Triple Point Determination

In summary, the problem involves calculating the temperature and pressure at the triple point for uranium hexafluoride with a molecular weight of 352.02. The equations used are lnp(solid)= 29.411-(5893.5K/T) and lnp(liquid)=22.254-(3479.9K/T). The attempt at a solution involved using P= 1 atm and equating the two equations to solve for the temperature. However, there was a small difference in the calculated pressure values. It is suggested to equate the two equations since the triple point is where they intersect.
  • #1
ktmtalker
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Homework Statement

I need to calculate the temperature and pressure at the triple point. natural log of pressure of the liquid/solid: lnp(solid)= 29.411-(5893.5K/T) lnp(liquid)=22.254-(3479.9K/T). The compound is uranium hexafluoride, MW= 352.02. I do not believe the actual molecule matters to much, just the weight. pressure is in Pa.



Homework Equations


lnp(solid)= 29.411-(5893.5K/T)
lnp(liquid)=22.254-(3479.9K/T)


The Attempt at a Solution


I used P= 1 atm -->101.325kPa, and using the lnp(solid) equation determined a temperature. I then used that same temp in the lnp(liquid) to solve the other lnp equation. It did not go well. I am unsure on how to relate these two equations to the triple point. I should be able to grind through the math when I know how to relate it all.
 
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  • #2
Is there any reason you put P=1atm?

In my opinion, you should equate those two equations since the triple point is where they meet each other.
 
  • #3
I just assumed it to try and work through the problem. I also tried setting the two equal to each other after posting to determine the temp. The temp was 337.2, which i put into each respective equation to get the pressures. It worked well, but there was a small difference in the answer I got for the pressure. one was 1.522443*10^5, and the other was 1.523616*10^5. I believe these values are close enough to consider them the same, what do you think?
 

1. What is a triple point?

A triple point is a thermodynamic state at which a substance exists in equilibrium as a solid, liquid, and gas. It is the point at which the three phases coexist and have equal rates of evaporation and condensation.

2. How is the triple point determined?

The triple point is determined by measuring the temperature and pressure at which the three phases of a substance coexist in equilibrium. This can be done using specialized equipment such as a triple point cell.

3. Why is the triple point important in thermodynamics?

The triple point is important because it is a fixed point on a phase diagram where the behavior of a substance is well-defined. It is used as a reference point for calibrating temperature scales and as a basis for defining other thermodynamic properties.

4. Can the triple point be affected by external factors?

Yes, the triple point can be affected by changes in external factors such as pressure, temperature, and impurities. These can alter the equilibrium between the three phases and shift the triple point to a different location on the phase diagram.

5. What is the significance of the triple point in the study of phase transitions?

The triple point is significant in the study of phase transitions because it represents the unique combination of temperature and pressure at which three phases can coexist in equilibrium. It is a critical point for understanding the behavior of substances during phase changes and for predicting their properties under different conditions.

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