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. $
