the energy change of reactions

what happens to bonds during a chemical reaction?

old bonds are broken, and new bonds are formed

what type of process is bond breaking and why?

endothermic, because energy must be supplied to break bonds

what type of process is bond formation and why?

exothermic, because energy is released when new bonds are formed

what happens in an exothermic reaction in terms of bond energy?

the energy released by forming bonds is greater than the energy used to break them

what happens in an endothermic reaction in terms of bond energy?

the energy used to break bonds is greater than the energy released by forming them

what is bond energy?

the amount of energy needed to break a particular bond, which varies depending on the compound

how can bond energies be used in calculations?

they help calculate the overall energy change in a reaction

how do you calculate the overall energy change in a reaction?

energy required to break bonds minus energy released when new bonds form

what are the three steps in bond energy calculations?

1. find energy needed to break original bonds - multiply the bond energy by the number of bonds of that type, and then add up all the values to get the total energy needed to break all bonds

2. find energy released by forming new bonds - multiply the bond energy by the number of bonds of that type, and then add up all the values to get the total energy released when new bonds form

3. subtract energy released from energy required - energy change = total energy to break bonds - total energy to form bonds