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Iodine molecule dissociates into atoms after absorbing light of 4500$A^{\circ}$ .If one quantum of radiation is absorbed by each molecule,calculate the kinetic energy of iodine atoms (Bond energy of $I_2=240KJmol^{-1}$)

$\begin{array}{1 1}(a)\;0.216\times 10^{-19}J&(b)\;0.312\times 10^{-10}J\\(c)\;1.345\times 10^{-19}J&(d)\;0.114\times 10^{-14}J\end{array}$

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Energy given to $I_2$ molecule $=\large\frac{hc}{\lambda}$
$\Rightarrow \large\frac{6.626\times 10^{-34}\times 3\times 10^8}{4500\times 10^{-10}}$
$\Rightarrow 4.417\times 10^{-19}J$
Energy used for breaking up of $I_2$ molecule=$\large\frac{2.4\times 10^3}{6.023\times 10^{23}}$
$\Rightarrow 3.984\times 10^{-19}J$
Energy used in importing kinetic energy to two I atoms
$\Rightarrow [4.417-3.984]\times 10^{-19}J$
Kinetic energy/iodine atom =$[(4.417-3.984)/2]\times 10^{-19}$
$\Rightarrow 0.216\times 10^{-19}J$
Hence (a) is the correct answer.
answered Jan 15, 2014 by sreemathi.v

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