Final answer:
When delta G is positive, it indicates an endergonic reaction that absorbs energy and is non-spontaneous. The reaction will require an input of energy to proceed. The spontaneity of such reactions is dictated by the enthalpy and entropy changes of the system.
Step-by-step explanation:
When considering a chemical reaction, the term delta G refers to the change in Gibbs free energy of the system. If delta G is positive (positive delta G), this indicates that free energy is absorbed by the reaction, and it is known as an endergonic reaction. In these cases, the products have more free energy than the reactants, signifying that the reaction requires an input of energy to proceed. The direction of such a reaction is non-spontaneous or spontaneous in the reverse direction. Here, the reaction would only proceed if energy is supplied to the system.
To calculate delta G, the enthalpy change (delta H) is adjusted for the temperature-scaled entropy change (T delta S) using the equation delta G = delta H - T delta S. Entropy (delta S) is a measure of the disorder or randomness in a system, and enthalpy (delta H) is the total heat content. Variables in this equation, including enthalpy (delta H), entropy (delta S), and temperature (T, in Kelvin), determine the spontaneity of the reaction.
Furthermore, for a reaction to be spontaneous at all temperatures, the enthalpy must be negative and entropy must be positive. However, if the enthalpy is positive and entropy is negative, delta G will always be positive, indicating that the reaction is non-spontaneous in any condition.