Chapter U5, Problem SII3RE

Interpretation Introduction

Interpretation: If iron nails are left outside, they will rust according to the reaction:

  $\text{4Fe}\left(s\right)+3{\text{O}}_2\left(g\right)\to 2{\text{Fe}}_{\text{2}}{\text{O}}_{\text{3}}\left(s\right)$

This reaction not appears to release light and heat to be described. 

Concept introduction: Thermodynamics is the analysis of heat transfer. Heat transfer direction is always from a hotter substance to colder one.

Answer to Problem SII3RE

Given reaction occurs very slowly. Thus without being noticed energy of this reaction is lost to the environment.

Explanation of Solution

Given reaction is as follows:

  $\text{4Fe}\left(s\right)+3{\text{O}}_2\left(g\right)\to 2{\text{Fe}}_{\text{2}}{\text{O}}_{\text{3}}\left(s\right)$

This reaction occurs very slowly. Thus without being noticed energy of this reaction is lost to the environment. Due to this reason given reaction not appears to release light and heat.

Conclusion

During a chemical change amount of energy transferred per gram or per mole is commonly called the heat of reaction $\left(\Delta \text{H}\right)$ . Without being noticed heat of the given reaction is lost to the environment because the reaction occurs very slowly.