• # question_answer Calculate the wavelength of light required to break the bond between two chlorine atoms in a chlorine molecule. The $CI-CI$bond energy is$243\,kJ\,mo{{l}^{-1}}$$(h=6.6\times {{10}^{-34}}J\,s;$$c=3\times {{10}^{8}}\,m/s;)$Avogadro's number $=6.02\times {{10}^{23}}\text{mo}{{\text{l}}^{-1}}$ A) $8.18\times {{10}^{-31}}m$         B) $6.26\times {{10}^{-21}}m$C) $4.91\times {{10}^{-7}}m$           D)  $4.1\times {{10}^{-6}}m$

Energy required to break one Cl-Cl bond $=\frac{\text{Bond}\,\text{enegy}\,\text{permole}}{\text{Avogadro }\!\!'\!\!\text{ s}\,\text{number}}$ $=\frac{243\times {{10}^{3}}}{6.02\times {{10}^{23}}}J$ Let the wavelength of the photon to cause rupture of one Cl-Cl bond be$\lambda$, $\lambda =\frac{hc}{E}=\frac{6.6\times {{10}^{8}}\times 6.02\times {{10}^{23}}}{243\times {{10}^{3}}}$ $=\frac{119.196}{243}\times {{10}^{-34}}\times {{10}^{31}}\times {{10}^{-3}}$ Therefore, $\lambda =4.91\times {{10}^{-7}}\,m.$ Hence, the correct option is [c].