For The Reaction
21N2(g)+23H2(g)→NH3(g);ΔHf∘=−46KJmol−1
ΔHf∘=−46=∑B.E−∑B.E
Reactants Product
∑B.E=∑B.E+46
Product Reactants
=21(712)+23(436)+46
= 356 + 654 + 46 = 1056
Averge B.E for N-H Bond =31056=352KJmol−1
The standard enthalpy of formation ofNH3 is −46.0kJ/mol. If bond enthalpy of H2 is −436kJ/mol and that of N2 is −712kJ/mol , the average bond enthalpy of N−H bond in NH3 is :
Held on 9 Apr 2014 · Verified 6 Jul 2026.
−964kJ/mol
−1102kJ/mol
+1056kJ/mol
+352kJ/mol
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