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Hess's Law definitions

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  • Hess's Law
    A principle stating that the total enthalpy change for a reaction is the sum of the enthalpy changes for each step, regardless of the reaction pathway.
  • Thermochemical Equation
    A chemical equation that includes the enthalpy change, showing the energy absorbed or released during a reaction.
  • Enthalpy of Reaction
    The heat energy change associated with a chemical reaction, often represented as delta H.
  • Delta H
    A symbol representing the enthalpy change for a reaction, indicating whether heat is absorbed or released.
  • Coefficient
    A number placed before a chemical formula in an equation, indicating the relative amount of each substance involved.
  • Reaction Intermediate
    A substance produced and consumed in multi-step reactions, appearing on both sides of partial equations and canceling out.
  • Partial Reaction
    An individual step in a multi-step process, each with its own enthalpy change, contributing to the overall reaction.
  • Standard Enthalpy Value
    A measured enthalpy change under standard conditions, used to calculate overall enthalpy changes in reactions.
  • Product
    A substance formed as a result of a chemical reaction, appearing on the right side of a chemical equation.
  • Reactant
    A starting substance in a chemical reaction, found on the left side of a chemical equation.
  • Sign Reversal
    A change in the direction of a reaction that causes the enthalpy value to switch from positive to negative or vice versa.
  • Kilojoule
    A unit of energy commonly used to express enthalpy changes in chemical reactions.
  • Multi-step Reaction
    A process involving several sequential reactions, each with its own enthalpy change, summed to find the total change.
  • Cancellation
    The process where identical substances on both sides of combined equations are removed, simplifying the overall reaction.
  • Overall Reaction
    The final chemical equation obtained after combining all partial reactions and canceling intermediates.