## 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.

## Spontaneous Process

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.

## Non-spontaneous Process

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

Gibbs Free Energy is the energy associated with a chemical reaction that can be used to do work.

## ∆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)

## Now Gibbs free energy is Enthalpy minus Entropy.

Example Calculation

Go here to see an example of Gibb’s Free Energy calculation for the Haber Process of ammonia manufacturing >>

## 1 thought on “Understanding Gibbs Free Energy”

1. Anonymous says:

Superb..it just easy to learn and understand