Hess's Law and Reaction Energy
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These flashcards cover Hess's law, reaction energy calculations, and related concepts.
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10 Terms
Hess's Law
A principle stating that the total enthalpy change of a reaction is the sum of the enthalpy changes of individual steps.
Reaction Energy Formula
The formula for calculating the reaction energy is given by ext{DH}^ ext{rxn} = ext{Σ} m ext{DH}'_f( ext{products}) - ext{Σ} ext{DH}'_f( ext{reactants}).
Formation Values
Standard enthalpy of formation values used to calculate the energy change in a reaction.
Coefficient Multiplication
In the reaction energy calculation, multiply each enthalpy of formation by its corresponding coefficient in the balanced equation.
Product Sum
Add the enthalpy values of the products after multiplying by their coefficients.
Reactant Sum
Add the enthalpy values of the reactants after multiplying by their coefficients.
Energy Subtraction
The final step in calculating reaction energy involves subtracting the sum of the reactant energies from the sum of the product energies.
Positive ΔH_f
A normal positive value for enthalpy of formation indicates that products are formed.
Negative ΔH_f
A reverse or negative value for enthalpy of formation indicates that reactants are broken.
Total Reaction Energy
The sum of the calculated energies from products and reactants gives the total reaction energy.
