The energy required to break one mol of Cl-Cl bonds in ${\mathrm{Cl}}_2$ is $242 \mathrm{K} \mathrm{J} {\mathrm{mol}}^{-}$. The largest wavelength of light capable of breaking a single Cl-Cl bond is: $\left(c=3\times {10}^8{\mathrm{ms}}^{-}\right.$and $\left.{\mathrm{N}}_{\mathrm{A}}=6.02\times {10}^{23}{\mathrm{mol}}^{-}\right)$