Chemical Energy Flashcards
What is enthalpy
Its a measure of chemical energy in a substance
What are exothermic reactions
Reactions that release heat energy
Enthalpy change is negative
What are endothermic reactions
Reactions that take in heat energy
Are enthalpy change is positive
What is the enthalpy of combustion
The enthalpy of combustion is the energy change when one mole of a substance burns completely in oxygen
Is enthalpy of combustion endothermic or exothermic
Always exothermic
What does Hess’s law state
States that the enthalpy change for a chemical reaction is independent of the route taken.
To use bond enthalpies what state must substances be in
Gaseous state
What is molar bond enthalpy
The energy required to break one mole of bonds (to give separate atoms) in a diatomic molecule
What is the MEAN (molar) bond enthalpy
The average energy needed to break one mole of bonds, for a bond that occurs in a molecule with more than 2 atoms and or exists in a number of compounds.
Are bonds being broken/formed endothermic or exothermic
Bonds broken are are endothermic and bonds formed are exothermic
