ThermochemistryMedium
Question
If the bond dissociation energies of XY, X2 and Y2 (all diatomic molecules) are in the ratio of 1:1:0.5 and ᐃfH for the formation of XY is -200 kJ mole-1. The bond dissociation energy of X2 will be
Options
A.100 kJ mole-1
B.200 kJ mole-1
C.300 kJ mole-1
D.400 kJ mole-1
Solution
(None of the options is correct.)
XY → X(g) + Y(g) ; ᐃH = + a kJ /mole ........(i)
X22X ; ᐃH = + a kJ/mole ........(ii)
Y22Y ; ᐃH = + 0.5 a kJ/mole ........(ii)
× (ii) + × (iii) - (i), Gives
Y2 → XY ; ᐃH = 
kJ / mole
- a = - 200
a = 800.
XY → X(g) + Y(g) ; ᐃH = + a kJ /mole ........(i)
X22X ; ᐃH = + a kJ/mole ........(ii)
Y22Y ; ᐃH = + 0.5 a kJ/mole ........(ii)
× (ii) + × (iii) - (i), Gives Y2 → XY ; ᐃH = kJ / mole - a = - 200 a = 800.
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