Chapter Five: The Clapeyron-Clausius Equation
Chapter Listing
Home: Journey to the Clapeyron-Clausius Equation
Chapter One: The Gibbs Equation
Chapter Two: The Tds Equation
Chapter Three: The Maxwell Relations
Chapter Four: The Clapeyron Equation
Chapter Five: The Clapeyron-Clausius Equation
Experiment: Complete the Journey From Home: Fun Experiment!
Real World Applications: The Sky's the Limit with the Clapeyron-Clausius Equation
References: References
HELP GO BACK! - Chapter Four: The Clapeyron Equation
Clapeyron - Clausius Equation
Using what we have found in previous sections and some approximations, we can find the Clapeyron- Clausius equation.
Why is this useful?
It allows you to work out how saturation pressure changes with temperature.
Two key assumptions must be made and because of this, the equation is actually an approximation rather than a definite result. These assumptions are:
1) The vapor must be treated as an ideal gas. This means that
ν2 = RT/P
2) At low pressures, the lower value for specific volume can be ignored.
ν12 >> ν1 so ν12 = ν2
These can be substituted into the Clapeyron equation found in the previous section to give
Then, rearranging by moving the T's and P's to the same side, we get
Due to the fact we have P and T on opposing sides, we can integrate each side. This gives us the final equation.
In the equation, R = Universal gas constant, T = temperature (in Kelvin), P = pressure, h = enthalpy.
If you are not sure about any of these properties, you will be able to find more information on what they are on other pages on the allaboutthermofluids.com website.
Congratulations.
You have reached the end of your journey. But in order to make sure you have understood the journey, you must now complete the quiz.