Question

What do we mean when we say that the transfer of electrons can be the "driving force" for a reaction? Give an example of a reaction where this happens.

Short answer

The transfer of electrons refers to the movement of electrons from one atom or compound to another, playing a vital role in chemical reactions. When the transfer of electrons is the primary force driving a reaction, it is characterized as an oxidation-reduction (redox) reaction. A classic example of a redox reaction is the reaction between sodium metal (Na) and chlorine gas (Cl_2) to form sodium chloride (NaCl): \[2Na + Cl_2 \rightarrow 2NaCl\] In this reaction, sodium is oxidized (losing an electron), while chlorine is reduced (gaining an electron). This electron transfer is the driving force behind the reaction, releasing energy and allowing for the formation of a stable ionic compound, sodium chloride.

Step-by-step solution

Understanding Electron Transfer

The transfer of electrons in a chemical reaction refers to the movement of electrons from one atom or compound to another. This process plays a vital role in determining how these substances interact with each other. When the transfer of electrons is the primary force driving a reaction, the reaction is characterized as an oxidation-reduction reaction (also called a redox reaction). Oxidation occurs when an atom or compound loses electrons, while reduction is the process of gaining electrons. In a redox reaction, there is always a substance being oxidized (losing electrons) and another substance being reduced (gaining electrons). This transfer of electrons can release or consume energy, making it the "driving force" for a reaction since it can determine whether the reaction is exothermic (releasing energy) or endothermic (absorbing energy).

Example of a Redox Reaction

A classic example of a redox reaction involving electron transfer is the reaction between sodium metal (Na) and chlorine gas (Cl_2) to form sodium chloride (NaCl, which is common table salt): \[2Na + Cl_2 \rightarrow 2NaCl\] In this reaction, sodium loses an electron to become positively charged (oxidized), while chlorine gains an electron to become negatively charged (reduced). This electron transfer is the driving force behind the reaction, as it releases energy and allows for the formation of a stable ionic compound (sodium chloride).