Chapter 10.3, Problem 1RQ

Interpretation Introduction

Interpretation: The sign of enthalpy for an exothermic reaction needs to be determined.

Concept introduction: The process in which transfer of heat energy from system to surrounding takes place is termed as exothermic process and the process in which flow of energy from surrounding to system occur is known as endothermic process.

Answer to Problem 1RQ

For exothermic reaction, sign of enthalpy is negative.

Explanation of Solution

For a reaction occurring under conditions of constant pressure, change in enthalpy $\left(\Delta H\right)$ is equal to the energy that flows as heat.

  $\Delta H_p=\text{Heat}$

The subscript p indicates that the process occurred in the condition of constant pressure. In exothermic reaction energy flows out from the system as heat so, the sign of enthalpy is negative.

Conclusion

The positive sign of enthalpy indicates endothermic reaction.