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E n t h a l p y. E n t h a l p y. Enthalpy. E n t h a l p y. reactants. Enthalpy. E n t h a l p y. reactants. Enthalpy. products. E n t h a l p y. reactants. ∆H. Enthalpy. products. E n t h a l p y. For some reactions, ∆H cannot be measured. E n t h a l p y.
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Enthalpy Enthalpy
Enthalpy reactants Enthalpy
Enthalpy reactants Enthalpy products
Enthalpy reactants ∆H Enthalpy products
Enthalpy For some reactions, ∆H cannot be measured.
Enthalpy If the reaction happens in steps, the total ∆H is equal to the sum of ∆H for each step. reactant Enthalpy intermediate product final product
Enthalpy Standard enthalpies of formation have been measured for many different compounds.
Enthalpy Standard enthalpies of formation have been measured for many different compounds. For any element in its standard state, ∆Hf = 0.
Enthalpy CH4 + 2O2 → CO2 + 2H2O
Enthalpy CH4 + 2O2 → CO2 + 2H2O ∆Hf(products) - ∆Hf(reactants) ∆Hf(reaction)
Enthalpy CH4 + 2O2 → CO2 + 2H2O Standard enthalpies of formation:
Enthalpy CH4 + 2O2 → CO2 + 2H2O Standard enthalpies of formation: -75 + 0 → -394 + -286
Enthalpy CH4 + 2O2 → CO2 + 2H2O Standard enthalpies of formation: -75 + 2(0) → -394 + 2(-286)
Enthalpy CH4 + 2O2 → CO2 + 2H2O Standard enthalpies of formation: -75 + 2(0) → -394 + 2(-286) -75 → -680
Enthalpy CH4 + 2O2 → CO2 + 2H2O Standard enthalpies of formation: -75 + 2(0) → -394 + 2(-286) -75 → -680 ∆Hf(reaction) = -605
Homework: Page 512 problems 31, 34, 35