Q. What is the value of electron gain enthalpy of Na⁺ if IE₁ of Na = 5.1 eV?
A) +2.55 eV
B) +10.2 eV
C) –5.1 eV
D) –10.2 eV
Explanation
[Solution from source] Na⁺ + e⁻ → Na is exactly the reverse of Na → Na⁺ + e⁻ (IE₁ = 5.1 eV), so energy is released and ΔegH = −5.1 eV. +2.55 eV or ±10.2 eV come from wrongly halving or doubling the ionisation energy. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.