Chapter 9, Problem 9.88QP

Interpretation Introduction

Interpretation:

The wavelength of light required to carry out the given reaction should be calculated.

Concept Introduction:

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 involved in the reaction.” Thus if a reaction involves ‘n’ steps then enthalpy change $\Delta H°$ of the reaction is,

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

Change in enthalpy in a reaction and bond energy (BE) are related as follows,

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

$\Delta H°$ refers to change in enthalpy.

Energy and wavelength $\left(\lambda \right)$ are related by the formula as follows,

$\lambda =\frac{hc}{E}$

Where,

$\begin{array}{l}\lambda =wavelength\\ h=Planck\text{'}s\text{constant}\\ c=velocityoflight\\ E=Energy\end{array}$