In solid NaCl, the equilibrium separation between neighboring Na+ and Cl- ions is 0.283 nm. Calculate the coulombic energy between Na+ and Cl???? at this distance. Give your answer in each of J, eV, and kJ/mol units.

Respuesta :

Explanation:

It is given that r = 0.283 nm. As 1 nm = [tex]10^{-9} m[/tex].

Hence, 0.283 nm = [tex]0.283 \times 10^{-9} m[/tex]

  • Formula for coulombic energy is as follows.

             [tex]U_{coulomb} = -1.748 \frac{e^{2}}{4 \pi \epsilon_{o} r}[/tex]

where,   e = [tex]1.6 \times 10^{-19}[/tex] C

            [tex]\epsilon_{o}[/tex] = [tex]8.85 \times 10^{-12}[/tex]

          [tex]U_{coulomb} = -1.748 \frac{(1.6 \times 10^{-19}^{2}}{4 \times 3.14 \times 8.85 \times 10^{-12} \times 0.283 \times 10^{-9}}[/tex]

                         = [tex]1.423 \times 10^{-18} J[/tex]

  • As 1 eV = [tex]1.6 \times 10^{-19} J[/tex]

So,       1 J = [tex]\frac{1 eV}{1.6 \times 10^{-19}}[/tex]

Hence,    U = [tex]\frac{1.423 \times 10^{-18} J}{1.6 \times 10^{-19} J}[/tex]

                   = 8.9 eV

  • Also,   1 J = [tex]\frac{10^{-3} kJ}{6.022 \times 10^{23}mol}[/tex]

                = [tex]1.67 \times 10^{-27}[/tex] kJ/mol

Therefore, U = [tex]1.423 \times 10^{-18} J \times 1.67 \times 10^{-27}[/tex] kJ/mol

                     = [tex]2.37 \times 10^{-45} kJ/mol[/tex]

Q&A Education