Strength of a covalent bond

In summary, the person wanted to estimate the temperature needed to break a covalent bond of strength 1.70 eV and questioned if comparing thermal energy to the bond strength would give the correct temperature. They calculated a temperature of 11000K, but realized their mistake and corrected it to be closer to 20000K. The conversation then focused on the complexity of the process, considering factors such as time and other variables.
  • #1
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2
Hey!

I want to estimate the temperature needed to break a covalent bond of strength 1.70 eV. Whould it be correct to compare the thermal energy [tex]k_B T[/tex] to the bond strength and find the temperature needed to make the thermal energy larger than the bond strength? I get a temperature of about 11000K, which seems a little high to me.
 
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  • #2
Repetit said:
Hey!

I want to estimate the temperature needed to break a covalent bond of strength 1.70 eV. Whould it be correct to compare the thermal energy [tex]k_B T[/tex] to the bond strength and find the temperature needed to make the thermal energy larger than the bond strength? I get a temperature of about 11000K, which seems a little high to me.
1. 1.7eV should be closer to 20,000K (room temperature is about 25meV).

2. Given enough time, you can break ONE covalent bond of 1.7eV strength even at room temperature. Assume the molecular temperatures follow a Boltzmann distribution; if the mean temperature is 300K, what fraction of molecules have a temperature of 20,000K? So, clearly, this is a question of kinetics.

3. In the limit of an infinite supply of the reactant molecule or continuously removed product (conditions far removed from equilibrium), the time taken to make the required quantity of product (ie: break the required number of covalent bonds) is given by the (likely first order) rate constant.

4. Note for instance, that thermal decomposition of water is usually carried out (industrially) at temperatures which are about an order of magnitude smaller than the bond energy; under quasi-equilibrium conditions the yield is typically about a percent.
http://adsabs.harvard.edu/abs/1983IJHE...8..675L
 
Last edited:
  • #3
Thanks for the reply! Your are right, the temperature is closer to 20,000K, I made a dumb mistake when calculating the value.

I believe things are not as simple as I wanted them to be, because time and other factors play an important role as well.
 

1. What is a covalent bond?

A covalent bond is a type of chemical bond where two atoms share one or more pairs of electrons to achieve stability.

2. How is the strength of a covalent bond determined?

The strength of a covalent bond is determined by the difference in electronegativity between the two atoms involved. The greater the difference, the stronger the bond.

3. What factors can affect the strength of a covalent bond?

The strength of a covalent bond can be affected by the types of atoms involved, the distance between the atoms, and the orbital overlap between the atoms.

4. How does the strength of a covalent bond compare to other types of bonds?

Covalent bonds are generally stronger than ionic bonds and weaker than metallic bonds. They also have a higher strength compared to hydrogen bonds.

5. Why is the strength of a covalent bond important in chemical reactions?

The strength of a covalent bond determines the stability of a molecule and how easily it can undergo chemical reactions. Stronger bonds are more difficult to break and therefore, chemical reactions may require more energy to occur.

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