Calculating bond energy
Calculating bond energy
Worked example 4
Embedded Files
Bond breaking is an endothermic process.
Bond making is an exothermic process.
Overall energy change = breaking bonds total energy – making bonds total energy
Worked example 4:
The reaction between methane and oxygen occurs as shown.
methane + oxygen --> carbon dioxide + water
CH4 + 2O2 --> CO2 + 2H2O
The displayed formulae below show more clearly the bonds in each molecule involved in the reaction.
Calculate the total energy changes involved in the process of breaking and forming these bonds using the bond energies from the table below. (6)
Step 1. Calculate energy taken in when breaking bonds (1)
(4 x C - H) + (2 x O = O)
(4 x 412) + (2 x 498) =
Step 2. Calculate energy released from making bonds (1)
(2 x C = O) + (4 x H - O)
(2 x 805) + (4 x 464) =
Step 3: Calculate total energy change (1)
Overall energy change = breaking bonds total energy – making bonds total energy
Overall energy change =
Overall energy change = kJ/mol
Step 4: Explain if the reaction is an endothermic or an exothermic process. (3)
Overall energy change = kJ/mol
the energy released from making bonds is higher than energy taken in when breaking bonds
so, overall more energy has been lost to the surrounding
the reaction is exothermic.
Page updated
Google Sites
Report abuse