Chemical Energy

Question 1

What is enthalpy?

Answer 1

A measure of the chemical energy in a substance (measured in kJ).

Question 2

What is enthalpy of combustion?

Answer 2

the energy change when one mole of the substance burns completely in oxygen.

Question 3

State Hess’s Law.

Answer 3

• “the enthalpy change for a reaction depends on the initial and final states of the reaction and is independent of the route the reaction occurs.”
• this means that no matter the route taken, the enthalpy change will always be the same for a reaction.

Question 4

What is molar bond enthalpy?

Answer 4

• the energy required to break one mole of bonds in a diatomic molecule.
• mean molar bond enthalpy is the energy required to break one mole of bonds that occur in compounds (not diatomic).