Enthelpy of formation at non standard conditions

In summary: However, it might be interesting to know this for other compounds where the standard state is not ideal.
  • #1
Julius
2
0
Hi,

I want to know the enthalpy of formation of Ga2O3 and Ga2O at low pressure (ultra high vacuum) and high temperature.

Temperature seems easy, but I'm not sure how to get the enthalpy values for low pressures.

Does anyone know if there are books with enthalpy - pressure diagrams of these compounds?

It should be also possible to calculate it from the value at atandard conditions using ∂H/∂P=(V−T∂/V∂T)dP, but one needs a PVT relation. For Ga2O maybe the van der Waals equation for non-ideal gases? And for Ga2O3?

Cheers,
Julius
 
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  • #2
When it comes to data and diagrams, best starting point is often a library - librarians are trained to know where to look for information (they may not know what it means, but they know where to look for it ;) ).
 
  • #3
If the Ga compounds are solid at the T and p in question, you can probably neglect them, as ##\int V dp## is very small due to V being small.
If they are gaseous, they are certainly described well by the ideal gas law which works best at low p and high T. So the pressure dependence vanishes, too, as ##V-T \partial V/\partial T=0## for an ideal gas.
 
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Likes Chestermiller
  • #4
Thank you for the replies! :)

Yes, at low pressures I can use the ideal gas law, but I need to start from standard atmosphere pressure, so I think i still need an other PVT relation, right?
 
  • #5
No, as T is high
 
  • #6
I pondered about this question a bit more and there occurred something to me: For gasses, the standard state is a hypothetical state where the ideal behaviour at infinitely low pressure is extrapolated to 1 atmosphere.
So you can assume ideal behaviour for the gas by definition.
This is not very relevant in your case as gasses at standard pressure and temperature usually behave quite ideally.
 

1. What is enthalpy of formation at non-standard conditions?

Enthalpy of formation at non-standard conditions refers to the amount of energy that is released or absorbed when one mole of a substance is formed from its constituent elements at a given temperature and pressure that is different from the standard conditions of 25°C and 1 atm.

2. Why is it important to consider non-standard conditions when calculating enthalpy of formation?

Non-standard conditions can affect the stability and reactivity of a substance, which in turn can impact its enthalpy of formation. Therefore, it is important to consider these conditions in order to accurately determine the enthalpy of formation of a substance in a specific environment.

3. How do non-standard conditions affect the enthalpy of formation?

Non-standard conditions such as temperature and pressure can change the energy requirements for a reaction to take place, thus affecting the enthalpy of formation. For example, a higher temperature may require more energy to be supplied for a reaction to occur, resulting in a higher enthalpy of formation.

4. Can enthalpy of formation at non-standard conditions be measured experimentally?

Yes, enthalpy of formation at non-standard conditions can be measured experimentally by using calorimetry techniques. This involves measuring the change in temperature of a reaction mixture and using the data to calculate the enthalpy of formation.

5. How is the enthalpy of formation at non-standard conditions used in practical applications?

The enthalpy of formation at non-standard conditions is used in various practical applications, such as in the design of chemical reactions and processes. It is also a crucial factor in determining the energy efficiency and sustainability of industrial processes.

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