A common way of initiating certain chemical reactions with light involves the generation of free halogen atoms in solution.If $\Delta$H for the reaction Cl₂(g)$\rarr$ 2Cl(g)is 242.8 kJ/mol, what is the longest wavelength of light that will produce free chlorine atoms in solution? A)246.3 nm B)349.3 nm C)465.2 nm D)492.6 nm E)698.6 nm

Question

Quizplus · Accepted Answer

The energy required to produce free chlorine atoms can be obtained from the given reaction enthalpy as follows:

ΔH = 242.8 kJ/mol = hc/λ - ECl-Cl

where h is the Planck constant, c is the speed of light, λ is the wavelength of light, and ECl-Cl is the bond dissociation energy of Cl-Cl bond in chlorine molecule.

Rearranging the equation, we get:

λ = hc/(ΔH + ECl-Cl)

Substituting the values, we get:

λ = (6.626*10^-34 J.s)(2.998*10^8 m/s)/(242,800 + 242) = 4.92*10^-7 m

Converting to nanometers, we get:

λ = 492.6 nm

Therefore, the longest wavelength of light that will produce free chlorine atoms in solution is 492.6 nm, which corresponds to option D.

A Common Way of Initiating Certain Chemical Reactions with Light Δ\DeltaΔ

A Common Way of Initiating Certain Chemical Reactions with Light $\Delta$