Bond energy and activation energy

In summary, during a reaction, the energy required to break the bonds of the reactants is the same as the activation energy required to bring the reactants to the transition state. Once the transition state is reached, the bonds are broken and the reaction can proceed.
  • #1
sgstudent
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3
Is the energy required to break the bonds of a compound in order for the reaction to occur (bond energy) the same as activation energy? Thanks for the help! :smile:
 
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  • #2
Do you need to break the bonds entirely to reach the transition state?
 
  • #3
Borek said:
Do you need to break the bonds entirely to reach the transition state?

I think so, when we do the calculating it is enthalpy to break bonds+enthalpy to form bonds. When we calculate it the bond breaking part is the bond energy so all the bonds have to break. So
I'm guessing that the
activation energy is the energy required to break the
bonds. But then again, when a substitution reaction only the chlorine gas' and one C-H bond gets broken. So is the activation energy the energy to break only certain bonds?Thanks!
 
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  • #4
What is a transition state?
 
  • #5
Borek said:
What is a transition state?

from what I read I think its the intermediate part of the reaction meaning its the reactants st the peak of the activation energy 'mountain'. So not all the bonds are broken? Because in the reactions I see are pike H2+O2-->2H2O so the transition state all the bonds are broken. But when I see my sister's O level notes there are questions with organic reactions so I don't thing its possible for all the bonds to break. But she still calculated it such that all the bonds are broken so I'm white confused here... thanks for tbe help!
 
  • #6
sgstudent said:
I think so, when we do the calculating it is enthalpy to break bonds+enthalpy to form bonds.
I think you are picturing a process like this:

reactants --> (bond breaking) --> transition state = individual species with all relevant bonds broken --> (bond formation) --> products

But does it have to follow that sequence?
 
  • #7
BromoethaneSN2reaction-small.png
 
  • #8
Gokul43201 said:
I think you are picturing a process like this:

reactants --> (bond breaking) --> transition state = individual species with all relevant bonds broken --> (bond formation) --> products

But does it have to follow that sequence?

I'm guessing that not all the bonds have to break since in some reaction only certain bonds are required to be broken like in the CH4+Cl2 case. But then the part that scares me is on finding the activation energy since when such reaction occurs only the involved bonds are the activation energy. Is there a way to determine it? When I draw out the full structural formula it gives some insights but still its quite difficult...thanks for the help guys!
 
  • #9
sgstudent said:
then the part that scares me is on finding the activation energy

Experimentally, or through QM only, you can't find it from typical thermodynamic data. And this is nothing unusual. Or perhaps I should put it differently - it is rather unusual to be able to calculate activation energy just from the thermodynamical data describing bond energies.
 
  • #10
Borek said:
Experimentally, or through QM only, you can't find it from typical thermodynamic data. And this is nothing unusual. Or perhaps I should put it differently - it is rather unusual to be able to calculate activation energy just from the thermodynamical data describing bond energies.

Hi Borek I suddenly started thinking about this again and I read the chemguide explanation. So what I got from it was that when the reactants collide with activation energy and correct orientation, the old bonds are partially broken at simultaneously new bonds are partially formed. But what happens after that transition state? Will more energy be absorbed to continue breaking those bonds?

Thanks and sorry for the super long wait before this reply its because I just thought about it after revising and reading up on some online notes. Thanks :)
 

1. What is bond energy and how is it related to chemical reactions?

Bond energy is the amount of energy required to break a chemical bond between two atoms. This energy is often used as a measure of the strength of a bond. In chemical reactions, bonds are broken and formed, and the difference in bond energies between the reactants and products determines the overall energy change of the reaction.

2. How is bond energy different from activation energy?

While bond energy is the energy required to break a bond, activation energy is the minimum amount of energy needed to start a chemical reaction. In other words, bond energy is a property of a specific bond, while activation energy is a property of a chemical reaction.

3. How does bond energy affect the rate of a chemical reaction?

The higher the bond energy, the stronger the bond and the more energy is required to break it. This means that reactions involving strong bonds will have higher activation energies and will proceed at a slower rate compared to reactions involving weaker bonds.

4. Can bond energy and activation energy be measured experimentally?

Yes, both bond energy and activation energy can be measured experimentally using various techniques such as calorimetry and spectroscopy. These measurements can provide valuable information about the nature and strength of chemical bonds and the energy changes involved in chemical reactions.

5. How can bond energy and activation energy be altered?

Bond energy can be altered by changing the types of atoms involved in a bond, such as using different elements or substituting functional groups. Activation energy, on the other hand, can be altered by changing reaction conditions such as temperature, pressure, and the presence of catalysts. These changes can affect the rate and outcome of a chemical reaction.

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