Chapter 19, Problem 14STP

To determine

To explain: The type of the given reaction in the photograph.

Answer to Problem 14STP

The chemical reaction between the magnesium and oxygen is as follows:

  $\text{2Mg}\left(\text{s}\right){\text{+O}}_{\text{2}}\left(\text{g}\right)\to \text{2MgO}$

The given reaction is exergonic because it releases the light during reaction and this burning reaction is an example of exothermic reaction because it releases heat.

Explanation of Solution

Introduction:

The free energy change is negative in the case of exergonic reaction while in the endergonic reaction, the free energy change is positive. Exothermic reactions are those reactions in which energy is released while endothermic reactions are those reactions in which energy is absorbed.

The given reactions involve release of energy therefore, this reaction is an exothermic reaction. Exergonic reactions and endergonic reactions are different from exothermic reaction or endothermic reactions in other kind such as, they release light rather than the heat energy. In the given photograph, when the magnesium is reacting with the oxygen, then spark or light is produced that means this reaction is an exergonic reaction. Since, the reaction takes place by burning thus, large amount of heat also releases, and it is an exothermic reaction.

Conclusion:

In the given photograph, the reaction is an example of exergonic reaction and an exothermic reaction.