Chemical Thermodynamics Question 86

Question: The first ionization energy for Li is 5.4 eV and electron affinity of Cl is 3.61eV. The $ \Delta H $ (in kJ/mol) for the reaction $ Li(g)+Cl(g)\to L{{i}^{+}}+C{{l}^{-}} $ is (if resulting ions do not combine with each other) $ (1,eV=1.6\times {{10}^{-19}}J) $ [MP PMT 2000, 03]

Options:

A) 70

B) 100

C) 170

D) 270

Show Answer

Answer:

Correct Answer: C

Solution:

First ionization potential of $ Li=5.4eV $ Electron affinity of $ Cl=3.61eV $ We have $ \Delta H=I.P.-E.A. $

$ =5.4-3.61=1.80eV=1.80\times 1.6\times {{10}^{-22}}kJ $

$ \Delta H=2.86\times {{10}^{-22}}kJ, $ for 1mol Avogadro-s number $ =6.02\times 10^{23} $ . $ \Delta H=2.86\times {{10}^{-22}}\times 6.02\times 10^{23}=170,kJ/mole. $



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