Physical Chemistry - Energetics (Paper 2)

Question 1

how would you draw an energy level diagram for an exothermic reaction?

Answer 1

reactants are drawn higher than products as they have more energy
enthalpy change is drawn as a downwards arrow, as reactants are losing energy as heat

Question 2

how would you draw an energy level diagram for an exothermic reaction?

Answer 2

reactants are drawn lower than products as they have less energy
enthalpy change is drawn as an upwards arrow, as reactants are gaining energy

Question 3

what type of processes are bond breaking and bond making?

Answer 3

bond breaking is endothermic as breaking bonds needs energy
bond making is exothermic as when new bonds are made energy is released

Question 4

how do you calculate enthalpy change with bond energies?

Answer 4

Enthalpy change, ΔH = Energy needed to break all the bonds - Energy released to make all the new bonds