Chapter 10, Problem 15A

Interpretation Introduction

Interpretation : The statement corresponding to negative and positive sign of energy is to be stated.

Concept Introduction : According to thermodynamic law, the relation between change in the energy, heat and work done is given by the formula as shown below.

  $\Delta \text{E}=\text{q}+\text{w}$

Answer to Problem 15A

The negative sign of energy indicates that the reaction is an exothermic reaction, whereas positive sign indicates that the reaction is endothermic reaction.

Explanation of Solution

During a reaction the energy is either absorbed or energy is released. The reaction in which heat is released is called an exothermic reaction and change in enthalpy comes out to be negative, while the reactions in which the heat is absorbed are called endothermic reaction. The enthalpy change comes out to be positive for endothermic reactions.

Conclusion

The negative sign of energy indicates that the reaction is an exothermic reaction, whereas positive sign indicates that the reaction is endothermic reaction.