# Stuck on integral!

1. Sep 6, 2008

### Riles246

1. The problem statement, all variables and given

integral of : (nRT)/(V-nb)dV from Vi to Vf

$$\int$$ $$^{Vf}_{Vi}$$ (nRT)/(V-nb)dV

I am really stuck on this one!
Do you need to move the denominator up first?

Last edited: Sep 6, 2008
2. Sep 6, 2008

### edziura

Assuming that everything except V is a constant for this problem, try the substitution

u = V -nb

3. Sep 6, 2008

### Defennder

You need to tell us which are constants and which are functions of V in this question. Otherwise, the problem becomes very simple when you factor nRT out.

4. Sep 6, 2008

### Riles246

Since the integral says "dV" doesn't that mean it only needs to be integrated with respect to the variable V while holding all other variables constant?

5. Sep 7, 2008

### physicsnoob93

Assuming everything else is constant.

factor the nRT out. Let u = V-nb.
du/dv = 1 if nb is a constant.
This means that when u differentiate the denominator u get the numerator and its safe to straightaway ln the denominator.

I think it should be ln|Vf-nb| - ln|Vi-nb|

i might be wrong though.

Btw, is it just a practice question or are u doing this for chem? just curious. ;).

6. Sep 7, 2008

### edziura

Also don't forget if you substitute u = V - nb, you must also write the limits of integration in terms of u.

7. Sep 8, 2008

### Riles246

I am doing these problems to touch up on my Calc for a class I am taking (physical chem)

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