Bonding energy in compounds

  • #1

Main Question or Discussion Point

I have been researching on the bonding energies of different compounds, and for example, for CO2 it is 1600kJ/mole, 1600kJ/44g, or ~36.37kJ/g of energy required to split the carbon dioxide into carbon and oxygen. Furthermore, I transformed the amount of energy required in kJ to degrees celsius, and got 845.2 Cº for splitting 44g (or 1 mole), or 19.15 Cº for splitting 1 gram of CO2. However, the latter figure, as you may have noticed, is clearly absurd, as you logically cannot split 1 gram of CO2 with such a relatively low temperature.

I clearly understand that I am following the wrong procedure, although it seems the logical one at first, until, of course you arrive at an unreasonable figure. How should I find the required temperature for splitting a certain quantity of a compound? Also, why is my procedure wrong, and what have I not understood correctly?

Finally, I have also considered using a set of ultracapacitors connected together as an option to splitting CO2, (already having considered the amount of ultracapacitors needed): for example, to achieve an energy of ~36.37kJ (to split 1 gram of CO2) I would need 20 ultracapacitors with (individually) a voltage of 2.7V and capacitance of 500 farads. Would it be possible to split CO2 using ultracapacitors, or is this procedure also wrong, and why?

Thanks in advance
 

Answers and Replies

  • #2
Charles Link
Homework Helper
Insights Author
Gold Member
4,536
1,932
1600 kJ/mole is ## 1.6 \cdot 10^6 \,J/(6.02 \cdot 10^{23})= 2.7 \cdot 10^{-18} \, J/ ##molecule. This will only be approximate, but with ## k_B=1.38 \cdot 10^{-23} \, J/K ##, the temperature ## T \approx 2 \cdot 10^5 ## to separate the ## CO_2 ## molecule into atoms by thermal means. ## \\ ## And putting the molecule into a strong electric field, such as between capacitor plates is not likely to separate it into components. The ## CO_2## molecule is electrically neutral and only slightly polar. It would not be affected appreciably by the voltage from two capacitor plates.
 
Last edited:
  • #3
However, if the CO2 was pressurized and turned into liquid, adding an electrolyte, would it be possible to split the CO2 into its components?

Edit: is the temperature (T): 2·105 the temperature required to split 1 molecule of CO2, in degrees kelvin? In addition, I now understand that your procedure is the correct one, but why exactly is my procedure wrong, (1600kJ/44g to get energy for 1 gram and then transform ~36.37kJ to celsius: 19.15 cº (which I know is wrong)), as it seems the most logical & proper one at first hand, and how to avoid these type of procedures on other concepts?
 
Last edited:
  • #4
Charles Link
Homework Helper
Insights Author
Gold Member
4,536
1,932
The calculation shows energy ## E=2.7 \cdot 10^{-18} ## Joules/molecule. At a temperature of ## T=200,000 \, K ##, thermal energy will break most of the bonds in these molecules. That is only an approximate calculation, and each of the bond energies will actually be 1/2 of what I used above. This is only approximate, but it basically says that ## CO_2 ## is a very stable molecule. One way of getting ## O_2 ## in a process with ## CO_2 ## is by photosynthesis: ## CO_2+H_2 O \rightarrow CH_2O+O_2 ##. There have recently been attempts to do this process artificially, but it hasn't yet been achieved on a large scale. See e.g. https://www.physicsforums.com/threads/breaking-down-carbon-dioxide.916913/#post-5778727
 

Related Threads on Bonding energy in compounds

  • Last Post
Replies
2
Views
2K
Replies
3
Views
1K
Replies
6
Views
2K
  • Last Post
Replies
1
Views
1K
Replies
2
Views
765
  • Last Post
Replies
1
Views
3K
Replies
1
Views
966
  • Last Post
Replies
0
Views
2K
  • Last Post
Replies
1
Views
2K
Top