Understanding Hess' Law: C2H4 + H2O -> C2H5OH

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SUMMARY

This discussion focuses on Hess' Law as it applies to the reaction C2H4 (g) + H2O (g) -> C2H5OH (g), with a calculated enthalpy change (ΔH) of -89 kJ. The user attempts to reconcile their calculation with a textbook answer of +3 kJ, asserting their calculation is correct. The discrepancy highlights the importance of correctly applying Hess' Law to determine the overall enthalpy change in chemical reactions.

PREREQUISITES
  • Understanding of Hess' Law
  • Basic knowledge of enthalpy changes (ΔH)
  • Familiarity with chemical reaction equations
  • Ability to perform thermodynamic calculations
NEXT STEPS
  • Review Hess' Law applications in thermodynamics
  • Study enthalpy change calculations for multi-step reactions
  • Learn about standard enthalpy of formation
  • Explore discrepancies in thermodynamic data interpretation
USEFUL FOR

Chemistry students, educators, and anyone studying thermodynamics or chemical reaction energetics will benefit from this discussion.

terryds
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Homework Statement


2ppitrr.png


Homework Equations



Hess' Law

The Attempt at a Solution



C2H4 (g) + H2O (g) -> C2H5OH (g) ΔH = - 46 kJ
C2H5OH(g) -> C2H5OH(l) ΔH = - 43 kJI think the ΔH is - 46 - 43 = - 89

However, the book says that the answer is A. +3 kJ
How come that be?
 
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It can't be, that's how. Your answer is right.
 
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