The minimum energy needed to dissociate iodine molecules, I2, is 151 kJ/mol. What is the wavelength of photons (in nm) that supplies this energy, assuming each bond dissociated by absorbing one photon?
1 Answer
Explanation:
Equations this solution applied:

#N=n*N_A# where#N# is the quantity of#n# moles of particles and#N_A=6.02*10^23*"mol"^(1)# is the Avagordoro's number 
The Planck's Law
#E=h*f# where#E# is the energy of a single photon of frequency#f# and#h# is the Planck's Constant,#h=6.63 × 10^(34)* "m"^2* "kg" *"s"^(1)= 6.63*10^(34) color(blue)("J")*"s"# [1] 
#lambda=v/f# where#lambda# is the wavelength of a wave or an electromagnetic (EM) radiation of frequency#f# .
From the question, breaking
where
Thus it takes
to break a single iodine molecule.
Apply the Planck's Law to find the maximum frequency of the EM radiation capable of breaking one such molecule:
*Make sure that you get the unit that corresponds to the quantity after canceling out corresponding pairs. Here we are expecting
Assuming
Sources:
1. Units ("dimensions") of the Planck's Constant: https://www.askiitians.com/forums/GeneralPhysics/findthedimensionofplanckconstanthfromthee_74309.htm