FC20: Enthalpy 2

Question 1

What is bond enthalpy

Answer 1

it is the energy needed to break one mole of a particular type of bond in molecules in the gaseous state

Question 2

Why are bond enthalpies usually average bond enthalpy values

Answer 2

bond enthalpies are averaged out over a range of compounds because the bond enthalpy for a particular bond may be different in different molecules

Question 3

What is the formula for calculating enthalpy change of a reaction

Answer 3

sum of bond enthalpies in reactants - sum of bond enthalpies in products

Question 4

What does Hess’s Law state

Answer 4

that the enthalpy change of a reaction is independent of the route taken, provided the starting and final conditions are the same