How is a spontaneous reaction defined in aqueous chemistry?

A spontaneous reaction in aqueous chemistry is defined as one that occurs without the need for external driving forces. This means that the reaction can take place naturally under the given conditions without the need for continuous energy input or manipulation.

Spontaneous reactions are driven by factors such as the increase in entropy or the change in free energy, and they can happen at varying rates. Importantly, spontaneity does not dictate that a reaction must release heat (exothermic), nor does it require the formation of gas as a product; rather, it is fundamentally about the reaction's tendency to proceed on its own.

This definition helps in understanding that spontaneous reactions can occur in various scenarios, including both exothermic and endothermic processes, as long as the overall free energy change is negative, meaning the products have lower free energy than the reactants. By recognizing this key aspect of spontaneity, students can better grasp the principles governing chemical reactions in different environments, especially in aqueous solutions.