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Why is bond breaking endothermic?

Question:

Why is bond breaking endothermic?

Bond Breaking:

Many physical processes and chemical reactions involve absorption or emission (taking in or giving off) of heat. If the process gives off heat, it is called an exothermic process or reaction. If it takes in heat, it is called an endothermic process or reaction. In an endothermic process, the energy state of the product molecules or atoms is one of higher energy since energy is input into the system. Bond breaking is a situation that requires the input of energy making it an endothermic reaction.

Answer and Explanation:

The fact that bonds have formed indicates that there is increased stability (an advantage) for the atoms in a molecule to have made them. Bonds that are more stable are at a lower energy state than the free atoms or molecules. In order to break these bonds, one has to add energy that exceeds the stability molecules gained when the bonds formed. For instance, when carbon makes a single bond with another carbon, it will give off about 347 kJ/mol of energy when the bond form. In order to break that carbon-carbon single bond, one has to add at least 347 kJ/mol in order to overcome the stability the carbon atoms gained when the single molecular bond was made. So in all cases of bond breaking, one has to add some energy, whether it be a little or a lot, in order to overcome the bond energy (the stability) of the bonds in the molecules.


Learn more about this topic:

Bond Energy: Definition & Equation

from Chemistry: High School

Chapter 17 / Lesson 4
18K

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