Periodic Classification and Periodic Properties 2 Question 10

«««< HEAD

10. The first ionisation potential of $\mathrm{Na}$ is $5.1 \mathrm{eV}$. The value of electron gain enthalpy of $\mathrm{Na}^{+}$will be

======= ####10. The first ionisation potential of $\mathrm{Na}$ is $5.1 \mathrm{eV}$. The value of electron gain enthalpy of $\mathrm{Na}^{+}$will be

3e0f7ab6f6a50373c3f2dbda6ca2533482a77bed (a) $-2.55 \mathrm{eV}$

(b) $-5.1 \mathrm{eV}$

(c) $-10.2 \mathrm{eV}$

(d) $+2.55 \mathrm{eV}$

(2013 Main)

Show Answer

Answer:

Correct Answer: 10. (b)

Solution:

$$ \begin{aligned} \mathrm{Na} & \longrightarrow \mathrm{Na}^{+}+e^{-} \text {First IE } \ \mathrm{Na}^{+}+e^{-} & \longrightarrow \mathrm{Na} \end{aligned} $$

Electron gain enthalpy of $\mathrm{Na}^{+}$is reverse of (IE)

Because reaction is reverse so $\Delta H(e q)=-5.1 \mathrm{eV}$