Chemistry Regents Practice Test 2025 – Complete Prep Resource

An oxidation-reduction reaction, commonly referred to as a redox reaction, is fundamentally characterized by the transfer of electrons between reactants. In these reactions, oxidation refers to the process where a substance loses electrons, while reduction refers to the gain of electrons by another substance. This electron transfer results in changes to the oxidation states of the elements involved.

For example, in a typical redox reaction, one reactant is oxidized while another is reduced. This interchange plays a crucial role in various chemical processes, including combustion, respiration, and corrosion. Therefore, understanding that the core function of redox reactions is the shifting of electrons helps clarify their significance in chemistry.

As such, the correct definition encapsulates the essence of oxidation-reduction reactions, distinguishing them from the other types of reactions mentioned. The other options pertain to different chemical concepts: proton exchange characterizes acid-base reactions, energy emission relates to exothermic reactions or certain types of luminescence, and the principle of constant mass concerns the conservation of mass in physical and chemical processes.