Reactions: Redox Equation | Active Summary

Objectives

1. Identify redox reactions and understand the variation of oxidation numbers (nox) of the substances involved.

2. Clearly differentiate oxidizing and reducing agents in a chemical reaction.

Contextualization

Did you know that redox reactions are everywhere, from the cellular respiration process that occurs in our body to the corrosion of metals that we see daily? These reactions are not only fundamental for understanding how energy is transferred in biological systems, but they are also crucial in technologies such as batteries and cells. By understanding redox reactions, you not only gain a deeper understanding of chemistry but also see how it is intrinsically linked to the world around you!

Important Topics

Variation of Oxidation Number (NOX)

The oxidation number (NOX) is a key concept in redox reactions that indicates the real or imaginary charge that an atom would have if the electrons in a bond were fully transferred to the more electronegative atom. This number is crucial for identifying which atoms are oxidized or reduced in a reaction, as any increase in NOX indicates oxidation and any decrease indicates reduction.

• The NOX of an element in a free state is zero, while in a compound the NOX is equal to the charge of the ion.

• In compounds, the sum of the NOXs of all atoms must be zero for neutral compounds and equal to the charge of the ion in ionic compounds.

• The variation of NOX allows the identification of redox reactions, where the sum of the NOXs of the elements changes from one side of the equation to the other, indicating electron transfer.

Oxidizing and Reducing Agents

Oxidizing agents are substances that accept electrons from other substances, while reducing agents are substances that donate electrons. In a redox reaction, the reducing agent is oxidized, and the oxidizing agent is reduced. It is important to identify these agents because they are essential in determining the direction of the reaction and which substances are being oxidized or reduced.

• The reducing agent loses electrons, thus reducing another substance and itself being oxidized.

• The oxidizing agent gains electrons, thus oxidizing another substance and itself being reduced.

• The ability of an agent to oxidize or reduce other substances is measured by its standard reduction potential (Eº), with more positive values indicating stronger oxidizing agents and more negative values indicating stronger reducing agents.

Redox Equations

A redox equation is a chemical equation that shows the transfer of electrons between reactants that results in changes in oxidation numbers and the formation of products. Balancing redox equations is fundamental to ensuring that the law of conservation of mass and charge is respected. Methods such as the ion-electron method and the oxidation number method are used to balance these equations.

• The ion-electron method is useful for reactions in acidic solution, while the oxidation number method is more suitable for reactions in basic solution.

• Balancing a redox equation first involves dividing the reaction into oxidation and reduction reactions, balancing the number of atoms except for oxygen and hydrogen, and then balancing the oxygen using water and the hydrogen using hydrogen ions.

• Finally, the electrons are balanced by adding electrons to the reactants that gain and subtracting from the reactants that lose, and the overall equation is written by combining the oxidation and reduction reactions.

Key Terms

• Redox Reactions: Chemical reactions that involve the transfer of electrons between two reactants, where one is oxidized and the other is reduced.

• Oxidation Number (NOX): It is the real or imaginary charge of an atom in a molecule or ion, indicating how many electrons that atom shares or borrows in a bond.

• Oxidizing Agents: Substances that have the ability to accept electrons, oxidizing other substances.

• Reducing Agents: Substances that have the ability to donate electrons, reducing other substances.

To Reflect

• How are redox reactions important for our daily life, beyond classical examples such as metal corrosion and batteries?

• In what way can understanding redox reactions impact other areas of knowledge, such as biology and engineering?

• Think of an example of a redox reaction that you can observe at home or at school. Describe the reactants, products, and how you would identify the oxidizing and reducing agents.

Important Conclusions

• Redox reactions are essential for understanding how the transfer of electrons occurs between substances, being fundamental in biological, industrial, and daily processes.

• The variation of the oxidation number (NOX) is crucial for identifying which atoms are being oxidized or reduced in a reaction, helping to differentiate oxidizing and reducing agents.

• Balancing redox equations is not just an academic exercise, but a practical skill that ensures that the law of conservation of mass and charge is respected in any reaction.

To Exercise Knowledge

Choose an object at home that could undergo oxidation and identify the process that occurs in it. Try to balance the redox equation for the reduction reaction of copper (II) with metallic zinc, using the oxidation number method. Explore how redox reactions are involved in electricity production in a car battery, researching the role of sulfuric acid and the materials of the electrodes.

Challenge

Create a mini-project where you simulate the construction of a homemade battery using simple materials like lemons, nails, and copper wires. Document the process, including the chemical reactions that occur and how they fit into the concept of redox reactions.

Study Tips

• Use chemistry apps that allow you to visualize and practice balancing redox equations interactively.

• Form a study group with classmates to discuss and solve redox reaction problems, sharing different solving methods.

• Watch videos demonstrating redox reactions to visualize how they occur in practice and better understand the concepts discussed.