Electron gain enthalpy of $Cl$ is $- 349 kJ mo l^{- 1}$ . Take 1 eV per atom = $96.5 kJ mo l^{- 1}$ and $h c = 1240 eV nm$ . The longest wavelength of light that can detach an electron from $Cl X^{-} (g)$ is closest to

A $171 nm$
B $343 nm$
C $686 nm$
D $3.5 nm$

Answer: B

Detaching the electron needs +349 kJ/mol = 349/96.5 = 3.62 eV per ion. Wavelength = 1240/3.62 = 343 nm. Halving or doubling the energy gives 686 or 171 nm.

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Electron gain enthalpy of Cl is −349 kJ mol−1. Take 1 eV per atom = 96.5 kJ mol−1 and hc=1240 eV nm. The longest wavelength of light that can detach an electron from ClX−(g) is closest to

Answer: B

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Electron gain enthalpy of $Cl$ is $- 349 kJ mo l^{- 1}$ . Take 1 eV per atom = $96.5 kJ mo l^{- 1}$ and $h c = 1240 eV nm$ . The longest wavelength of light that can detach an electron from $Cl X^{-} (g)$ is closest to