What is Gibbs Free Energy?
For a simple definition, Gibbs free energy can be described as
A measure of the amount of energy available to do work.
Gibbs free energy is used in chemistry to help determine and predict ahead of time whether a chemical process is spontaneous or non-spontaneous.
You might be wondering what’s the advantage of that. There are many applications in life that we need advance knowledge what to expect. For example in the manufacturing of products – if you have no clue which direction your process is going, then you might produce something totally unexpected and waste a lot of resources.
In a spontaneous process, it happens automatically. You might have to start off the process with a little activation energy and the rest will take care of itself. A good example of a spontaneous process is combustion – the burning of substances to produce heat and energy. You may have to light the substance first (giving it activation energy) but once the substance burns, it continues by itself.
In a non-spontaneous process, a continuous energy input is necessary for the reaction to proceed in a certain direction.
A good example is photosynthesis, a process in which plants use to make glucose. Photosynthesis requires energy in the form of sunlight to drive chemical reactions. Therefore at night when it’s dark, photosynthesis does not work.
Spontaneous vs Non-spontaneous process
|A spontaneous process – no continuous energy input from external source is necessary to run the process||A non-spontaneous process – a continuous energy input is necessary to run the process|
The Gibb’s Free Energy is simply a method of telling whether a chemical process will take place spontaneously or non-spontaneously.
- The Gibbs free energy calculates the amount of energy available in a system to do work like carrying out a chemical reaction.
- Gibbs free energy is only applicable for systems under constant temperature and pressure.
- The Gibbs calculation allows you to determine whether a process is spontaneous or not.
- Gibbs calculation uses the relationship between Ethalpy and Entropy in a system to determine the spontaneity of a process.
HOW TO DETERMINE IF A REACTION IS SPONTANEOUS
For notes on spontaneity, please click here >>
Gibbs Free Energy is the energy associated with a chemical reaction that can be used to do work.
∆H – Enthalpy is the change of heat in a system due to chemical reaction measured in joules
∆S –Entropy is the measure of energy dispersal in j/k
∆G – Gibbs free energy
∆Gsystem = ∆Hsystem – T∆Ssystem
- If ∆G is negative – spontaneous reaction.
- If ∆G is positive – non spontaneous reaction.
Equation representing the reaction occurring under standard condition (298K and 1atm)