Chapter 6, Problem 1VCQ

Figure 6.8 Look at each of the processes shown, and decide if it is endergonic or exergonic. In each case, does enthalpy increase or decrease, and does entropy increase or decrease?

Summary Introduction

To write:

To discuss exergonic or endergonic reaction in given conditions.

Introduction:

Synthesis of complex molecules from simpler ones by using energy is called the anabolic process. It is an endergonic process. In contrast, the breakdown of complex molecules into simpler ones is the catabolic process. Energy is released in this process, it is an exergonic process.

Explanation of Solution

The processes given in the figure can be classified as exergonic or endergonic as follows:

1. A compost pile decomposing is an exergonic process as energy is being released. Enthalpy increases due to energy release and entropy also increase as large molecules broken into smaller ones.
2. A chick developing from a fertilized egg requires energy, so this is an endergonic reaction. Due to the absorption of energy enthalpy decreases. Entropy decreases as large molecules are formed from the small molecules.
3. Sand art is being destroyed which is an exergonic reaction. Enthalpy remains same as there is no change in the total energy, but entropy increases as smaller molecules combine to form large molecules.
4. A ball rolling down the hill is an exergonic reaction as it releases energy and enthalpy decreases. But there is no change in entropy.

Conclusion

An endergonic reaction is that reaction which requires energy and exergonic reaction are those reactions which release energy. Enthalpy is the total energy of the system whereas entropy measures the disorder within the system.