Calculating Energy Changes

Question 1

What is BENDOMEX used to remember?

Answer 1

Breaking bonds is endothermic, making bonds is exothermic

Question 2

Energy change in a reaction

Answer 2

Energy change in a reaction = (total energy needed to break the bonds in the reactants) - (total energy released when bonds in the products are formed)

Question 3

Bond energy

Answer 3

The amount of energy needed to break a bond (bonds between different elements all have a specific amount of energy)

Question 4

Calculating energy change when given the bond energy

Answer 4

1) balance equation
2) write underneath how many of these bonds there are in each reactant and product
3) energy change = (total reactant energy) - (total product energy)

Question 5

If the energy change is negative, the reaction is…

Answer 5

Exothermic, as more energy is released making the bonds in the products than is required to break the bonds in the reactants

Question 6

If the energy change is positive, the reaction is…

Answer 6

Endothermic, as more energy is needed to break the bonds in the reactants than is released when the bonds in the products are made