Energy is calculated by molecule dividing energy by mole by Avogadro's number (6.022*10^23)
941kJ=9.41*10^5 J
so energy by molecule
E= 9.41*10^5/6.022*10^23=1.563*10^-18 J
Wavelength (w) given by E=hc/w
where, E = energy
h = planks constant (6.6262 x 10-34 J·s)
c = speed of light (3 x 10^8 m/s )
So,
w= hc/E
= (6.6262*10^-34)*(3*10^8) /1.563*10^-18
= 127.2 Nm
Longest wavelength of radiation =127.2 Nm