Hessscher Satz-Rechner
Berechnen Sie die Reaktionsenthalpie mithilfe des Hessschen Satzes.
Overall ΔH
-300.0 kJ
Overall ΔH vs ΔH of Step 1
Formel
## Hess's Law ### Principle **ΔH_total = ΔH₁ + ΔH₂ + ΔH₃ + ...** Enthalpy is a state function, so the total enthalpy change depends only on the initial and final states, not the pathway. You can add up enthalpy changes of intermediate steps to find the overall change. Reverse a reaction: change sign of ΔH. Multiply coefficients: multiply ΔH by the same factor.
Lösungsbeispiel
Three-step pathway: Step 1 = -200 kJ, Step 2 = -150 kJ, Step 3 = +50 kJ.
- 01ΔH_total = ΔH₁ + ΔH₂ + ΔH₃
- 02ΔH_total = -200 + (-150) + 50
- 03ΔH_total = -300 kJ
Häufig Gestellte Fragen
What is Hess's Law?
Hess's Law states that the enthalpy change of a reaction is the same regardless of the number of steps. This is because enthalpy is a state function.
How do I reverse a reaction step?
Reverse the reaction and change the sign of ΔH. If the forward reaction has ΔH = -200 kJ, the reverse has ΔH = +200 kJ.
Why is Hess's Law useful?
Many reactions can't be measured directly in a calorimeter. Hess's Law lets you calculate ΔH from reactions that can be measured.
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