Given reaction:
N2 + 3Cl2 → 2NCl3
Energy change = Bonds broken - bonds formed
ΔHrxn = Bond energy[ N≡N + 3*Cl-Cl] - Bond energy [6*N-Cl]
= [945 + 3(240)] - [6(200)] = 465 kJ/mol
Now, atomic mass of Cl = 35.5 g/mol
Given mass of Cl = 85.3 g
# moles of Cl = 85.3/35.5 = 2.403 moles
ΔH corresponding to the above moles of Cl would be
= 2.403 moles * 465 kJ/ 1 mole = 1117.4 J
Ans: The reaction enthalpy for 85.3 g of chlorine = 1.12 kJ
