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.
Create a free account to view solution
View Solution FreeMore Thermochemistry Questions
The specific heats of iodine vapours and solid are 0.031 and 0.055 cal/g, respectively. If the enthalpy of sublimation o...The molar heat capacities at constant pressure (assumed constant with respect to temperature) at A,B and C are in ratio ...The most exothermic ‘ordinary’ chemical reaction for a given mass of reactants is 2H(g) → H2(g), where ΔE = 103 kcal. Th...The word standard in molar enthalpy change implies...Which of the following statement is incorrect about internal energy ?...