Define spontaneity in chemical reactions and ex... - SS1 Chemistry Energy Changes in Chemical Reactions Question

Spontaneity in chemical reactions refers to the tendency of a reaction to occur without any external influence. It is determined by the energy changes that take place during the reaction. Gibbs free energy (ΔG) is a thermodynamic quantity that measures the energy available to do useful work in a system and is directly related to the spontaneity of a reaction.

 

The relationship between spontaneity and Gibbs free energy is given by the following equation:

 

ΔG = ΔH - TΔS

 

Where:

- ΔG is the change in Gibbs free energy

- ΔH is the change in enthalpy

- T is the temperature in Kelvin

- ΔS is the change in entropy

 

For a reaction to be spontaneous at a given temperature, the change in Gibbs free energy must be negative (ΔG < 0). This indicates that the reaction is energetically favourable, and the reaction will proceed spontaneously in the forward direction. Conversely, if ΔG is positive (ΔG > 0), the reaction is nonspontaneous, and an input of energy is required for the reaction to occur.

 

The significance of Gibbs free energy in determining spontaneity lies in its ability to account for both enthalpy and entropy changes in a system. ΔH represents the change in heat energy, while TΔS represents the change in the energy associated with the disorder or randomness of the system (entropy). The combination of these factors determines the overall change in Gibbs free energy.