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NEET Chemistry
QUESTION #7408
Question 1
What is the electron gain enthalpy of Na⁺, given that the first ionisation energy of Na is 5.1 eV?
Correct Answer Explanation
Key concept:
\(\text{Na} \to \text{Na}^+ + e^-\): requires IE₁ = +5.1 eV (energy absorbed)
Electron gain enthalpy of Na⁺ is the reverse process:
\(\text{Na}^+ + e^- \to \text{Na}\): releases the same energy
\(\Delta_{\text{eg}}H(\text{Na}^+) = -5.1\) eV
This follows Hess's law — the reverse process has equal and opposite enthalpy.
\(\text{Na} \to \text{Na}^+ + e^-\): requires IE₁ = +5.1 eV (energy absorbed)
Electron gain enthalpy of Na⁺ is the reverse process:
\(\text{Na}^+ + e^- \to \text{Na}\): releases the same energy
\(\Delta_{\text{eg}}H(\text{Na}^+) = -5.1\) eV
This follows Hess's law — the reverse process has equal and opposite enthalpy.
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