# Homework Help: Triple Point Determination

1. Nov 17, 2008

### ktmtalker

1. The problem statement, all variables and given/known data 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.

2. Relevant equations
lnp(solid)= 29.411-(5893.5K/T)
lnp(liquid)=22.254-(3479.9K/T)

3. 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.

2. Nov 18, 2008

### weejee

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. Nov 18, 2008

### ktmtalker

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?