BRAINCAKECalculating Enthalpy Changes from Bond Enthalpies
| bond | mean bond enthalpy kJmol-1 | ||
| N≡N | 945 | ||
| H-H | 436 | ||
| N-H | 391 |
N2(g) + 3H2(g) → 2NH3(g)
The enthalpy change is calculated from
total bond enthalpies reactants - total bond enthalpies products.
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Key terms in this lesson
- Enthalpy
- A measure of the total energy of a chemical system.
- Enthalpy change
- The heat energy that is transferred between the system and its surroundings during a process carried out at constant pressure.
More in Enthalpy
- Accuracy of Experimental Value
- Determining the Enthalpy Change of a Reaction
- Cooling Curves
- Average Bond Enthalpy
- Limitations of Bond Enthalpy Calculations
- Hess's Law
- Determination of Enthalpy Change of a Reaction from Enthalpies of Formation Using Hess's Law
- Determination of Enthalpy Change of a Reaction from Enthalpies of Combustion using Hess's Law
All 19 lessons in Enthalpy · All OCR AS-level Chemistry topics