What characterizes a redox reaction?

A redox reaction is characterized by the transfer of electrons between species. In these types of reactions, one species undergoes oxidation (losing electrons) while another undergoes reduction (gaining electrons). This transfer is fundamental to the concept of redox chemistry because it involves changes in oxidation states.

For example, in a typical redox reaction, you might see a metal react with a nonmetal, where the metal donates electrons to the nonmetal. This process is crucial for understanding various chemical processes, including combustion, respiration, and corrosion.

The other options do not capture the essence of a redox reaction. While reactions with water can lead to acid formation, they do not inherently involve electron transfer. Similarly, the formation of a gas and a precipitate can occur in many types of reactions, not just redox. Lastly, the idea of equal participation of reactants does not align with the nature of electron transfer, which distinctly marks one species as losing electrons (oxidation) and another as gaining them (reduction).