Understanding the Clausius-Clapeyron Formula: V_{l} and V_{g}

[Sebas4]

Hey, I have a question about the meaning of a variable in the Clausius-Clapeyron formula.

My textbook (Daniel v. Schroeder) says that the Clausius-Clapeyron formula is (for phase boundary between liquid and gas)
\frac{dP}{dT} = \frac{L}{T\left(V_{g} - V_{l} \right)}.

What is V_{l} or V_{g}? It's not volume. I looked on Wikipedia, they say that V_{g} - V_{l} is the difference in specific volume of gas and liquid.
Specific volume is defined as \nu = \rho^{-1}.

My question is, is V_{l} and V_{g} specific volumes for gas and liquid, or I mean is it correct?
I want to ask just to be sure.

Thank you in advance for responding,

-Sebas4.

 

[DrClaude]

What is V_{l} or V_{g}? It's not volume.

It is volume. Schroeder writes the equation in terms of extensive quantities (total latent heat for a given system of a given size) whereas in Wikipedia the equation is written in terms of the specific latent heat and the specific volume.

 

[Chestermiller]

L and V's in your equation are per mole.

 

[mjc123]

It doesn't matter as long as you are consistent, i.e. L and V are both specific (J/kg and m³/kg), or both molar (J/mol and m³/mol), or both extensive (J and m³). In each case the expression has units J m^-3 K^-1 ≡ Pa K^-1.