Wavelength to break a bond

Worked example

Find the maximum photon wavelength able to cleave a bond of energy 392 kJ mol⁻¹.

1. 1. Energy per mole of photons: solve for λ

   $\lambda = \dfrac{N_\mathrm{A}hc}{E_\mathrm{m}}$

   = 305.2 nm

Answer: λ = 305 nm

Method

Per photon E = D/N_A, so λ = N_A hc / D. Higher bond energy needs shorter wavelength.

Formulas used

• Energy per mole of photons

  $E_\mathrm{m} = \dfrac{N_\mathrm{A}hc}{\lambda}$

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