Question

Radiation can be used for chemical reactions, principally to break bonds between atoms. From the list below identify the bond with the highest energy that can be broken by a photon of 1.17×1012 kHz frequency.

(a) H-H: 432 kJ/mol

(b) F-F: 159 kJ/mol

(c) H-F: 565 kJ/mol

(d) C-H: 413 kJ/mol

(e) O-H: 467 kJ/mol

Answer 1

E=h   where E=energy of the radiation

                    h=6.63*10^-34 m2 kg/s

                     =1.17×1012 kHz=1.17×10^15 Hz or s-1

E=(6.63*10^-34 m2 kg/s )*(1.17×10^15 s-1)

E =7.76 *10^-19 m2 kg s-2=7.76 *10^-19J

a)H-H: 432 kJ/mol= 432000 /6.022*10^23 J/molecule =7.17*10^4*10^-23 J/molecule=7.17*10^-19J/molecule

b)F-F: 159 kJ/mol=159000/6.022*10^23 J/molecule =2.64*10^4*10^-23 J/molecule=2.64*10^-19J/molecule

c)H-F: 565 kJ/mol=565000/6.022*10^23 J/molecule =9.38*10^4*10^-23 J/molecule=9.38*10^-19J/molecule

d)C-H: 413 kJ/mol=413000/6.022*10^23 J/bond =6.85*10^4*10^-23 J/bond=6.85*10^-19J/bond

e)O-H: 467 kJ/mol=467000/6.022*10^23 J/bond =7.75*10^4*10^-23 J/bond=7.75*10^-19J/bond

O-H:=7.75*10^-19J/bond < E photon =7.76 *10^-19J

So O-H the bond with the highest energy that can be broken by a photon of 1.17×1012 kHz frequency