$I_2$molecule dissociates into atoms after absorbing light of 4500 $\AA$ . If one quantum of energy is absorbed by each molecule, the KE of iodine atoms will be        

                                                          

Energy given to $l_2$molecule = $\frac{hc}{\lambda }$

$=\frac{6.626\times -34\times 3\times {10}^8}{4500\times {10}^{-10}}$

$=4.4\times {10}^{-19}J$

Energy of  molecule   $l_2$ molecule   $=240\times {10}^{3}J/mol$

$=\frac{240\times {10}^3}{6.0-23\times {10}^{23}}J/atom$

$=3.98\times {10}^{-19}J/atom$

$KE=(4.4\times {10}^{-19)}-(3.98\times {10}^{-19})$

$=0.42\times {10}^{-19}J/atom$

$KEofIatoms$

                        $=\frac{0.42}{2}\times {10}^{-19}=0,21\times {10}^{19}$