An iodine molecule dissociates into atom after absorbing light of wavelength `4500`Å. If quantum of radiation is absorbed by each molecule calculate the kinetic energy of iodine (Bond energy of `I_(2)` is `240`` kJ mol^(-1))`

Explanation

Bond energy per molecule of `I_(2) = (240 xx 1000J)/(6.022 xx 10^(23)) = 3.985 xx 10^(-19)J`
Energy absorbed `= (hc)/(lamda) = ((6.626 xx 10^(-34) Js) (3 xx 10^(8) ms^(-1)))/(4500 xx 10^(-10)m) = 4.417 xx 10^(-19)J`
The difference of energy absorbed and energy used for dissociation of bond in `I_(2)` gives the kinetic energy one `I_(2)` molecule.
`:.` K.E. of one `I_(2)` molecule `= (4.417 xx 10^(-19) - 3.985 xx 10^(-19)) J = 4.32 xx 10^(-20)J`
`:.` K.E. of one iodine atom `= (4.32 xx 10^(-20))/(2) J = 2.16 xx 10^(-20)J`