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