It takes 242./kjmol to break a chlorine-chlorine single bond. calculate the maximum wavelength of light for which a chlorine-chlorine single bond could be broken by absorbing a single photon. round your answer to 3 significant digits.

The working equation for this is the Planck's Law:

E = hc/λ
where
E is the energy
h is the Planck's constant equal to 6.62607004×10⁻³⁴ m²·kg / s
c is the speed of light equal to 3×10⁸  m/s
λ is the wavelength

Assuming 1 mol of Cl-Cl bond,

242 kJ * 1000 J/1 kJ = (6.62607004×10⁻³⁴ m²·kg / s)(3×10⁸  m/s)/λ
λ = 8.214×10⁻³¹ m

The teacher is mostly talking about the distillation of a mixture