Heats of Formation

1
Heats of Formation
2
Definition

• ?Hf energy change associated with the formation
  of compound from its constituent elements
• Standard Heat of Formation - ?Hfº - heat of
  formation of a material in its standard state
  (most stable form)
• See Appendix Four (pg. A21)

3
Examples

• What is the equation and heat of formation for
• a) acetylene
• b) silver chloride
• ? ?Hfº for an element is zero

4
Calculating Heats of Reaction

• ? Hrxn ?n?Hfº(product) - ?m?Hfº(reactant)
• Find the heat of reaction for
• C6H12O6 6O2 ? 6CO2 6H2O

5
Example

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

6
Example

• The standard enthalpy change for the reaction
  
  CaCO3 ? CaO CO2
  is 178.1 kJ. From the value of
  ?Hfº for CaO and CO2, calculate the ?Hfº for
  CaCO3 .