Chapter 21, Problem 83GQ

Interpretation Introduction

Interpretation:

To calculate enthalpy change $\left({\Delta }_r{\text{H}}^{\circ }\right)$ of the given reaction.

Concept introduction:

The change of enthalpy to form one mole of a substance from its constituent elements when all the substances in the standard form is known as standard enthalpy of formation.

The standard enthalpy of reaction $\left({\Delta }_r{\text{H}}^{\circ }\right)$ in terms of standard enthalpy of formation $\left({\Delta }_f{\text{H}}^{\circ }\right)$ is written as,

${\Delta }_r{\text{H}}^{\circ }={\displaystyle \sum {\Delta }_f{\text{H}}^{\circ }{}_{\text{products}}-{\displaystyle \sum {\Delta }_f{\text{H}}^{\circ }{}_{\text{reactants}}}}$ (1)

The change of Gibbs free energy to form one mole of a substance from its constituent elements when all the substances in the standard form is known as standard Gibbs free energy of formation $\left({\Delta }_f{\text{G}}^{\text{°}}\right)$.

If the value of standard Gibbs free energy of reaction $\left({\Delta }_r{\text{G}}^{\circ }\right)$ is positive then the reaction is reactant favored. If the value of standard Gibbs free energy of reaction $\left({\Delta }_r{\text{G}}^{\circ }\right)$ is negative then the reaction is product favoured and spontaneous.