# Homework Help: Thermodynamics question. Could be simpler than it looks, but I am really stuck.

1. Aug 26, 2010

### Jasbraman

Precisely what does the following equation, in which R is the gas constant, allow one to calculate?

ln xs = -dHf/R(T0-T/TT0)

I have no idea what this could be. I know what each part of the equation is (gas constant, change in enthalpy of formation, Freezing point depression etc.) I just don't know what it allows me to calculate...except that its the natural log of something. I think it has something to do with entropy, but I'm not sure. Any help would be much appreciated.

Last edited: Aug 26, 2010
2. Aug 27, 2010

### presbyope

Notation is ambiguous. Did you mean

$$\ln x_s = \frac{-dH_f}{R}\left(\frac{T_0-T}{TT_0}\right)$$

in which case $x_s$ is dimensionless?

3. Aug 29, 2010

### Jasbraman

That is exactly what I meant, yes. I did not know you could put in equations like that. Anyway, I have to find out precisely what it allows me to calculate, but I have no idea.

4. Aug 29, 2010

### presbyope

Try this:
1. the expression with T can be rewritten as two terms
2. exponentiate

Last edited: Aug 29, 2010
5. Aug 29, 2010

### presbyope

That should give you something that looks a lot like something else you're familiar with :-/

6. Aug 30, 2010

### Jasbraman

Oohhhhh yeeeah! Thanks for that!