ThermochemistryHard
Question
Boron exists in different allotropic forms. All allotropic form contains icosahedral units (icosahedral is a regular shape with 12 corners and 20 faces) with boron atoms at all 12 corners and all bonds are equivalent. Calculate the heat evolved at constant pressure (in kJ/mole) of boron atom undergoing the above change if the bond dissociation enthalpy of B–B bond is 300 kJ/mol.
Options
A.500
B.750
C.1500
D.900
Solution
There is 2.5 B-B bond per B atom. Hence, ΔH = –2.5 × 300 = –750 kJ/mole of Boron.
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