Chapter 9, Problem 9.105QP

(a)

Interpretation Introduction

Interpretation:

Bond enthalpy of $F^{2-}$ ion has to be calculated using the given data.

Concept Introduction:

$\Delta H°$ refers to change in enthalpy.  Change in enthalpy in a reaction and bond energy (BE) are related as,

    $\text{ΔH°}\text{=}\text{ΣBE(reactants)-ΣBE(products)}$

Change in enthalpy in a reaction and enthalpy of formation are related by the formula,

    $\Delta H_{rxn}^{°}=\Sigma \Delta H_f^{°}(product)-\Sigma \Delta H_f^{°}(reac\tan t)$

Where,

    $\begin{array}{l}\Delta H_{rxn}^{°}=\text{ enthalpy change in reaction}\\ \Delta H_f^{°}(product)=\text{ enthalpy or heat of formation of product}\\ \Delta H_f^{°}(reac\tan t)=\text{ enthalpy or heat of formation of }reac\tan t\end{array}$

Hess’s law is applied to calculate the enthalpy changes in a reaction.  According to Hess’s law – “The overall enthalpy change of a reaction is equal to the sum of the enthalpy changes involving in each and every individual steps in the reaction.”  Thus if a reaction involves ‘n’ steps then enthalpy change $\Delta H°$ of the reaction is,

  $\Delta H°=\Delta {\text{H}}_1^{°}+\Delta {\text{H}}_2^{°}+\Delta {\text{H}}_3^{°}\mathrm{....}+\Delta {\text{H}}_n^{°}$

(b)

Interpretation Introduction

Interpretation:

The difference in bond enthalpies of $F_2^{-}$ and $F_2$ has to be explained.