The standard enthalpy of formation of NH 3 is − 46.0 kJ mol − 1 . If the enthalpy of formation of H 2 from its atoms is − 436 kJ mol − 1 and that of N 2 is − 712 kJ mol − 1 , the average bond en

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The standard enthalpy of formation of NH 3 ​ is − 46.0 kJ mol − 1 . If the enthalpy of formation of H 2 ​ from its atoms is − 436 kJ mol − 1 and that of N 2 ​ is − 712 kJ mol − 1 , the average bond enthalpy of N − H bond in NH 3 ​ is

TestHub · Accepted Answer

Enthalpy of formation of NH 3 ​ = − 46 kJ / mole ∴ N 2 ​ + 3 H 2 ​ → 2 NH 3 ​ Δ H f ​ = − 2 × 46 kJ mol Bond breaking is endothermic and Bond formation is exothermic Assuming ' x ' is the bond energy of N − H bond ( kJ mol − 1 ) ​ ∴ 712 + ( 3 × 436 ) − 6 x = − 46 × 2 ∴ x = 352 kJ / mol ​

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