Chapter 4, Problem 1FIO

Figure 4.5 Energy inputs and outputs in chemical reactions.

1. 1 Some reactions convert molecules with lower energy to molecules with higher energy, so they require a net energy input in order to proceed.
2. 2 Other reactions convert molecules with higher energy to molecules with lower energy, so they end with an energy release

Figure It Out: Which law of thermodynamics explains energy inputs and outputs in chemical reactions?

Summary Introduction

To determine: The law of thermodynamics that explains the energy inputs and outputs in chemical reaction.

Introduction: Thermodynamics is defined as the study of heat as well as other forms of energy. In the term thermodynamics, therm indicates heat and dynam indicates power. The first law of thermodynamics states that energy can neither be created nor destroyed. The second law of thermodynamics states that the energy can spread out spontaneously.

Explanation of Solution

The first law of thermodynamics explains the energy inputs and energy outputs in the chemical reactions. The first law of thermodynamics is also called as the law of conservation of energy and it states that the energy can neither be created nor destroyed. The total amount of energy that is present before and after conversion remains the same. If the energy present in reactants is less than the product, then the reaction will proceed only with the net energy input. If the energy of the reactant is higher than the product, the reaction ends with a net energy release.

In the given figure, a lower energy molecule is converted to a higher energy molecule and for the reaction to proceed, it requires net energy input. In the other reaction, higher energy molecule is converted to the lower energy molecule with a net energy release. Thus, the first law of thermodynamics explains the input and output of energy in the given chemical reactions.