Heats of Formation.

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Presentation transcript:

Heats of Formation

Definition ΔHf – energy change associated with the formation of compound from its constituent elements Standard Heat of Formation - ΔHfº - heat of formation of a material in its standard state (most stable form) See Appendix Four (pg. A19)

Examples What is the equation and heat of formation for: a) acetylene (C2H2) b) silver chloride ● ΔHfº for an element is zero

Calculating Heats of Reaction Δ Hrxn = ∑nΔHfº(product) - ∑mΔHfº(reactant) Find the heat of reaction for: C6H12O6 + 6O2 → 6CO2 + 6H2O

Example Compare the quantity of heat produced by the combustion of 1.00 g of glucose with that produced by 1.00g of sucrose.

Example The standard enthalpy change for the reaction: CaCO3 → CaO + CO2 is 178.1 kJ. From the value of ΔHfº for CaO and CO2, calculate the ΔHfº for CaCO3 .