JEE Mains Model Paper 9

Enthalpy of formation of NH3
= − 46 kJ / mole
∴ N2+3H2 → 2NH3
ΔHf = −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) − 6x = − 46 × 2
∴ x = 352 kJ / mol