Questions

(1) lifetime of molecule in an excited electronic state is 10 ^ -10 s. The uncertainty in the energy eV approx is

uncertainty in energy can be calculated by using the formula
delta E * delta t > h bar / 2
here h bar = h/2pi
therefore
 uncertainty in energy delta E = h/4 pi delta t
put he values and you will get the answer as 5.275*10^-25 J = 3.29 *10^-6 eV