Module 1

Module 1—Thinking Energy

Lesson Summary

 

In Lesson 8 you considered the following question:

• How are standard molar enthalpies of formation used to determine the enthalpy change associated with chemical reactions?

You learned about standards and reference points used to study energy changes. The reference point for standard molar enthalpies of formation states that the potential energy of elements in their most stable form at SATP is 0 kJ/mol. You also learned how to interpret values for standard molar enthalpies of formation to assess the thermal stability of compounds. You used these values much in the same way you used Hess’ law, to calculate a reaction enthalpy.

 

Lesson Glossary

 

reference energy state: a reference point at which the potential energy of the elements in their most stable form at SATP is defined as zero

 

standard enthalpy of formation: the enthalpy change calculated from the measurements of a formation reaction under standard conditions

 

thermal stability: the tendency of a compound to resist decomposition when heated

 

The lower a compound's standard enthalpy of formation, the more stable the compound.

Chemistry 30 © 2009 Alberta Education