4NH₃₍g₎ + 3O₂₍g₎ = 2N₂₍g₎ + 6H₂O₍g₎ ΔrH₁ = -1266kJ
2H₂₍g₎ + O₂₍g₎ = 2H₂O₍g₎ ΔrH₁ = -483kJ
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N2 + 3H2 = 2NH3 ΔrH
adunam algebric ecuatiile.... :
4NH₃₍g₎ + 3O₂₍g₎ = 2N₂₍g₎ + 6H₂O₍g₎ ΔrH₁ = -1266kJ
2H₂₍g₎ + O₂₍g₎ = 2H₂O₍g₎ ΔrH₁ = -483kJ /x(-3)
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N2 + 3H2 = 2NH3 ΔrH /x(-2)
legea lui Hess spune ca
ΔrH = ΔrH1 + ΔrH2
=> (-2)ΔrH = ΔrH1 + (-3)ΔrH2
=> (-2)ΔrH = -1266 + (-3)(-483) /(-)
=> 2ΔrH = 1266 - 3x483
=> ΔrH = -91,5 kJ/mol
