Respuesta :
Explanation:
The given data is as follows.
      Energy needed for 1 mole = 279.7 kJ = [tex]279.7 \times \frac{1000 J}{1 kJ}[/tex]
                            = 279700 J
Therefore, energy required for 1 atom will be calculated as follows.
            [tex]\frac{279700}{6.022 \times 10^{22}}[/tex]
             = [tex]4.645 \times 10^{-19} J[/tex]
As relation between energy and wavelength is as follows.
         E = [tex]\frac{hc}{\lambda}[/tex]
where, Â Â h = planck constant = [tex]6.62 \times 10^{-34} Js[/tex]
        c = speed of light = [tex]3 \times 10^{8} m/s[/tex]
      [tex]\lambda[/tex] = wavelength
Therefore, putting given values into the above formula as follows.
         E = [tex]\frac{hc}{\lambda}[/tex]
   [tex]4.645 \times 10^{-19} J[/tex] = [tex]\frac{6.62 \times 10^{-34} Js \times 3 \times 10^{8} m/s}{\lambda}[/tex] Â
       [tex]\lambda[/tex] = [tex]4.28 \times 10^{-7} m[/tex] Â
or, Â Â Â Â Â Â Â Â Â Â Â Â = [tex]428 \times 10{-9}[/tex] m
               = 428 nm
Thus, we can conclude that the maximum wavelength of light that can remove an electron from an atom on the surface of lithium metal is 428 nm.
