How do you calculate the temp at which a H2O molecule splits into single atoms?

In summary, the person is looking to figure out the temperature at which hydrogen and oxygen will no longer combine due to extreme temperatures. They are hoping someone can help them out with this.
  • #1
achilles89
7
0
Hi

I want to figure out how to calculate the temperature at which more energy is required to keep hydrogen and oxygen together (as in the case of H2O) than to separate them...in other words the temperature at which hydrogen and oxygen will no longer combine due to extreme temperatures. How would I do this? I am not a math mozart so I would appreciate elaborate description and possibly external links too :)
 
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  • #3
...really? I've been scowering the web for over a week now..I too know how to use Google. I was hoping someone knew more about it.
 
  • #4
The only way to measure the temperature of decomposition is to heat the substance and check for decomposition products. There may be a way to do it using quantum mechanics but I have no clue how to do that.
 
  • #5
It should be possible to use thermodynamic data - calculate equilibrium constant as a function of temperature. It still requires experimental data.
 
  • #6
Thank you. I will just have to conduct some tests. Is it possible to predict such things with quantum mechanics?
 
  • #7
In theory, if you know the enthalpy change (ΔH) and entropy change (ΔS) associated with the reaction, you can calculate the temperature at which transforming breaking apart water is as favorable as forming water. This occurs when the change in free energy (ΔG) of the reaction is equal to zero, and because ΔG = ΔH - TΔS, it is easy to solve for this temperature.

However, this approach relies on the assumption that ΔH and ΔS do not change with temperature. While this assumption is good over fairly small ranges of temperature, I'm not sure how well they hold over larger ranges.

Edit: it is also possible to calculate equilibrium constants as well as some of the thermodynamic data from quantum mechanics. Statistical mechanics textbooks will have information on how to do that.
 
  • #8
What I am looking to do is determine the relative thermal point at which hydrogen and oxygen gases can exist together and not recombine into water. The experiment I am planning to perform involves thermal disassociation of H2O...however, in order to prevent an explosion due to additional water input, I wish to determine the minimum temperature above their autocombustion temperature at which they will not recombine due to thermal conditions.
Any thoughts?
 
  • #9
Only that dissociation at given temperature will also be favoured by low pressure, concentration, by rarefaction.
 

1. How is the temperature at which a H2O molecule splits into single atoms calculated?

The temperature at which a H2O molecule splits into single atoms is calculated using the Arrhenius equation, which takes into account the activation energy and rate constant of the reaction. The equation is as follows: T = (Ea/R) * ln(k/A), where T is the temperature in Kelvin, Ea is the activation energy, R is the gas constant, k is the rate constant, and A is a constant related to the frequency factor of the reaction.

2. What factors affect the temperature at which a H2O molecule splits into single atoms?

The temperature at which a H2O molecule splits into single atoms is affected by a number of factors, including the activation energy of the reaction, the concentration of reactants, the presence of a catalyst, and the pressure and temperature of the reaction environment. These factors can influence the rate of the reaction and therefore impact the temperature at which the reaction occurs.

3. Can the temperature at which a H2O molecule splits into single atoms be accurately predicted?

While the Arrhenius equation provides a theoretical calculation for the temperature at which a H2O molecule splits into single atoms, it is important to note that there are many variables and uncertainties that can affect the accuracy of this prediction. Factors such as impurities in the reaction environment and the presence of multiple reaction pathways can make it difficult to accurately predict the temperature at which the reaction will occur.

4. Is the temperature at which a H2O molecule splits into single atoms constant?

The temperature at which a H2O molecule splits into single atoms is not a fixed value, as it can vary depending on the conditions of the reaction. As mentioned before, factors such as concentration, pressure, and the presence of a catalyst can all influence the temperature at which the reaction occurs. Therefore, the temperature at which a H2O molecule splits into single atoms may not be constant and can change under different circumstances.

5. Why is it important to know the temperature at which a H2O molecule splits into single atoms?

Understanding the temperature at which a H2O molecule splits into single atoms is important for a number of reasons. It can provide insight into the kinetics and thermodynamics of the reaction, as well as help determine the most efficient conditions for the reaction to occur. This knowledge can also be useful in various industries, such as in the production of hydrogen gas through the electrolysis of water.

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