Chapter 9, Problem 9.69QP

Interpretation Introduction

Interpretation:

The standard enthalpy of formation of ${\text{F}}_{\left(\text{g}\right)}$ has to be calculated.

Concept Introduction:

The measure of stability of molecule is bond enthalpy.  The change in enthalpy is related in breaking a specific bond of 1 mole of gaseous molecule.  In solids and liquids bond enthalpies are affected by neighboring molecules.  There is possibility to predict the enthalpy of reaction using the average bond enthalpies.  Energy is always needed for the breaking of chemical bonds and release of energy always takes place with the formation of chemical bonds.  The enthalpy of reaction is estimated by counting the total number of broken bonds and bonds formed in a reaction.

The enthalpy of reaction in gas phase is given by,

$\text{ΔH°=}{\displaystyle \sum {\text{BE}}_{\text{(reactants)}}}\text{-}{\displaystyle \sum {\text{BE}}_{\left(\text{products}\right)}}$

Where,

BE= Bond enthalpy and ${\displaystyle \sum \text{=}}$ summation

Standard enthalpy of formation:

The change in enthalpy that is associated with the formation of one mole of a substance from its related elements being in standard state is called standard enthalpy of formation (${\text{ΔH}}_{\text{f}}\text{°}$).  The standard enthalpy of formation is used to determine the standard enthalpies of compound and element.

The standard enthalpy of reaction is the enthalpy of reaction that takes place under standard conditions.

 The equation for determining the standard enthalpies of compound and element can be given by,

${\text{ΔH°}}_{\text{reaction}}\text{=}{\displaystyle \sum {\text{nΔH°}}_{\text{f}}\text{(products)}}\text{-}{\displaystyle \sum {\text{mΔH°}}_{\text{f}}\text{(reactants)}}$

To calculate: The ${\text{ΔH°}}_{\text{f}}$ of ${\text{F}}_{\left(\text{g}\right)}$