Concept explainers
Bond energies such as those in Table 5.1 are sometimes found by “working backward” from heats of reaction. A reaction is carried out, and the heat absorbed or evolved is measured. From this value and known bond energies, other bond energies can be calculated. For example, the energy change associated with the combustion of formaldehyde (H2CO) is −465 kJ/mol.
Use this information and the values found in Table 5.1 to calculate the energy of the C═O double bond in formaldehyde. Compare your answer with the C═O bond energy in CO2 and speculate on why there is a difference.
Interpretation:
The carbon – oxygen double energy has to be calculated and compare with the bond energy in
Concept introduction:
Endothermic reaction: When the heat energy was absorbed by the system from the surrounding is called endothermic reaction
Exothermic reaction: When heat energy or light energy was unconfined to the surrounding from the system is called exothermic reaction.
Net energy change is calculated from the difference between the total energy absorbed in breaking bonds and total energy released in forming bonds.
Explanation of Solution
The given is shown below,
Bonds broken in the reactants are given below:
Therefore,
Bonds formed in the products are given below:
Therefore,
The value for
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