1) The first ionisation potential of Na is 5.1 eV. The value of electron gain enthalpy of Na+ will be A) -2.55 eV B) -5.1 eV C) -10.2 eV D) +2.55 e V Answer: Option BExplanation:$Na\rightarrow Na^{+}+e^{-}$ First IE $ Na^{+}+e^{-}\rightarrow Na$ Electron gain enthalpy of Na+ is reverse of (IE) Because reaction is reverse so $\triangle H(eq)=-5.1eV$
