances that participate in a reaction. Stoichiometry is essential for understanding how to vary the conditions of a reaction in order to achieve maximum yield or maximum purity of the product.

A practical example of the importance of balancing reactions can be given by the synthesis of water through the combustion of hydrogen. If the reaction is not balanced correctly, different amounts of water and oxygen could be formed than those predicted by the formula H ₂+O₂=H₂O. This could lead to safety and efficiency issues in water production.

In conclusion, balancing chemical reactions is a fundamental operation for understanding chemistry and for the practical application of this science. Without it, we would be unable to understand how chemical transformations occur and how desired products can be obtained.

Conclusion of the article

Balancing reactions in chemistry is a fundamental skill for all students studying this subject. Knowing the rules for balancing a reaction allows for a better understanding of how chemistry works and how it can be effectively applied in different contexts, from scientific research to industry. Additionally, balancing reactions is the basis of stoichiometry, which is the study of quantitative relationships between substances involved in a reaction. Stoichiometry is essential for accurately calculating the quantities of reactants needed to obtain a certain product and for varying reaction conditions to maximize yield or purity of the final product.