Question

When we balance an oxidation-reduction equation, the number of electrons lost by the reducing agent must ________ the number of electrons gained by the oxidizing agent.

Short answer

When we balance an oxidation-reduction equation, the number of electrons lost by the reducing agent must \(equal\) the number of electrons gained by the oxidizing agent.

Step-by-step solution

Understand redox reactions

In a redox reaction, one species (the reducing agent) loses electrons and gets oxidized, while another species (the oxidizing agent) gains electrons and gets reduced. The exchange of electrons between these species is the driving force behind redox reactions.

Balancing redox reactions

To balance redox reactions, we need to ensure that the number of electrons lost by the reducing agent is equal to the number of electrons gained by the oxidizing agent. This is because electrons cannot be created or destroyed; they can only be transferred from one species to another. So, the number of electrons lost must be the same as the number of electrons gained to maintain the overall charge balance in the reaction.

Fill in the blank

In summary, the relationship between the number of electrons lost by the reducing agent and the number of electrons gained by the oxidizing agent in a redox reaction is that they must be equal. Therefore, the answer is: When we balance an oxidation-reduction equation, the number of electrons lost by the reducing agent must "equal" the number of electrons gained by the oxidizing agent.

Key concepts

Redox Reactions

Understanding redox reactions is crucial for mastering chemistry. A redox, or oxidation-reduction, reaction is a type of chemical process where one substance, known as the reducing agent, donates electrons, undergoing oxidation, while another substance, the oxidizing agent, accepts these electrons, undergoing reduction. This simultaneous exchange is essential for a myriad of processes, ranging from generating electricity in batteries to the metabolic reactions in our bodies.

In essence, to balance a redox reaction, we meticulously account for all atoms and their charges, ensuring a stable reaction. This balance is not only pivotal for academic exercises but also for practical applications in lab settings and industry. Let's consider an example:

• In the reaction between hydrogen gas and oxygen to form water (\(2H_2 + O_2 \rightarrow 2H_2O\)), hydrogen (\(H_2\)) loses electrons, thus is oxidized, and oxygen (\(O_2\)) gains electrons, thus is reduced.

To balance this, hydrogen and oxygen atoms are counted and the electron transfer is equalized ensuring the reaction maintains the law of conservation of mass and charge.

Oxidation and Reduction

The Terms 'Oxidation' and 'Reduction'

Initially, the terms 'oxidation' and 'reduction' were coined with oxygen transfer in mind, but they've extended to cover electron transfer. Oxidation refers to a process where a substance loses electrons, commonly associated with a gain in oxygen or loss of hydrogen. Conversely, reduction pertains to the gain of electrons, often accompanied by a loss of oxygen or gain in hydrogen.

Oxidation Numbers

To keep track of these changes, we assign 'oxidation numbers' to atoms in molecules and ions. When balancing a redox reaction, observing the changes in these numbers becomes a reliable indicator of whether oxidation or reduction has occurred. If a substance's oxidation number increases, it is oxidized; if it decreases, it is reduced. By understanding this, students can dissect complex reactions to deduce the flow of electrons and balance equations accordingly.

Electron Transfer in Chemistry

Electron transfer underpins the very nature of chemical reactions, especially redox reactions. It's a microscopic exchange where electrons jump from one atom to another. This leads to changes in the structure and energy of the molecules involved, producing new substances.

The process of electron transfer is not random; it follows precise rules pertaining to the movement of electrons from higher to lower energy states, ultimately seeking stability. The species that loses electrons (oxidized) typically moves towards a more positive oxidation state, while that which gains electrons (reduced) moves to a more negative state. This electrifying dance between atoms not only defines the identity of the molecules formed but also governs the energy changes that accompany chemical reactions, enabling the various forms of work that these reactions can perform.