Spontaneous and Non-spontaneous Processes

There are two types of chemical reactions that occur in the environment, which are spontaneous reactions and non-spontaneous reactions. The occurrence of spontaneous reactions takes place on their own when a certain set of conditions are fulfilled, although the process of non-spontaneous reaction requires external energy to be provided. The change in Gibbs Free Energy for spontaneous reactions is negative, thus energy is released in the form of heat to the surroundings during the process of spontaneous reaction, whereas the change in energy for Gibbs Free Energy is positive in case of non-spontaneous reaction. The occurrence of these reactions absorb energy from the surrounding environment. This can be related to the fact that spontaneous reactions are exergonic in nature and the non-spontaneous reactions are endergonic in nature. The basic difference between both these processes is that spontaneous reactions release free energy from the system making the reaction stable and the non-spontaneous reactions increase the total energy present in the system by absorbing energy from the external environment.

Spontaneous reactions are referred as those type of chemical reactions, where the occurrence of reaction takes place without the application of any external force whereas non-spontaneous reactions are those type of chemical reactions that occur through the external application of energy for the process to complete. Spontaneous reactions are favorable because they release energy out of the system but the non-spontaneous reactions are unfavorable because they absorb energy from the surroundings. The energy released during spontaneous processes makes the system more stable and the absorption of energy into the system during the non-spontaneous processes increase the total energy present within the system. The total energy of the products in case of spontaneous reactions is less than the reactants and the total energy of the products in non-spontaneous reactions is more than that of the reactants. Spontaneous processes have a negative enthalpy and the non-spontaneous processes have a positive enthalpy, spontaneous processes increase the entropy and the non-spontaneous processes decrease the entropy of the system. Spontaneous processes takes place at a rapid rate and non-spontaneous processes occur at a much slower pace.

The occurrence of spontaneous reactions refer to chemical reactions, which occur without the application of external force, the two forces which drives the chemical reaction in a system are enthalpy and entropy. Enthalpy is thermodynamic property, which is the sum total of internal energy that is added to the product of pressure and volume of the system. Non-spontaneous reactions are those chemical reactions that require input of energy to process. Enthalpy and entropy, both prefer the reactants, which makes the reactions more stable than the products.

Dispersal of Matter and Energy for Spontaneous Process

The concept towards prediction of spontaneity let us consider an isolated system that consist of two flasks connected through a closed valve. Initially, there is a presence of an ideal gas on the left side and a vacuum towards right. Once, the valve is opened, the expansion of gas spontaneously expands for filling both the flasks. The definition of pressure-volume is done when the pressure in a vacuum is zero.

Due to the isolation of system, there is no exchange of heat from the surroundings. The first law of thermodynamics states that there is no change in the total internal energy of the system as a result of the process. The spontaneity in this process is not a result of a change of the energy that is accompanied in the process, whereas the force driving the process relates to a greater and more uniform dispersal of matter, which occurs during the process of expansion of the gas. Initially, the system had one flask containing matter and the other flask had nothing, after the completion of the process, the matter is distributed widely and uniformly. The isolated system consisting of an ideal gas in one flask connected by a closed valve to a second flask that has vacuum, when the valve is opened there is an even distribution between the flasks.

Let us consider two objects at different temperature, when these objects come in contact, the flow of heat is spontaneous from the object that is hotter to the colder one, this is directly related to the change in thermal energy. These two systems has no net gain or loss of heat energy, instead the thermal energy is evenly distributed between the systems, which results in uniform dispersal of energy between the available systems. These two processes describe an important factor to determine the spontaneity of the process that results in the dispersal and distribution of matter and energy, that uniformly distributes matter and energy in case of spontaneous process